TY - CONF A1 - Kromm, Arne T1 - Influence of heat control on welding residual stresses in multi-layer component joints T2 - IIW Annual Assembly CY - Denver, CO, USA DA - 2012-07-09 PY - 2012 AN - OPUS4-26628 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - High-energy Synchrotron Study of the Stress-stain Behaviour of Hydrogen-charged High Strength Steel T2 - VISUAL-JW 2012 CY - Osaka, Japan DA - 2012-11-29 PY - 2012 AN - OPUS4-27309 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Schröpfer, Dirk T1 - From the Field to the Lab: Assessment of Residual Stresses in real-life Welded Components N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system specifically developed for this purpose with a maximum load capacity of 2 MN are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be simulated and quantified within the system. Additionally, X-ray diffraction can be applied to determine the resulting local residual stress distribution precisely with high spatial resolution. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. It was possible to clarify why elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of a heat treatment applied under mechanical stress resulting from welding is demonstrated by the example of a creep resistant steel. Reheat cracking is significantly increased in this case compared to small scale laboratory based tests. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Welding KW - Residual stress KW - Large scale test PY - 2018 AN - OPUS4-45978 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Schwingfestigkeitsverbesserung hochfester Schweißverbindungen mit Hilfe neuartiger LTT-Zusatzwerkstoffe N2 - Die Verwendung von LTT-Zusatzwerkstoffen stellt einen alternativen Ansatz zu den sonst üblichen Verfahren der Schweißnahtnachbehandlung zur Schwingfestigkeitserhöhung geschweißter Stahlkonstruktionen dar. Der wesentliche Wirkmechanismus beruht auf der Beeinflussung des Eigenspannungszustands durch die niedrige Martensitstarttemperatur bereits während des Schweißens. Dadurch werden die Druckeigenspannungen aus der behinderten Volumenausdehnung infolge Phasenumwandlung voll wirksam. Weiter weist die Schweißnaht eine hohe Härte auf, die die Schwingrissbildung verzögern kann, allerdings auch zu einer niedrigen Kerbschlagarbeit führt. Im ersten Teil dieses Beitrages werden grundlegende Untersuchungen zur schweißtechnischen Verarbeitung eines LTT-Zusatzwerkstoffes präsentiert. Dies beinhaltet zunächst die Sicherstellung der Schweißbarkeit sowie die Charakterisierung der Schweißgefüge und deren Härte mit dem Ziel, reproduzierbare Verbindungseigenschaften für die nachfolgende Schwingfestigkeitsprüfung herzustellen. Der zweite Teil des Beitrages beschäftigt sich mit den dazugehörigen Schwingfestigkeitsuntersuchungen an den Stählen S355J2 und S960Q unter Verwendung konventioneller Zusatzwerkstoffe im Vergleich zum LTT-Zusatz. Das verwendete Schweißdetail ist eine Verbindungsschweißung am Stumpfstoß unter Variation der Schweißnahtausführung (DY-Naht und V-Naht). Weitergehend wird eine bauteilähnliche Probe (die Längssteife) untersucht, bei der der LTT-Zusatzwerkstoff als zusätzliche Schweißlage aufgebracht wurde. Neben der Schwingfestigkeit werden die Schweißnähte hinsichtlich der Eigenspannungen, der Eigenspannungsstabilität im Schwingversuch sowie metallo-grafisch charakterisiert. Die Ergebnisse zeigen, dass LTT-Zusatzwerkstoffe unter Einhaltung wesentlicher Konstruktionsrichtlinien zu einem deutlichen Anstieg der Schwingfestigkeit führen. Dadurch kann das Leichtbaupotential hochfester Stahlgüten genutzt werden. T2 - DVS Congress CY - Friedrichshafen, Germany DA - 17.09.2018 KW - Eigenspannungen KW - Schwingfestigkeit KW - Hochfester Stahl KW - LTT PY - 2018 AN - OPUS4-45982 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schröpfer, Dirk A1 - Dixneit, Jonny A1 - Hannemann, Andreas A1 - Kannengießer, Thomas ED - Neu, Richard W. ED - Totten, George E. T1 - From the field to the lab: Real scale assessment of stresses in welded components N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system specifically developed for this purpose with a maximum capacity of 2 MN are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be simulated and quantified within the system. Additionally, X-ray diffraction can be applied to determine the resulting local residual stress distribution precisely with high spatial resolution. Two examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. It was possible to clarify why elevated working temperatures significantly increase the bending stresses in the welded joint and therefore the tensile residual stresses in the heat affected zone (HAZ). The effect of a heat treatment applied under mechanical stress resulting from welding is demonstrated by the example of a creep resistant steel. Reheat cracking is significantly increased in this case compared to small scale laboratory based tests. KW - Residual stress KW - Welding KW - Large-scale test KW - Creep resistant steel KW - High strength steel PY - 2018 DO - https://doi.org/10.1520/MPC20170111 SN - 2379-1365 VL - 7 IS - 4 SP - 574 EP - 593 PB - ASTM International CY - West Conchohocken AN - OPUS4-46662 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Formation of multi-axial welding stresses due to material behaviour during fabrication of high-strength steel components N2 - Today, an expanding application of high-strength steels in modern welded constructions can be observed. The economical use of these steel grades largely depends on the strength and reliability of the weldments. Therefore, the special microstructure and mechanical properties of these grades have to be taken into account by keener working ranges regarding the welding parameters. However, performance and safety of welded components are strongly affected by the stresses occurring during and after welding fabrication locally in the weld seam and globally in the whole component, especially if the shrinkage and distortion due to welding are restrained. Some extensive studies describe the optimization of the welding stresses and the metallurgical effects regarding an adapted welding heat control. Lower working temperatures revealed to be particularly effective to reduce the local and global welding-induced residual stresses of the complete weld significantly. However, decreased interpass temperatures cause concurrently higher stresses during welding fabrication. This work shows strategies to reduce these in-process stresses. With help of multi-axial welding stress analyses in component-related weld tests, using a special 2-MN-testing facility, differences in stress build-up are described in detail for root welds, filler layers and subsequent cooling to ambient temperature. KW - Residual stresses KW - GMA welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2018 DO - https://doi.org/10.1007/s40194-018-0650-2 SN - 0043-2288 SN - 1878-6669 VL - 63 IS - 1 SP - 43 EP - 51 PB - Springer AN - OPUS4-46604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dixneit, Jonny A1 - Kromm, Arne A1 - Boin, M. A1 - Wimpory, Robert A1 - Kannengießer, Thomas A1 - Gibmeier, J. A1 - Schröpfer, Dirk T1 - Residual stresses of LTT welds in large-scale components N2 - Residual stresses of welds become more and more important influencing cold cracking as well as the fatigue life of welded components. Low transformation temperature (LTT) filler materials offer the opportunity to alter the residual stresses already during the welding process by means of ad- justed martensite phase transformation temperature (MS). In the current paper, welding residual stresses are studied putting the focus on MS while joining heavy steel sections with a thickness of 20 and 25 mm, respectively. The residual stress state was determined at the top surface using X-ray diffraction as well as in the bulk by neutron diffraction. The results com- pare the residual stresses present in a conventional weld and LTT welds when multi-pass welding of large-scale compo- nents was applied. Repeated phase transformation in the case of the LTT weld is more vital for the residual stresses present in the real-life-like joints. This accounts for the top surface in longitudinal direction but is most pronounced for the bulk of the welds. Detrimental tensile residual stresses are mainly re- duced in the bulk in comparison to a conventional filler wire even in multi-pass welds of thick steel sections. T2 - IIW AA 2016 CY - Melbourne, Australia DA - 10.07.2016 KW - LTT KW - Welding residual stress KW - Phase transformation KW - Interpass temperature PY - 2017 DO - https://doi.org/10.1007/s40194-017-0502-5 SN - 0043-2288 SN - 1878-6669 VL - 61 IS - 6 SP - 1089 EP - 1097 PB - Springer CY - Heidelberg AN - OPUS4-41169 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Gibmeier, J. A1 - Genzel, C. A1 - Van der Mee, V. T1 - Determination of residual stresses in low transformation temperature (LTT -) welds metals using X-rayand high energy synchrotron radiation N2 - Crack and fatigue resistance are relevant evaluation criteria for welded joints and are decreased by tensile residual stresses resulting from the welding and cooling process, while compressive residual stresses can have a positive influence on the characteristics mentioned. In order to generate compressive residual stresses, a set of post weld treatment procedures is available, like shot peening, hammering, etc. These procedures have the disadvantage that they are time and cost extensive and have to be applied after welding. As another point, such technologies can only produce compressive stresses at the top surface, i.e. can only contribute to the reduction of the risk of cracks initiated at the surface, like fatigue cracks. A chance to generate compressive stresses over the complete weld joint during the welding procedure is offered by the so-called Low Transformation Temperature (LTT -) filler wires. Compared to conventional wires, these materials show lower phase transformation temperatures, which can work against coolingrelated tensile stresses, resulting from respective shrinkage restraint. In consequence, distinct compressive residual stresses can be observed within the weld and adjacent areas. The strength of these fillers makes them potentially applicable to high-strength steel welding. Welds produced with different LTT – filler wires have shown different levels and distributions of the resulting residual stresses depending on the specific transformation temperature. The transformation temperatures are determined by temperature measurement. Classical X-ray diffraction as well as diffraction methods using high energy synchrotron radiation have been used for residual stress analysis. By means of high energy synchrotron diffraction in reflection mode residual stress depth gradients can be determined nondestructively. The phase selective nature of the diffraction measurements enables the simultaneous determination of the phase specific residual stresses of all contributing crystalline phases within one experiment. The application of white beam diffraction implies recording of a multitude of diffraction lines within the energy range of the provided energy spectrum of the white beam. By this means phase specific residual stress depth distributions up to distances of 150 ìm below the surface can be analysed for steel using the energy dispersive set-up of the HMI-beamline EDDI at the Bessy site, Berlin, providing an energy range between 20-150 keV. As a side effect quantitative phase analysis can be carried out using white energy dispersive diffraction e.g. the determination of the content of retained austenite in the weld. KW - Filler materials KW - Low temperature KW - Reference lists KW - Residual stresses KW - Temperature KW - Transformation KW - Synchrotron radiation KW - Phase specific residual stresses KW - Energy dispersive diffraction PY - 2009 SN - 0043-2288 SN - 1878-6669 VL - 53 IS - 1/2 SP - 3 EP - 16 PB - Springer CY - Oxford AN - OPUS4-19214 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Umwandlungsverhalten und Eigenspannungen beim Schweißen neuartiger martensitischer Low Transformation Temperature - Zusatzwerkstoffe T2 - 23. WAW-Nachwuchssitzung CY - Berlin, Germany DA - 2008-11-27 PY - 2008 AN - OPUS4-19294 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Umwandlungsverfahren und Eigenspannungen beim Schweißen neuartiger martensititscher Low Transformation Temperature - Zusatzwerkstoffe T2 - BAM-Kolloquium CY - Berlin, Germany DA - 2008-09-03 PY - 2008 AN - OPUS4-19295 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Phase Transformations of Different LTT Alloys and their Effect on Residual Stresses and Cold Cracking T2 - IIW Intermediate Meeting - Commission IX CY - Brussels, Belgium DA - 2009-03-19 PY - 2009 AN - OPUS4-19171 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Wasserstoffunterstützte Risse an hochfesten Feinkornbaustählen T2 - 11. Gefahrgut-Technik-Tage CY - Berlin, Germany DA - 2008-11-20 PY - 2008 AN - OPUS4-19293 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - RPRT A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Characterising Phase Transformations of Different LTT Alloys and their Effect on Residual Stresses and Cold Cracking N2 - Novel martensitic filler materials with specially adjusted martensite start temperatures (Ms) can counteract the cooling specific shrinkage due to expansion effects of the weld metal associated with phase transformations. That can be exploited to create compressive residual stresses in the weld and adjacent areas, i.e. beneficial for increasing fatigue strength. The Ms temperature is shifted via the chemical composition, mainly by the alloying elements nickel and chromium, resulting as well in different retained austenite contents. Investigations were made using different Low Transformation Temperature (LTT) alloys with varying nickel content. The resulting phase transformation temperatures were - for the first time - detected using high energy synchrotron diffraction and Single Sensor Differential Thermal Analysis (SS-DTA). Compared to angle dispersive diffraction, energy dispersive diffraction offers the possibility to measure residual stresses of the martensite and austenite phase parallel fast in one experiment up to depths of 100 µm. The residual stresses show significant distributions dependent on Ms temperature. The effect on the cold cracking behaviour of these alloys was investigated using the Tekken test. Results show that cold cracking can be avoided when appropriate contents of retained austenite are existent. PY - 2009 IS - IX-2311-09 SP - 1 EP - 9 PB - International Institute of Welding CY - Paris AN - OPUS4-19749 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Stress build up in low transformation temperature filler material under defined restraint conditions T2 - JOM-15 Fifteenth International Conference on the Joining of Materials CY - Helsingor, Denmark DA - 2009-05-04 PY - 2009 AN - OPUS4-19388 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - In-Situ of the Residual Stress Stability of Low Transformation Temperature (LTT)-Filler Materials T2 - 1st International Workshop "In-Situ with Photons, Neutrons and Electrons Scattering" CY - Berlin, Germany DA - 2009-09-01 PY - 2009 AN - OPUS4-19845 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - In-Situ Observation of Phase Transformations during Welding of low Transformation Temperatur Filler Material T2 - THERMEC 2009 International Conference on Processing & Manufactoring of Advanced Materials Processing, Fabrication, Properties, Applications CY - Berlin, Germany DA - 2009-08-25 PY - 2009 AN - OPUS4-19869 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - In-Situ Studies of Phase Transformation an Residual Stresses in LTT Alloys During Welding Using Synchrotron Radiation T2 - 1st Inernational Workshop "In-Situ Studies with Photons, Neutrons an Electrons Scattering", BAM CY - Berlin, Germany DA - 2009-09-01 PY - 2009 AN - OPUS4-19868 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Gibmeier, J. T1 - In-situ observation of phase transformations during welding of low transformation temperature filler material KW - LTT filler material KW - In-situ observation KW - Energy dispersive diffraction KW - Transformation temperature KW - Residual stress PY - 2010 DO - https://doi.org/10.4028/www.scientific.net/MSF.638-642.3769 SN - 0255-5476 VL - 638-642 SP - 3769 EP - 3774 PB - Trans Tech Publications CY - Aedermannsdorf, Switzerland AN - OPUS4-20725 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Altenkirch, J. T1 - In-situ Synchrotron-Beugungsuntersuchungen zur Umwandlungskinetik und zur Dehnungsentwicklung beim Lichtbogenschweißen T2 - Arbeitsgemeinschaft Wärmebehandlung und Werkstofftechnik e.V., AWT Fachausschuss 13 Eigenspannungen CY - Stuttgart, Germany DA - 2009-11-04 PY - 2009 AN - OPUS4-20968 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Anwendung des neuen Controlled Tensile Weldability (CTW) Tests zur Untersuchung der Heißrissneigung T2 - Tagung Werkstoffprüfung CY - Bad Neuenahr, Germany DA - 2009-12-07 PY - 2009 AN - OPUS4-20658 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Brauser, Stephan A1 - Kromm, Arne T1 - Synchrotron diffraction for in-situ characterizations of materials behaviour T2 - 3rd Inter-university research seminar (IURS 2010) - Advances in welding and joining CY - Pusan, Korea DA - 2010-05-13 KW - In-situ diffraction KW - Phase transformation KW - High strength steel KW - Residual stress PY - 2010 SP - 127 EP - 131 CY - Pusan, Korea AN - OPUS4-21352 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - In situ phase characterization of low transformation temperature (LTT) alloy by means of synchrotron diffraction N2 - Cold cracking resistance is a relevant evaluation criterion for welded joints and affected by residual stresses which result from the welding procedure. Compressive residual stresses can thereby have a positive influence on preventing cracking. A unique possibility of generating compressive residual stresses already during the welding procedure is offered by the socalled Low Transformation Temperature (LTT) filler wires. Compared to conventional wires, these materials show decreased phase transformation temperatures which can work against the cooling-specific contraction. In consequence, distinct compressive residual stresses can be observed within the weld and adjacent areas. The strength of these fillers makes them potentially applicable to high-strength steel welding. Investigations were carried out to determine the phase transformation behaviour of different LTT-filler materials. Transformation temperatures were identified using Single Sensor Differential Thermal Analysis (SS-DTA). Additionally Synchrotron radiation was used to measure the transformation kinetics of all involved crystalline phases during heating and cooling of a simulated weld thermal cycle. KW - In-situ phase analysis KW - Energy dispersive diffraction KW - Phase transformation PY - 2010 SN - 1684-579X VL - 5 IS - 158 SP - 17 EP - 23 PB - Izdat. Masinostroenie CY - Moskva, Russia AN - OPUS4-21829 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Lausch, Thomas A1 - Kromm, Arne T1 - Effects of heat control on the stress build up during high strength steel welding under defined restraint conditions T2 - International Conference on high strength steels for hydropower plants CY - Takasaki, Japan DA - 2009-07-20 KW - Welding KW - Heat control KW - Stress build up KW - High-strength steel KW - Restraint intensity PY - 2009 UR - http://www-it.jwes.or.jp/proceedings/en/3-10.pdf SP - 10-1 - 10-8 AN - OPUS4-22317 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne T1 - In-situ studiesof phase transformation and residual stress build up in martensitic materials using synchrotron radiation T2 - 2nd IURS - Inter-university research symposium CY - Canmore, Alberta, Canada DA - 2009-05-20 KW - In-situ diffraction KW - Phase transformation KW - LTT alloy KW - Residual stress PY - 2009 IS - Paper 12 SP - 1 EP - 5 AN - OPUS4-22499 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Lausch, Thomas A1 - Kromm, Arne T1 - Effects of heat control on the stress build up during high-strength steel welding under defined restraint conditions T2 - 62nd IIW Annual assembly and conference CY - Singapore DA - 2010-07-12 KW - Welding KW - Heat control KW - Stress build up KW - High-strength steel KW - Restraint intensity PY - 2009 IS - IIW Doc IX-2316-09 (IX-L-1055-09) SP - 1 EP - 8 AN - OPUS4-22316 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Brauser, Stephan T1 - Synchrotron diffraction for visualization of solid state phase transformations T2 - VISUAL-JW 2010 - The international symposium on visualization in joining & welding science through advanced measurements and simulation CY - Osaka, Japan DA - 2010-11-11 KW - Synchrotron KW - EDXRD KW - Martensite KW - Residual stress KW - TRIP steel KW - Phase transformation PY - 2010 IS - MTJW-1 SP - 123 EP - 124 AN - OPUS4-22653 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - In-Situ EDXRD zur Eigenspannungsentwicklung beim Lichtborgenschweißen T2 - AWT Fachausschuss 13 Eigenspannungen, Arbeitsgemeinschaft Wärmebehandlung und Werksofftechnik e. V. CY - Karlsruhe, Germany DA - 2011-04-12 PY - 2011 AN - OPUS4-23564 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kromm, Arne A1 - Kannengießer, Thomas ED - Borsutzki, M. T1 - Anwendung des neuen Controlled Tensile Weldability (CTW) Tests zur Untersuchung der Heißrissneigung T2 - Tagung Werkstoffprüfung 2006 CY - Bad Neuenahr, Deutschland DA - 2006-12-07 KW - Heißrisstest KW - 1.4565 KW - Heißrissneigung KW - Dehnung KW - Dehngeschwindigkeit KW - Heißriss KW - Erstarrungsriss KW - Konstruktiver Einfluss PY - 2006 SN - 3-514-00734-9 SP - 451 EP - 456 PB - Stahleisen CY - Düsseldorf AN - OPUS4-14362 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - CT-02 In-situ-phase analysis using synchrotron radiation of low transformation temperature (LTT) welding material T2 - IIW International Congress, 2nd Latin American Welding Congress, XXXIV Consolda - National Welding Congress CY - Sao Paulo, Brazil DA - 2008-05-18 PY - 2008 SN - 85-8718210-2 SP - 1 EP - 12 AN - OPUS4-18591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne T1 - CT-01 Formation of welding residual stresses in low transformation temperature (LTT) materials T2 - IIW International Congress, 2nd Latin American Welding Congress, XXXIV Consolda - National Welding Congress CY - Sao Paulo, Brazil DA - 2008-05-18 PY - 2008 SN - 85-8718210-2 SP - 1 EP - 12 AN - OPUS4-18590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - In-situ-phase analysis using synchroton radiation of low transformation temperature (LTT) welding material T2 - IIW International Congress, 2nd Latin American Welding Congress, XXXIV CONSOLDA-National Welding Congress CY - São Paulo, Brazil DA - 2008-05-18 PY - 2008 AN - OPUS4-17812 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Characterizing phase transformations of different LTT alloys and their effect on residual stresses and cold cracking N2 - Novel martensitic filler materials with specially adjusted martensite start temperatures (Ms) can counteract the cooling specific shrinkage due to expansion effects of the weld metal associated with phase transformations. That can be exploited to create compressive residual stresses in the weld and adjacent areas, i.e. beneficial for increasing fatigue strength. The Ms-temperature is shifted via the chemical composition, mainly by the alloying elements nickel and chromium, resulting as well in different retained austenite contents. Investigations were made using different Low Transformation Temperature (LTT) alloys with varying nickel content. The resulting phase transformation temperatures were — for the first time — detected using high energy synchrotron diffraction and Single Sensor Differential Thermal Analysis (SS-DTA). Compared to angle dispersive diffraction, energy dispersive diffraction offers the possibility to measure residual stresses of the martensite and austenite phase parallel fast in one experiment up to depths of 100 μm. The residual stresses show significant distributions dependent on the Ms-temperature. The effect on the cold cracking behaviour of these alloys was investigated using the Tekken test. Results show that cold cracking can be avoided when appropriate contents of retained austenite are existent. KW - Austenite KW - Cold cracking KW - Martensite KW - Low KW - Temperature KW - Transformation PY - 2011 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 03/04 SP - 48 EP - 56 PB - Springer CY - Oxford AN - OPUS4-23402 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Lausch, Thomas A1 - Kromm, Arne T1 - Effects of heat control on the stress build-up during high-strength steel welding under defined restraint conditions N2 - Realization and safe operation of modern welded structures are progressively requiring for base and filler materials to cope with continually increasing loads, Analyses with a view to crack prevention therefore need to accommodate particularly the structural design (restraint intensity) and the thermomechanical effects in terms of stresses introduced during welding, Against this background, multi-run welding experiments were carried out in an IRC - (Instrumented Restraint Cracking) Test under defined restraint intensity in order to examine the influence of heat control (preheating and interpass temperatures) on the weldinq-specific forces and stresses, The experiments revealed significant rises in the reaction force and stress after welding with increasing preheating and interpass temperature, Furthermore, various concepts for calculating the preheating temperature are discussed, It is demonstrated that the hitherto existing concepts for high-strength finegrained structural steels can lead to divergent results. KW - Cracking KW - Heat KW - High strength steels KW - Restraint KW - Stress KW - Testing PY - 2011 SN - 0043-2288 SN - 1878-6669 VL - 55 IS - 07/08 SP - 58 EP - 65 PB - Springer CY - Oxford AN - OPUS4-24294 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Altenkirch, J. A1 - Gibmeier, J. A1 - Kostov, V. A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Doyle, S. A1 - Wanner, A. T1 - Time- and temperature-resolved synchrotron X-ray diffraction: observation of phase transformation and strain evolution in novel low temperature transformation weld filler materials N2 - Solid-state phase transformations and the evolution of thermal and elastic strains in novel low temperature transformation (LTT) weld filler materials in the near surface region are monitored in real time by means of an innovative experimental set-up at the PDIFF (powder diffraction) beamline at the synchrotron light source ANKA (Angströmquelle Karlsruhe) at the KIT (Karlsruhe Institute for Technology). The key components of the diffraction set-up are two fast microstrip line detectors, which enables the strain evolution to be followed as a function of time and temperature for a 0.5?s counting time. During controlled heating and cooling cycles, as well as during near welding cycles, the martensite–austenite–martensite phase transitions are analysed. The transformation kinetics are monitored during resistance heating of small chips of the pure LTT alloys and during gas tungsten arc welding of simplified LTT welds using a specially designed welding rig for in-situ studies on the diffraction instruments. Under the mechanically unconstrained condition allowing free thermal expansion and shrinkage, the LTT alloys are found to exhibit decreasing transformation temperatures Ac and MS and increasing phase fraction of retained austenite for increasing Ni content. The strain evolution during welding reveals increased compressive stresses upon welding, which is attributed to the martensite formation upon cooling, which counteracts the thermal contraction strains. Comparison of the transformation temperatures reveals higher values than in the pure LTT alloys, but no variation between the different alloys. On the one hand, this is attributed to preferred grain orientation affecting the diffraction measurements and the determination of the transformation temperatures. On the other hand, it is possible that with the different chemical compositions of the LTT alloys and the mechanical constraints during welding, the evolution of the residual strain and stress may vary and result in counteracting affects with respect to lowered martensite start temperatures. KW - In-situ synchrotron X-ray diffraction KW - Low temperature transformation KW - Welding PY - 2011 DO - https://doi.org/10.1177/0309324711413190 SN - 0309-3247 SN - 2041-3130 VL - 46 IS - 7 SP - 563 EP - 579 PB - Sage CY - London AN - OPUS4-24683 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Influence of Heat Control on Welding Residual Stresses in Multi-layer Component Joints T2 - IIW Intermediate Meeting 2012 CY - Cambridge, England DA - 2012-02-20 PY - 2012 AN - OPUS4-25539 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Kurzvorstellung des Projektes H2SuD / Wasserstoff und Schweißen Einfluss des Schweißens auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2 Gasleitungen N2 - Die Wasserstoffinfrastruktur ist eine zentraler Bestandteil der erfolgreichen Umsetzung der wasserstoffbasierten Energiewende. Dabei bilden Ferngasleitungen quasi das "Rückgrat" der Transportinfrastruktur großer Gasmengen. Dabei müssen unter Umständen Reparaturen an den Pipelines durchgeführt werden. Dabei ist in der Erdgasinfrastruktur das Schweißen an in Betrieb befindlichen (d.h. von Gas durchflossenen) Pipelines Stand der Technik. Es ist jedoch vollkommen offen, inwieweit diese Technik auf die reine Wasserstoffpipelines übertragbar sind. Hierzu leistet das Projekt H2SuD wichtige Beiträge zur Aufklärung des Einfluss eines Reparaturschweißprozesses auf die Wasserstoffaufnahme und Degradation im Betrieb befindlicher H2 Gasleitungen. T2 - Sitzung des DIN-Gemeinschaftsarbeitsausschusses NA 092 00 05 GA, NAS/NMP: Zerstörende Prüfung von Schweißverbindungen CY - Berlin, Germany DA - 15.03.2023 KW - Wasserstoff KW - Pipeline KW - Reparatur KW - Schweißen PY - 2023 AN - OPUS4-57169 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Liepold, Philipp A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Einfluss des Einspanngrades auf die Bildung von Erstarrungsrissen in Überlappverbindungen hochfester Stähle N2 - Im Beitrag werden Ergebnisse aus Versuchen mit dem Controlled Thermal Severity (CTS)-Test vorgestellt, der für sehr stark eingespannte Kehlnähte bekannt ist. Niedriglegierte Schweißungen an hochfesten Stählen sind nicht anfällig für Erstarrungsrissbildung. Unter dem besonderen Einfluss eines hohen Einspanngrades wurde die Erstarrungsrissneigung durch Abmessen der Rissflächen als Funktion der Schweißparameter und des Einspanngrades für vier hochfeste Schweißzusätze im MAG-Schweißen untersucht. Die Tests zeigen, dass sowohl eine Erhöhung des Einspanngrades als auch eine Änderung der Schweißparameter (hinsichtlich Streckenenergie und Geschwindigkeit) zu mehr Erstarrungsrissfläche führen. Besonders die Kombination aus sehr hohem Einspanngrad und hoher Streckenenergie plus hoher Schweißgeschwindigkeit sollte im Sinne der Erstarrungsrissminimierung vermieden werden. T2 - DVS-Congress CY - Erfurt, Germany DA - 16.09.2024 KW - CTS KW - Erstarrungsrisse KW - Kehlnähte PY - 2024 VL - 2024 SP - 193 EP - 200 AN - OPUS4-61069 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten A1 - Engelking, Lorenz A1 - Schröpfer, Dirk A1 - Scharf-Wildenhain, Ronny A1 - Hälsig, Andre A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Fertigungsbedingte Beanspruchungen und Kaltrisssicherheit in generativ gefertigten Bauteilen aus hochfesten Feinkornbaustählen N2 - Additive Fertigungsverfahren wie das Direct Energy Deposition-Arc (DED-Arc) oder Wire Arc Additive Manufacturing (WAAM) ermöglichen die effiziente Herstellung gewichtsoptimierter, endkonturnaher Bauteile im modernen Stahlbau. Steigerungen der Effizienz können durch den Einsatz hochfester Stähle erreicht werden, insbesondere durch Verringerung von Wandstärken und Bauteilgewicht sowie signifikante Einsparung von Kosten, Zeit und Ressourcen. DED-Arc Schweißzusatzwerkstoffe sind bereits auf dem Markt verfügbar, allerdings fehlen Richtlinien und quantitative Kenntnisse über die schweißbedingte Beanspruchung während der Fertigung und im Betrieb, welche den industriellen Einsatz stark limitieren. In einem gemeinsamen Projekt der BAM und der Technischen Universität Chemnitz wurden die wesentlichen Einflüsse und komplexen Wechselwirkungen von Werkstoff, Fertigungsverfahren, Konstruktion und Bearbeitungsschritten auf die Eigenspannungen untersucht. Ziel war es, den stahlverarbeitenden Anwendern, insbesondere KMU, eine risssichere und beanspruchungsgerechte Herstellung und Modifizierung von Bauteilen und Halbzeugen aus hochfesten Feinkornbaustahl unter Verwendung MSG-basierter generativer Verfahren zu ermöglichen. T2 - DVS Innovationstage 2024 CY - Düsseldorf, Germany DA - 10.04.2024 KW - Wire Arc Additive Manufacturing (WAAM) KW - Feinkornbaustähle KW - Additive Fertigung KW - Kaltrisssicherheit KW - Direct Energy Deposition-Arc (DED-Arc) PY - 2024 SP - 96 EP - 104 AN - OPUS4-61932 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - WAAM process influences on local microstructure and residual stresses in high-strength steels N2 - High-strength fine-grain structural steels have great potential for weight optimization of many modern engineering structures. Efficient manufacturing can be achieved here above all by Wire Arc Additive Manufacturing (WAAM). First commercial high-strength welding consumables for WAAM are already available. Due to a lack of knowledge and guidelines for the industry regarding welding residual stresses and component safety in manufacturing and operation, their application is still severely limited. Residual stresses play a crucial role here, as the special microstructure of high-strength steels is sensitive to cold cracking. For this reason, process- and material-related influences, as well as the design effects on residual stress formation, are being investigated in a project funded by the AiF (FOSTA P1380/IGF 21162 BG). This study focuses on determining the interactions between heat control during WAAM process, resulting hardness, microstructure, and residual stresses, analyzed by X-ray diffraction. Welding experiments using geometrically similar AM specimens show that, with regard to the heat input, the energy per unit length in particular leads to significantly affected cooling times and microstructures and causes pronounced localized effects in terms of residual stresses in the upper weld beads. T2 - 46th MPA-Seminar CY - Stuttgart, Germany DA - 12.10.2021 KW - Wire Arc Additive Manufacturing KW - High-strength structural steels KW - Vickers hardness KW - Residual stresses PY - 2021 VL - 46 SP - 296 EP - 306 PB - MPA-Stuttgart AN - OPUS4-53571 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Einfluss der Wärmeführung auf die Eigenschaften und fertigungsbedingten Beanspruchungen additiv geschweißter hochfester Feinkornbaustähle N2 - Hochfeste Feinkornbaustähle verfügen über ein großes Potenzial für gewichtsoptimierte, effiziente Strukturen in vielen modernen Stahlkonstruktion. Weitere Effizienzsteigerungen können durch additives Fertigen sowie bionische Bauweisen erreicht werden. Kommerzielle hochfeste Zusatzwerkstoffe für additives MSG-Schweißen (engl.: Wire Arc Additive Manufacturing, WAAM) sind bereits von den Schweißzusatzherstellern lieferbar. Derzeit ist jedoch eine breite industrielle Anwendung insbesondere für KMU aufgrund fehlender quantitativer Erkenntnisse und Richtlinien bezüglich schweißbedingter Beanspruchungen und Bauteilsicherheit während der Herstellung und des Betriebs stark limitiert. In einem gemeinsamen Forschungsprojekt (FOSTA-P1380/IGF21162BG) der BAM und der TU Chemnitz werden die mit Eigenspannungsausbildung und der Gefahr einer Kaltrissbildung verbundenen prozess- und werkstoffbedingten sowie konstruktiven Einflüsse untersucht. Im Fokus dieser Analysen steht die Bestimmung der Wechselwirkungen zwischen WAAM-Prozessparametern bzw. der Wärmeführung auf das Gefüge und die Eigenspannungen. Hierfür werden Referenzproben als offene Hohlquader mit definierten Abmessungen vollautomatisiert mit einem speziellen, hochfesten WAAM-Massivdraht (Streckgrenze >790 MPa) geschweißt. Die gezielte Einstellung der geometrischen Eigenschaften erfolgt durch Schweißparameter und Nahtaufbau bei ca. 4 kg/h mittlerer Abschmelzleistung. Die Wärmeführung wird innerhalb eines statistischen Versuchsplanes mittels Streckenenergie (200 kJ/m bis 650 kJ/m) und Zwischenlagentemperatur (100 °C bis 300 °C) so variiert, dass die t8/5-Abkühlzeiten dem empfohlenen Verarbeitungsbereich entsprechen (ca. 5 s bis 20 s). Ziel ist es bei konstanten geometrisch-konstruktiven Randbedingungen, den Einfluss der Wärmeführung auf Gefüge und resultierende Eigenspannungen zu analysieren. Für die Streckenenergie können neben den Gefügeeinflüssen aufgrund der resultierenden Abkühlzeit deutliche Effekte insbesondere auf die lokalen Eigenspannungen im Bauteil belegt werden. Das Schweißen mit zu hoher Wärmeeinbringung bzw. Abschmelzleistung kann zu ungünstigen Gefüge- und Bauteileigenschaften führen, gleichzeitig jedoch niedrigere Zugeigenspannungsniveaus bewirken. Solche komplexen Wechselwirkungen gilt es letztlich mit diesen Untersuchungen zu klären, um leicht anwendbare Verarbeitungsempfehlungen und Normvorgaben für ein wirtschaftliches, anforderungsgerechtes und risssicheres WAAM von hochfesten Stählen den Anwendern zur Verfügung zu stellen. T2 - DVS Congress 2021 CY - Online meeting DA - 14.09.2021 KW - MAG-Schweißen KW - Hochfester Stahl KW - Eigenspannungen KW - Additive Fertigung KW - Kaltrisssicherheit PY - 2021 SN - 978-3-96144-146-4 VL - 371 SP - 16 EP - 22 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-56669 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Scharf-Wildenhain, R. A1 - Hälsig, A. A1 - Härtel, S. A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Einfluss der Wärmeführung auf die Eigenschaften und fertigungsbedingten Beanspruchungen additiv geschweißter hochfester Feinkornbaustähle N2 - Hochfeste Feinkornbaustähle verfügen über ein großes Potenzial für gewichtsoptimierte, effiziente Strukturen in vielen modernen Stahlkonstruktion. Weitere Effizienzsteigerungen können durch additives Fertigen sowie bionische Bauweisen erreicht werden. Kommerzielle hochfeste Zusatzwerkstoffe für additives MSG-Schweißen (engl.: Wire Arc Additive Manufacturing, WAAM) sind bereits von den Schweißzusatzherstellern lieferbar. Derzeit ist jedoch eine breite industrielle Anwendung insbesondere für KMU aufgrund fehlender quantitativer Erkenntnisse und Richtlinien bezüglich schweißbedingter Beanspruchungen und Bauteilsicherheit während der Herstellung und des Betriebs stark limitiert. In einem gemeinsamen Forschungsprojekt (FOSTA-P1380/IGF21162BG) der BAM und der TU Chemnitz werden die mit Eigenspannungsausbildung und der Gefahr einer Kaltrissbildung verbundenen prozess- und werkstoffbedingten sowie konstruktiven Einflüsse untersucht. Im Fokus dieser Analysen steht die Bestimmung der Wechselwirkungen zwischen WAAM-Prozessparametern bzw. der Wärmeführung auf das Gefüge und die Eigenspannungen. Hierfür werden Referenzproben als offene Hohlquader mit definierten Abmessungen vollautomatisiert mit einem speziellen, hochfesten WAAM-Massivdraht (Streckgrenze >790 MPa) geschweißt. Die gezielte Einstellung der geometrischen Eigenschaften erfolgt durch Schweißparameter und Nahtaufbau bei ca. 4 kg/h mittlerer Abschmelzleistung. Die Wärmeführung wird innerhalb eines statistischen Versuchsplanes mittels Streckenenergie (200 kJ/m bis 650 kJ/m) und Zwischenlagentemperatur (100 °C bis 300 °C) so variiert, dass die t8/5-Abkühlzeiten dem empfohlenen Verarbeitungsbereich entsprechen (ca. 5 s bis 20 s). Ziel ist es bei konstanten geometrisch-konstruktiven Randbedingungen, den Einfluss der Wärmeführung auf Gefüge und resultierende Eigenspannungen zu analysieren. Darüber hinaus erfolgt die Bestimmung des Einflusses der t8/5-Abkühlzeit auf die mechanisch-technologischen Eigenschaften des speziellen, hochfesten WAAM-Massivdrahts mithilfe von Dilatometeranalysen. Für die Streckenenergie können neben den Gefügeeinflüssen aufgrund der resultierenden Abkühlzeit deutliche Effekte insbesondere auf die lokalen Eigenspannungen im Bauteil belegt werden. Das Schweißen mit zu hoher Wärmeeinbringung bzw. Abschmelzleistung kann zu ungünstigen Gefüge- und Bauteileigenschaften führen, gleichzeitig jedoch niedrigere Zugeigenspannungsniveaus bewirken. Die Dilatometeranalysen zeigen für den untersuchten WAAM-Schweißzusatzwerkstoff eine großes t8/5-Zeitfenster mit einer vergleichsweise geringen Abnahme der Zugfestigkeit mit zunehmender t8/5-Abkühlzeit. Solche komplexen Wechselwirkungen gilt es letztlich mit diesen Untersuchungen zu klären, um leicht anwendbare Verarbeitungsempfehlungen und Normvorgaben für ein wirtschaftliches, anforderungsgerechtes und risssicheres WAAM von hochfesten Stählen den Anwendern zur Verfügung zu stellen. T2 - 42. Assistentenseminar Fügetechnik CY - Brunswick, Germany DA - 06.10.2021 KW - MAG-Schweißen KW - Hochfester Stahl KW - Eigenspannungen KW - Additive Fertigung KW - Kaltrisssicherheit PY - 2022 SN - 978-3-96144-210-2 VL - 385 IS - 42 SP - 94 EP - 101 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-56642 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stresses and hydrogen assisted cracking in thick walled submerged arc weld joints for offshore applications N2 - Offshore wind turbines continuously increase in size and weight and demand adequate offshore foundations concepts like monopiles, tripods or jackets. These components are typically submerged arc welded (SAW) high-strength thick steel plates like the S420ML. During welding, the occurrence of delayed hydrogen assisted cracking (HAC) must be anticipated. HAC is a critical combination of the local hydrogen concentration within a susceptible microstructure under certain mechanical load, i.e., the occurring (welding) residual stresses. The welding sequence of the thick-walled plates complicate the residual stress distribution due to the necessary repeated thermal cycling, i.e., welding seam / layer deposition to fill the joint. For that purpose, SAW with two-wire-technique was used to weld a specially designed and prototype-like mock-up of a real component with a thickness of 50 mm, filled with 22 passes and a seam length of 1,000 mm. Additional welded stiffeners simulated the effect of a high restraint, to stimulate critical HAC conditions. The residual stresses were determined by a robot XRD goniometer. A least square regression analysis of the sin²ψ-law by using multiple ψ- and φ-tilts was applied. Tensile residual stresses up to the yield limit are found both in the weld metal and in the heat-affected zone. Numerical modelling allowed the qualitative estimation of the hydrogen diffusion in the weld, enabling the determination of critical conditions for the formation of HAC. In a future step, a structural simulation will allow the assessment of the welding residual stresses and the comparison to the XRD-values. T2 - International Conference on Residual Stresses ICRS-11 CY - Nancy, France DA - 27.03.2022 KW - Welding KW - X-ray diffraction KW - Hydrogen KW - Cracking KW - Offshore steel PY - 2022 AN - OPUS4-54576 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wandtke, Karsten A1 - Schröpfer, Dirk A1 - Kannengießer, Thomas A1 - Scharf-Wildenhain, Ronny A1 - Hälsig, Andre A1 - Kromm, Arne A1 - Hensel, J. T1 - Fertigungsbedingte Beanspruchungen und Kaltrisssicherheit in generativ gefertigten Bauteilen aus hochfesten Feinkornbaustählen N2 - Additive Fertigungsverfahren wie das Direct Energy Deposition-Arc (DED-Arc) oder Wire Arc Additive Manufacturing (WAAM) ermöglichen die effiziente Herstellung gewichtsoptimierter, endkonturnaher Bauteile im modernen Stahlbau. Steigerungen der Effizienz können durch den Einsatz hochfester Stähle erreicht werden, insbesondere durch Verringerung von Wandstärken und Bauteilgewicht sowie signifikante Einsparung von Kosten, Zeit und Ressourcen. DED-Arc Schweißzusatzwerkstoffe sind bereits auf dem Markt verfügbar, allerdings fehlen Richtlinien und quantitative Kenntnisse über die schweißbedingte Beanspruchung während der Fertigung und im Betrieb, welche den industriellen Einsatz stark limitieren. In einem gemeinsamen Projekt der BAM und der Technischen Universität Chemnitz wurden die wesentlichen Einflüsse und komplexen Wechselwirkungen von Werkstoff, Fertigungsverfahren, Konstruktion und Bearbeitungsschritten auf die Eigenspannungen untersucht. Ziel war es, den stahlverarbeitenden Anwendern, insbesondere KMU, eine risssichere und beanspruchungsgerechte Herstellung und Modifizierung von Bauteilen und Halbzeugen aus hochfesten Feinkornbaustahl unter Verwendung MSG-basierter generativer Verfahren zu ermöglichen. T2 - DVS Innovationstage 2024 CY - Düsseldorf, Germany DA - 10.04.2024 KW - Feinkornbaustähle KW - Additive Fertigung KW - Kaltrisssicherheit KW - Direct Energy Deposition-Arc (DED-Arc), Wire Arc Additive Manufacturing (WAAM) PY - 2024 AN - OPUS4-61934 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Thomas, Maximilian A1 - Liepold, Philipp A1 - Kannengießer, Thomas A1 - Schröpfer, Dirk T1 - Einfluss der Schweiß- und Prüfparameter bei der Heißrissbewertung hochfester Schweißzusatzwerkstoffe N2 - Die Heißrissneigung beim Schweißen kann mittels einer ganzen Reihe von Prüfverfahren ermittelt werden. Eine etablierte Methode ist die sogenannte Varestraint-Prüfung, welche auch an der Bundesanstalt für Materialforschung und -prüfung (BAM) als modifizierter Varestraint/Transvarestraint-Test (MVT) zum Einsatz kommt. Die Ergebnisse von Varestraint-Prüfungen hängen jedoch stets in unter-schiedlichem Maße von der individuellen Prüfmaschinenauslegung und den verwendeten Prüfparametern ab. Dies kann zu einer uneinheitlichen Bewertung des Rissverhaltens führen, wenn die Risslänge konventionell als Kriterium für die Rissneigung herangezogen wird. Scheinbare Abhängigkeiten von Prozessparametern erschweren dann die Interpretation der Ergebnisse. Eine neuartige Bewertungsmethodik entkoppelt den Maschineneinfluss vom Materialverhalten und verwendet die Dehnrate als Risskriterium. T2 - 5. Symposium Materialtechnik CY - Clausthal-Zellerfeld, Germany DA - 23.02.2023 KW - Heißrisse KW - Varestraint-Test PY - 2023 SN - 978-3-8440-9105-2 SN - 2364-0804 VL - 12 SP - 357 EP - 365 PB - Shaker CY - Düren AN - OPUS4-57993 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Eigenspannungen in mittels DED-Arc gefertigten Bauteilen aus hochfestem Stahl N2 - Der Vortrag gibt einen Überblick über die mittels XRD und Neutronenbeugung ermittelten Eigenspannungen in additiv gefertigten Bauteilen. Zusätzlich wird der Einfluss der Prozessparameter auf die Härte betrachtet. T2 - Frühjahrssitzung des Fachausschusses 13 Eigenspannungen der AWT CY - Berlin, Germany DA - 28.03.2023 KW - Eigenspannungen KW - DED-arc KW - Hochfester Stahl KW - Neutronenbeugung PY - 2023 AN - OPUS4-57289 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Hot Cracking Behavior of LTT Alloys under Variable Conditions in the Varestraint Test N2 - The use of Low Transformation Temperature (LTT) filler materials is an innovative way to reduce welding residual stresses. The generation of compressive residual stresses in the weld and heat-affected zone can lead to an improvement of the fatigue life of high-strength welds. However, high-alloy filler metals can be prone to solidification cracking. Two important LTT alloys were evaluated under variable welding and loading parameters using the Modified Varestraint/Transvarestraint (MVT) test. Initially conflicting results were interpreted using a newly developed image-based crack detection routine [1]. Based on the melt pool dimensions, the shape of the isotherms is reconstructed, and the theoretical crack growth along numerically determined crystallization paths is considered in relation to the cracks observed. Decreasing welding speeds with simultaneously higher heat input promote crack formation with increasing strain rate. T2 - International Joint Conference EMPOrIA 2023 CY - Aachen, Germany DA - 16.05.2023 KW - LTT KW - Solidification cracking KW - Varestraint test PY - 2023 AN - OPUS4-57546 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Rhode, Michael A1 - Kromm, Arne A1 - Mente, Tobias A1 - Czeskleba, Denis A1 - Brackrock, Daniel A1 - Kannengießer, Thomas T1 - Bauteilversuch zur Bewertung der wasserstoffunterstützten Rissanfälligkeit geschweißter, dickwandiger Offshore-Gründungsstrukturen N2 - Offshore-Windenergieanlagen erfordern Gründungskonzepte aus unterpulver-(UP-)geschweißten Dickblechen (bspw. der Güte S420ML). Während der Schweißfertigung kann eine zeitverzögerte wasserstoffunterstützte Kaltrissbildung auftreten, deren Bewertung aufgrund der Bauteilgröße von Offshore-Strukturen sehr komplex ist. Deswegen wurde eine bauteilähnliche Geometrie (Mock-Up) entwickelt, um reale Steifigkeitsverhältnisse auf den Labormaßstab zu übertragen. Zusätzliche Versteifungen simulieren die Wirkung einer Einspannung bzw. Schrumpfbehinderung der Schweißnaht. Über die Verwendung von Schweißpulvern mit definierter Feuchte wurden zudem ein Extremszenario der Wasserstoffaufnahme simuliert. Entsprechend der vorgegebenen Mindestwartezeit für die ZfP von bis zu 48 h wurde die Schweißnaht zerstörungsfrei mit Phased-Array-Ultraschall-Prüfung (PAUT) geprüft und die Eigenspannungen über Röntgendiffraktometrie (XRD) bestimmt. Zusätzlich wurde die Wasserstoffverteilung in der Schweißverbindung numerisch simuliert. Außer zulässigen Defekten (wie Poren), wurde keine verzögerte Kaltrissbildung in den Mock-Ups festgestellt, was auf hohe Rissbeständigkeit hindeutet. T2 - Tagung Werkstoffprüfung 2023 CY - Berlin, Germany DA - 23.11.2023 KW - Kaltrissbildung KW - Wasserstoff KW - Offshore KW - Schweißen KW - Bauteiltest PY - 2023 DO - https://doi.org/10.48447/WP-2023-219 SP - 316 EP - 321 CY - Berlin AN - OPUS4-58908 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Schroepfer, Dirk A1 - Kromm, Arne A1 - Kannengiesser, Thomas T1 - Stress-Optimised Welding Repair for High-Strength Offshore Steel Joints N2 - The successful energy transition in Germany will require offshore wind turbines with outputs >10 MW in the future. To achieve these high outputs, turbines far from the coast are required, featuring large subsea jacket structures (30 m up to 50 m) and tall towers (up to 200 m). High-strength steels with a yield strengths up to 500 MPa and wall thicknesses of up to 120 mm are increasingly being used for these structures. During manufacture, weld defects detected by non-destructive testing (NDT) require localized repair (gouging and rewelding). To date, there is a lack of repair concepts and information in standards and guidelines. Therefore, BAM initiated the FOSTA project P1629 (IGF 01IF22746N) to investigate the stress-optimized repair (local gouging and welding) of high-strength thick plate joints made of offshore grades in the yield strength range off 355 to 460 MPa and similar weld metal. This research aims to develop a stress-optimized repair concept for thick plate joints, using controlled high-performance GMAW processes and optimized, narrow gouging grooves. Thermal and mechanical gouging are performed, allowing the groove configuration to be modified. Modern welding processes provide deep root penetration and focused energy input capable of welding narrow seams. The aimed residual stress reduction can be attributed to the lower input of weld metal due to the changes in groove configuration and to the reduction in heat input per layer due to the controlled arc process. The experimental analyses take into account the interaction of process, material, and design-related influences on the formation of weld induced stresses. Concluding with recommendations for guidelines elaborated for steel-processing SMEs. T2 - MPA Stuttgart 2025 CY - Stuttgart, Germany DA - 06.10.2025 KW - Repair welding KW - Residual stress KW - High-strength steels KW - Gouging KW - Modern welding processes PY - 2025 AN - OPUS4-64347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Rhode, Michael A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Kadoke, Daniel A1 - Kruse, Julius T1 - Effect of Ti microalloying on the local strain behavior of cross-weld tensile samples determined by digital image correlation N2 - High-strength low-alloyed (HSLA) steels with yield strength / proof stress ≥ 600 MPa are the basis of modern light-weight steel constructions. Indeed, the economic and ecological benefits strongly depend on their processability in terms of welding. In this context, the use of highly productive welding processes and suitable welding consumables is of vital interest and requires a fundamental understanding of the microstructural changes in the HSLA steel and especially the heat-affected zone (HAZ) of the welded joint. Microalloying elements, such as Ti or Nb, are essential to achieve the desired mechanical properties. To analyse the weldability, three-layer welds were performed using gas metal arc welding (GMAW) and critical microstructures, such as areas of the HAZ that exhibit significant softening or hardening, were identified. The effect of the softened HAZ region on failure was evaluated using cross-weld tensile specimens. Digital image correlation (DIC) was used for in-situ monitoring of the development and accumulation of the local strains in different HAZ regions during tensile testing. Using a specially designed mirror system, the local strains of the microstructure zones on the top and bottom of the weld were recorded simultaneously. In addition, the analysis of the local deformation helps to understand the effects of the softened HAZ on the global strain, the reduction in area, the fracture position, and the overall fracture behavior. KW - High-strength structural steel KW - Microalloying influences KW - HAZ-softening KW - Digital Image Correlation KW - Constraint effect KW - Thermodynamic simulation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-643558 DO - https://doi.org/10.1007/s40194-025-02185-1 SP - 1 EP - 17 PB - Springer Nature AN - OPUS4-64355 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Uhlig, Marvin A1 - Schröder, Nina A1 - Höfer, Kevin A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Hensel, Jonas T1 - Schweißverfahrensqualifikation an Stumpfnahtverbindungen aus Altstahl- und Feinkornbaustahl N2 - Der Erhalt und die Ertüchtigung bestehender Stahltragwerke gewinnen im Bauwesen zunehmend an Bedeutung. Besonders betroffen sind Konstruktionen aus sogenannten Flussstählen, die im Zeitraum zwischen etwa 1880 und 1940, noch vor Einführung der ersten Stahlnorm DIN 488-1, in großem Umfang im Brücken-, Wasserbau- und Hochspannungsanlagenbau verwendet wurden. Diese Stähle wurden in historischen erstellungsverfahren wie dem Thomas-, Bessemer- oder Siemens-Martin-Verfahren erzeugt und weisen im Vergleich zu heutigen Baustählen eine deutlich größere Streuung in ihren chemischen und mechanischen Eigenschaften auf. Trotz ihres hohen Alters sind viele dieser Tragwerke nach wie vor im Betrieb und befinden sich am Rande ihrer statischen und funktionalen Anforderungen. Ihr Rückbau und Ersatz durch Neubauten sind jedoch oftmals mit erheblichem wirtschaftlichem, logistischem und ökologischem Aufwand verbunden. Daher rückt die Instandhaltung und Weiterverwendung solcher Altbauwerke verstärkt in den Fokus von Infrastrukturprogrammen, Sanierungsstrategien und besitzt eine große kulturelle Bedeutung. Im Rahmen der vorliegenden Untersuchung soll das Potenzial des MAG-Schweißens mit G 18 8 Mn Zusatzwerkstoff für Stumpfnahtverbindungen aus Flussstahl und Feinkornbaustahl qualifiziert werden. Ziel ist es, durch experimentelle und werkstofftechnische Analysen weitere Erkenntnisse über die Schweißbarkeit historischer Stähle zu gewinnen, Anwendungsempfehlungen für die Praxis abzuleiten und damit einen Beitrag zur sicheren und wirtschaftlichen Sanierung historischer Infrastrukturbauwerke zu leisten. T2 - DVS Congress 2025 CY - Essen, Germany DA - 16.09.2025 KW - Altstahl KW - MAG-Schweißen KW - Seigerungen KW - Instandsetzung KW - Feinkornbaustahl PY - 2025 SN - 978-3-96144-298-0 VL - 401 SP - 1 EP - 17 AN - OPUS4-64278 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - From the field to the lab and back: Evaluating the integrity of welded components using scaled experiments N2 - This contribution addresses the question of how the behaviour of complex parts or components in industrial practice can be simulated using simple welding experiments in the laboratory. It is demonstrated how so-called mock-ups can be utilised for this purpose. In particular, a test rig specially designed for scaled welding experiments is shown. It allows mechanical restraints and stiffnesses to be simulated, as well as typical welding process parameters and post weld heat treatments. Selected examples show how solidification crack growth during welding of high-strength steels can be quantified, under which conditions stress relaxation cracks occur during the heat treatment of heat-resistant steels, and how the integrity of pressurised hydrogen pipelines can be assessed during repair welding. T2 - 4th International Conference on Advanced Joining Processes 2025 CY - Coimbra, Portugal DA - 16.10.2025 KW - High strength steel KW - Stress relief cracking KW - Hydrogen PY - 2025 AN - OPUS4-64505 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reichel, Levin A1 - Schroepfer, Dirk A1 - Kromm, Arne A1 - Kannengiesser, Thomas T1 - Reduction of residual stress by narrowing the repair groove: Optimising repair welding with modern welding processes for high strength offshore steels N2 - The ongoing German energy transition will require offshore wind turbines with outputs of >10 MW in the future. Turbines with these high outputs must be located far from the coast, with up to 50 m large subsea jacket structures and tall towers. These structures are increasingly fabricated of high-strength steels with a yield strength up to 500 MPa and wall thicknesses of up to 120 mm. During production, weld defects identified through non-destructive testing (NDT) must be locally repaired by gouging and rewelding. Standards and guidelines lack sufficient concepts and information regarding such repair procedures. To address this gap, BAM launched the FOSTA project P1629 (IGF 01IF22746N) to explore stress-optimised repair concepts, specifically local gouging and welding, for high-strength thick plate joints made from offshore-grade steels with yield strengths between 355 MPa and 460 MPa, including matching weld metals. This research aims to develop a stress-optimised repair concept for thick plate joints, utilising controlled high-performance GMAW techniques and narrow gouging grooves. Both thermal and mechanical gouging methods are applied, enabling adjustments to the groove geometry. Modern welding processes offer deep root penetration and concentrated energy input, making them suitable for narrow seams. The intended reduction in residual stress results from the decreased weld metal volume, due to modified groove shapes and the lower heat input per layer achieved through controlled arc processes. Experimental investigations examine how process parameters, material properties, and design factors interact to influence the development of welding-induced stresses. The project concludes with practical recommendations for guidelines tailored to steel-processing SMEs. T2 - 4th International Conference on Advanced Joining Processes (AJP 2025) CY - Coimbra, Portugal DA - 16.10.2025 KW - Repair welding KW - Residual stress KW - Modern welding processes KW - High-strength offshore steel KW - Narrow groove PY - 2025 AN - OPUS4-64887 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stress Formation in selective laser melted parts of Alloy 718 N2 - Additive Manufacturing (AM) through the Selective Laser Melting (SLM) route offers ample scope for producing geometrically complex parts compared to the conventional subtractive manufacturing strategies. Nevertheless, the residual stresses which develop during the fabrication can limit application of the SLM components by reducing the load bearing capacity and by inducing unwanted distortion, depending on the boundary conditions specified during manufacturing. The present study aims at characterizing the residual stress states in the SLM parts using different diffraction methods. The material used is the nickel based superalloy Inconel 718. Microstructure as well as the surface and bulk residual stresses were characterized. For the residual stress analysis, X-ray, synchrotron and neutron diffraction methods were used. The measurements were performed at BAM, at the EDDI beamline of -BESSY II synchrotronand the E3 line -BER II neutron reactor- of the Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results reveal significant differences in the residual stress states for the different characterization techniques employed, which indicates the dependence of the residual state on the penetration depth in the sample. For the surface residual stresses, longitudinal and transverse stress components from X-ray and synchrotron agree well and the obtained values were around the yield strength of the material. Furthermore, synchrotron mapping disclosed gradients along the width and length of the sample for the longitudinal and transverse stress components. On the other hand, lower residual stresses were found in the bulk of the material measured using neutron diffraction. The longitudinal component was tensile and decreased towards the boundary of the sample. In contrast, the normal component was nearly constant and compressive in nature. The transversal component was almost negligible. The results indicate that a stress re-distribution takes place during the deposition of the consecutive layers. Further investigations are planned to study the phenomenon in detail. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Additive Manufacturing KW - Selective Laser Melting KW - Residual Stresses PY - 2018 AN - OPUS4-45979 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Cabeza, S. A1 - Nadammal, Naresh A1 - Bode, Johannes A1 - Kromm, Arne A1 - Haberland, C. A1 - Bruno, Giovanni ED - Richard, H. A. T1 - Der Einfluss der Hatch-Länge und der Probenabtrennung von der Bauplatte auf den Eigenspannungszustand in SLM-Bauteilen aus IN718 N2 - Die Schicht-für-Schicht additive Fertigung (AM) in Form des selektiven Laserschmelzens (SLM) bietet einerseits Vorteile bezüglich des Probendesigns, andererseits sind thermische Eigenspannungen (ES) aufgrund des hohen Temperaturgradienten unvermeidbar. Diese Eigenspannungen wurden in zwei SLM-gefertigten Proben aus IN718 zerstörungsfrei mit Neutronenstreuung hinsichtlich der folgenden zwei Einflüsse analysiert: der Einfluss der Hatch-Länge und das Abtrennen des Werkstücks von der Bauplatte. Begleitet wurden die Messungen der Eigenspannungen durch optische Mikroskopie und die taktile Vermessung der Oberfläche. Eine Korrelation zwischen den Eigenspannungen und der Hatch-Länge konnte beobachtet und erklärt werden. T2 - 2. Tagung des DVM-Arbeitskreises Additiv gefertigte Bauteile und Strukturen CY - Berlin, Germany DA - 09.11.2017 KW - IN718 KW - Additive Fertigung KW - Selektives Laserschmelzen KW - Eigenspannungen KW - Neutronenstreuung PY - 2017 SN - 2509-8772 VL - Bericht 402 SP - 137 EP - 146 PB - DVM CY - Berlin AN - OPUS4-42946 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Eigenspannungen in additiv gefertigten Bauteilen aus IN718 N2 - Additive Manufacturing (AM) by Selective Laser Melting (SLM) offers ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses which develop during the process can limit the application of SLM parts because they can reduce the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. This study aims at the characterization of residual stresses in SLM parts by using different measurement techniques. The material used is the nickel based super Alloy 718. The alloy is widely used in several applications in aerospace and chemical industries due to its superior corrosion and heat resistant properties. Microstructure as well as surface and bulk residual stresses were characterized. For residual stress analysis X-ray, synchrotron and neutron diffraction were applied. The measurements were performed at BAM, and at EDDI line -BESSY II synchrotron- and E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results show different residual stress states based on the different techniques, i.e. a dependence of the residual state on depth penetration in the sample. For the surface residual stresses, longitudinal and transversal stress components from both X-ray and synchrotron diffraction agree with the high tensile values around the yield limit. Furthermore, synchrotron mapping disclosed a gradient along width and length of the sample for both stress components. On the other hand, lower residual stresses are found in the bulk of the material. The longitudinal stress component is tensile and decreases towards the tip of the sample. In contrast, the normal component is almost constant and compressive in nature. The transversal component stays constant and is almost negligible. In summary, the samples of Alloy 718 manufactured by SLM process can show high tensile residual stresses in the surface as high as the yield strength of the wrought alloy. Residual stresses in the bulk show considerably lower stress values. This indicates that a stress re-distribution takes place during deposition of the SLM layers. Due to high residual stresses the dimensional stability of SLM parts can be affected as distortion can occur when removing the samples from the support structure. Future investigations are planned to study the phenomenon in detail. N2 - Die additive Fertigung (AM) mittels Selective Laser Melting (SLM) bietet großes Potential hinsichtlich der Herstellung geometrisch komplexer Bauteile im Vergleich zu herkömmlichen Fertigungsverfahren. Die sich während des Prozesses einstellenden Eigenspannungen können jedoch die Anwendung von SLM-Teilen einschränken, da sie die Tragfähigkeit reduzieren können und unerwünschten Verzug in Abhängigkeit der in der Fertigung festgelegten Randbedingungen verursachen können. Die vorliegende Arbeit beschäftigt sich mit der Charakterisierung von Eigenspannungen in SLM-Teilen unter Anwendung komplementärer Messtechniken. Das verwendete Material ist die Nickelbasis-Superlegierung 718. Die Legierung wird aufgrund ihrer überlegenen Korrosions- und Hochtemperaturbeständigkeit in vielen Anwendungen der Luft- und Raumfahrt- und der chemischen Industrie eingesetzt. Die Untersuchungen umfassen die Charakterisierung der Mikrostruktur sowie der Eigenspannungen in der Oberfläche als auch im Inneren der Bauteile. Für die Eigenspannungsanalyse wurden Röntgen-, Synchrotron- und Neutronenbeugung angewendet. Die Messungen wurden an der BAM, an der EDDI-Beamline bei BESSY II und an der E3-Beamline bei BER II des Helmholtz-Zentrums für Materialien und Energie (HZB) Berlin durchgeführt. Die Ergebnisse zeigen unterschiedliche Eigenspannungsverteilungen auf der Grundlage der verschiedenen Techniken, d. h. eine Abhängigkeit von der Eindringtiefe der jeweiligen Strahlung in die Probe. Für die oberflächennahen Eigenspannungen ergeben sich für die Längs- und Querspannungskomponenten sowohl für Röntgen- als auch für Synchrotronbeugung hohe Werte im Bereich der Fließgrenze. Darüber hinaus offenbarte die synchrotronbasierte Messung einen Gradienten entlang der Breite und Länge der Probe für beide Spannungskomponenten. Anderseits wurden geringere Eigenspannungen im Innern des Materials gefunden. Diese können richtungsabhängig auch im Druckbereich liegen. T2 - Fachausschuss 13 "Eigenspannungen" der AWT CY - Braunschweig, Germany DA - 10.10.2017 KW - Eigenspannungen KW - Additive Fertigung PY - 2017 AN - OPUS4-42516 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - In-situ-phase analysis using synchrotron radiation of low transformation temperature (LTT) welding material N2 - Cold cracking resistance is a relevant evaluation criterion for welded joints and affected by residual stresses which result from the welding procedure. Compressive residual stresses can thereby have a positive influence on preventing cracking. A unique possibility of generating compressive residual stresses already during the welding procedure is offered by the so-called Low Transformation Temperature (LTT) filler wires. Compared to conventional wires, these materials show decreased phase transformation temperatures which can work against the cooling-specific contraction. In consequence, distinct compressive residual stresses can be observed within the weld and adjacent areas. The strength of these fillers makes them potentially applicable to high-strength steel welding. Investigations were carried out to determine the phase transformation behaviour of different LTT-filler materials. Transformation temperatures were identified using Single Sensor Differential Thermal Analysis (SS-DTA). Additionally Synchrotron radiation was used to measure the transformation kinetics of all involved crystalline phases during heating and cooling of a simulated weld thermal cycle. KW - In-situ phase analysis KW - Energy dispersive diffraction KW - Phase transformation KW - Low Transformation Temperature filler wire PY - 2009 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-205922 DO - https://doi.org/10.1590/S0104-92242009000100010 SN - 0104-9224 SN - 1980-6973 VL - 14 IS - 1 SP - 82 EP - 88 PB - Associação Brasileira de Soldagem, ABS CY - Rio de Janeiro AN - OPUS4-20592 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Kromm, Arne T1 - Formation of welding residual stresses in low transformation temperature (LTT) materials N2 - For the safety and cost efficiency of welded high-strength steel structures, precise knowledge of the level and distribution of welding- and cooling-specific stresses and residual stresses is essential, since they exert a decisive influence on strength, crack resistance, and finally on the bearable service load. This paper presents innovative filler materials, of which the phase transformation temperature was deliberately adjusted via the chemical composition. The transformation behaviour of these martensitic Low Transformation Temperature (LTT-) filler materials shows direct effects on the local residual stresses in the weld and the HAZ. These effects can purposefully be exploited to counteract the thermally induced shrinkage of the material and to produce significant compressive residual stresses in the weld. Comparative welding experiments were carried out on 690 MPa high-strength base materials using various LTT-filler materials. High energy synchrotron radiation was used for residual stress measurement. Particularly the use of high energy synchrotron radiation makes it possible to detect the residual stress condition fast without destruction of material. Thereby, residual stress depth gradients can be determined simultaneously without removing material. In steel, gradients of up to 150 µm can be resolved in such a way. Furthermore, the application of high energy radiation permits determination of residual stresses of any available residual austenite contents. Results show significant dependence of transformation temperatures on the resulting residual stress level and distribution. KW - Phase specific residual stresses KW - Phase transformation KW - Low transformation temperature filler wire KW - Energy dispersive diffraction KW - High strength steel PY - 2009 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-205909 DO - https://doi.org/10.1590/S0104-92242009000100009 SN - 0104-9224 SN - 1980-6973 VL - 14 IS - 1 SP - 74 EP - 81 PB - Associação Brasileira de Soldagem, ABS CY - Rio de Janeiro AN - OPUS4-20590 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengiesser, Thomas T1 - Improvement of Fatigue Resistance through the Application of a Low-Transformation-Temperature Welding Consumable N2 - Low transformation temperature (LTT) welding consumables are an innovative approach to reduce tensile residual stress in weld seams and the surrounding heat affected zone (HAZ). The reduced tensile stress can lead to an improvement in fatigue strength of welded components. LTT alloys are characterized by a chemical composition which reduce the martensite start temperature (Ms) close to room temperature. This article focuses on a hybrid use of LTT filler metals, where the LTT filler is applied as an additional layer to conventional welds on fatigue-critical spots. Conventional gas metal arc welded longitudinal stiffeners are used as specimens. At the face ends of the stiffeners, a second LTT layer was added with various modifications in weld shapes. These different shapes were achieved by changing the welding parameters such as welding speed and offset to the first layer. These samples were used to analyze shape, dilution, resulting Ms, residual stress and fatigue strength. The dilatometer verified Ms and dilution did not change significant, although the area of the 2nd LTT weld seam was varying clear with each modification. However, the weld modification had a significant effect on the residual stress state and the fatigue strength. The X-ray determined residual stress in the HAZ became lower when the weld toe of the LTT layer was further away from the stiffener. All samples with LTT weld exhibit significantly higher fatigue strength values than conventionally single and double-layer welded samples. The lower the residual stress at weld toe, the higher the fatigue strength. The results show that on the one hand LTT filler metals increase the fatigue strength, and on the other hand the impact of LTT fillers materials is not restricted to the dilution and Ms, the shape of the weld seam must also be considered. T2 - 4th international Conference on Advanced Joining Processes AJP CY - Combria, Portugal DA - 16.10.2025 KW - Low transformation temperature (LTT) KW - Residual stress reduction KW - Fatigue strength KW - Longitudenal stiffener PY - 2025 AN - OPUS4-65090 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Die Hohlzugprobentechnik - Eine neue Methodik zur Untersuchung der Materialverträglichkeit unter Wasserstoffeinfluss N2 - Die schädigende Wirkung von Wasserstoff auf die mechanischen Eigenschaften von Stählen ist zwar bekannt, aber noch immer nicht ausreichend erforscht. Die schnelle und sichere Markteinführung von Wasserstofftechnologien macht es erforderlich, dieses Thema genauer zu untersuchen. Im Allgemeinen wird dies oft als Wasserstoffversprödung bezeichnet. Daher ist es wünschenswert, eine Prüfmethode zu entwickeln, die auf einfache Weise die Materialeigenschaften unter Wasserstoffatmosphäre ermitteln kann. Derzeit werden mechanische Prüfungen unter Wasserstoffatmosphäre in Autoklaven durchgeführt. Für diese Technik ist eine aufwendige Hardware erforderlich, daher sind die Prüfungen teuer und die Prüfkapazitäten nur in geringem Umfang verfügbar. Die hier vorgestellte Prüfmethode verspricht einen zukunftsweisenden Ansatz zur Reduzierung von Kosten und Bearbeitungszeiten durch die Verwendung von Hohlkörpern, d.h. die Probe selbst stellt den Autoklav dar. T2 - Sitzung des DIN-Gemeinschaftsarbeitsausschusses NA 092 00 05 GA, NAS/NMP: Zerstörende Prüfung von Schweißverbindungen CY - Berlin, Germany DA - 15.03.2023 KW - Prüfung KW - Wasserstoff KW - Probengeometrie KW - Hochdruck PY - 2023 AN - OPUS4-57168 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Saliwan Neumann, Romeo A1 - Farahbod, Lena A1 - Haberland, Christoph A1 - Portella, Pedro Dolabella T1 - Influence of support configurations on the characteristics of selective laser-melted Inconel 718 N2 - Samples fabricated using two different support configurations by following identical scan strategies during selective laser melting of superalloy Inconel 718 were characterized in this study. Characterization methods included optical microscopy, electron back-scattered diffraction and x-ray diffraction residual stress measurement. For the scan strategy considered, microstructure and residual stress development in the samples were influenced by the support structures. However, crystallographic texture intensity and the texture components formed within the core part of the samples were almost independent of the support. The formation of finer grains closer to the support as well as within the columnar grain boundaries resulted in randomization and texture intensity reduction by nearly half for the sample built on a lattice support. Heat transfer rates dictated by the support configurations in addition to the scan strategy influenced the microstructure and residual stress development in selective laser-melted Inconel 718 samples. KW - Additive manufacturing KW - Selective laser melting KW - Support configurations KW - Microstructure and texture KW - Residual stress PY - 2018 DO - https://doi.org/10.1007/s11837-017-2703-1 SN - 1047-4838 SN - 1543-1851 VL - 70 IS - 3 SP - 343 EP - 348 PB - Springer CY - USA AN - OPUS4-44175 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Kromm, Arne A1 - Kannengießer, Thomas ED - Carl E. Cross, ED - John C. Lippold, ED - Böllinghaus, Thomas ED - Herold, H. T1 - Influence of Local Weld Deformation on the Solidification Cracking Susceptibility of a Fully Austenitic Stainless Steel PY - 2008 SN - 978-3-540-78627-6 VL - II SP - 127 EP - 145 PB - Springer CY - Berlin AN - OPUS4-18642 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Nina A1 - Uhlig, Marvin A1 - Kromm, Arne A1 - Schröpfer, Dirk A1 - Höfer, Kevin A1 - Hensel, Jonas A1 - Kannengießer, Thomas T1 - Challenges in the evaluation of the weldability of old mild steels for future use N2 - For reasons of sustainability and cost efficiency, there is an increasing trend in the steel-processing industry to retrofit existing structures, avoiding costly shutdowns or dismantling. Although welding is a cost-effective joining method, it is rarely applied to old steels, whereas riveted or bolted connections are often uneconomical. Repair and refurbishment frequently require the replacement of damaged material or the creation of dissimilar old–new steel joints. Due to the varied manufacturing processes of historical steels, not all twentieth-century steels are inherently weldable, making an initial assessment of weldability essential. In this study, a historical non-deoxidized mild steel (produced by Siemens–Martin processing) originating from the construction of the Berlin Radio Tower (erected in 1926) was investigated using dilatometry to analyze its welding behavior. A database of welding CCT diagrams and HAZ simulations was established to support practice-oriented welding experiments, providing key insights into their weld-metallurgical behavior and weldability. Furthermore, initial welding trials were conducted, and the local residual stress states in dissimilar old–new steel joints were determined. These foundational investigations are critical for the development of innovative, load-adapted welding concepts for the repair and refurbishment of existing old-steel infrastructure in Germany. KW - Old mild steels KW - Repair welding KW - Weldability KW - Thermo-physical simulation KW - CCT diagrams PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654784 DO - https://doi.org/10.1007/s40194-026-02366-6 SN - 1878-6669 SP - 1 EP - 14 PB - Springer nature AN - OPUS4-65478 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hübner, Martin A1 - Dittmann, Florian A1 - Kromm, Arne A1 - Varfolomeev, Igor A1 - Kannengiesser, Thomas T1 - Enhancement of the fatigue strength by application of a low transformation temperature (LTT) welding consumable N2 - Low transformation temperature (LTT) welding consumables offer a possibility to enhance fatigue strength in welded components without post-treatment. By lowering the martensite start temperature (MS), the volume expansion during transformation near ambient temperature reduces welding related tensile residual stresses in fatigue-critical areas. To evaluate this effect, longitudinal stiffeners were used, a LTT and conventional filler serve as welding consumable, also high frequency mechanical impact (HFMI) treatment was carried out. Three single-pass and six additional-pass sample series were investigated on residual stress and fatigue strength. The additional welds were applied in fatigue crack critical areas with different weld shapes, achieved by varying welding parameters. Mechanical tests on reference samples evaluated the properties of the diluted LTT welds. Although reduced toughness was observed, no fatigue cracks occurred in LTT single-pass weld roots. The fatigue strength at two million cycles increased from 81 MPa to 121 MPa compared to conventional welds, while HFMI reached 146 MPa. With an additional LTT weld pass the results varied from 138 MPa to 196 MPa, depending to the shape and residual stress state. The results show that LTT fillers effectively enhance fatigue performance, and that weld geometry and parameter selection are as critical as the chemical composition for maximizing the LTT effect. CY - Genua, Italy DA - 22.06.2025 KW - Low transformation temperature (LTT) KW - Martensite start temperature KW - Residual stress KW - Longitudenal stiffener KW - Fatigue strength PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-654520 DO - https://doi.org/10.1007/s40194-026-02356-8 SP - 1 EP - 14 PB - Springer Nature AN - OPUS4-65452 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Dixneit, J. A1 - Gibmeier, J. A1 - Kromm, Arne A1 - Schubnell, J. A1 - Lang, F. A1 - Loebich, F. A1 - Carl, E.-R. A1 - Ya, W. T1 - Residual stress distribution of a large component manufactured by AM-DED-Arc from high-strength weld filler material X90 N2 - Currently, DED-Arc manufactured components are not covered by design guidelines, and design factors such as residual stress factors are not defined for such components. This hinders industrial use, especially for components with a remaining surface waviness required by industry. For the first time the stress state of a high-strength, low-alloy, large-scale DED-Arc component was characterised in the as-built state and after cutting off the component from the substrate plate. Complementary methods of residual stress analyses were applied to gain a holistic insight into the residual stress distributions of a thick-walled part. In the as-built state, direction-dependent and position-dependent tensile residual stresses were found for the component at the level of the yield strength of the part. The additive manufacturing strategy continuous spiral deposition has no significant influence on the residual stresses in bead threshold area compared to the residual stresses of the remaining component. For this case, bead threshold is no structural imperfection. By removing the part from the substrate plate, the residual stresses are significantly redistributed. Tensile residual stresses are then present at a moderate level. Compressive residual stresses were determined in the volume of the deposited material. The general consideration of ‘‘high’’ tensile residual stresses in such thick-walled components is rather conservative. Therefore, design guidelines should take the manufacturing condition into account. KW - AM-DED-Arc KW - Residual stress KW - High strength steel PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655239 DO - https://doi.org/10.1177/03093247251406876 SN - 2041-3130 SP - 1 EP - 18 PB - SAGE AN - OPUS4-65523 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Spranger, Felix A1 - Schirdewahn, S. A1 - Kromm, Arne A1 - Merklein, M. A1 - Hilgenberg, Kai T1 - On the influence of tib2, tic and tin hard particles on the microstructure of localized laser dispersed aisi d2 tool steel surfaces N2 - The control of friction and wear is a major concern in many industrial applications. A promising method for a tailored surface modification is the so-called laser implantation technique. This method combines surface texturing and material optimization in one processing step by a localized dispersing of hard ceramic particles using pulsed laser radiation. Wear resistant, protruding micrometric features (implants) with defined geometry can be created in deterministic pattern where needed on highly stressed surfaces, i.e. on forming or cutting tools. However, in order to maintain the implants over the tool’s lifetime, a suitable selection of hard ceramic particles is a prerequisite. They must provide a defect-free Metal Matrix Composite with a high share of homogeneously distributed particles and especially a high implant hardness. In this study TiN, TiC and TiB2 hard particles were compared as implant materials for the first time. By a systematic variation of the pulse power and pulse duration, their dispersing behavior and influence on the material properties of AISI D2 tool steel was investigated. Although all powder materials had grain sizes smaller than 10 µm, it was possible to disperse them by pulsed laser radiation and to obtain defect-free protruding implants. The highest share of dispersed particles (~64 %) was observed for TiB2. By scanning electron microscopy and energy dispersive X-ray spectroscopy, it was also shown that a significant share of the pre-placed particles was dissolved by the laser beam and precipitated as nanometer sized particles within the matrix during solidification. These in-situ formed particles have a decisive influence on the material properties. While the TiN and TiC implants have shown maximum hardness values of 750 HV1 and 850 HV1, the TiB2 implants have shown the highest hardness values with more than 1600 HV1. By X-ray diffraction, it was possible to ascribe the lower hardness values of TiC and TiN implants to high amounts of retained austenite in the metal matrix. By implanting TiB2, the formation of retained austenite was successfully suppressed due to the in-situ formation of TiC particles, which was proven by electron backscatter diffraction. In conclusion, all the implant materials are basically suitable for laser implantation on AISI D2 tool steel. However, TiB2 has shown the most promising results. T2 - 38th International Congress on Applications of Lasers & Electro-Optics CY - Orlando, FL, USA DA - 07.10.2019 KW - Laser implantation KW - Surface texturing KW - AISI D2 KW - TiB2 PY - 2019 SN - 978-1-940168-1-42 SP - 1 EP - 10 AN - OPUS4-49317 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Schaupp, Thomas A1 - Kannengießer, Thomas T1 - Welding stress control in high-strength steel components using adapted heat control concepts N2 - High-strength steels are increasingly applied in modern steel constructions to meet today’s lightweight requirements. Welding of these steels demands a profound knowledge of the interactions between the welding process, cooling conditions, heat input, and the resulting metallurgical occurrences in the weld and its vicinity. Additionally, welding stresses may be detrimental for the safety and performance of high-strength steel component welds during fabrication and service, especially due to the high yield ratio. For a development of strategies to adjust welding heat control, all these effects should be considered, to reach a complete exploitation of the high-strength steel potential. In recent researches at BAM, multilayer GMAW experiments were performed with high-strength steels, in which cooling conditions and resulting microstructure were analyzed for varied heat control parameters. The application of a unique 3d-operating testing facility and X-ray diffraction measurements allowed the analysis of local stresses in the weld while welding and cooling under component relevant shrinkage restraints. As a result, correlations between material behavior, welding, and cooling condition and the arising multi-axial stresses and forces were found. Based on this study, statements for the development of adapted heat control concepts were derived, which are presented by means of specific analysis examples. KW - Residual stresses KW - GMA welding KW - Restraint KW - High-strength steels KW - Process parameters PY - 2019 DO - https://doi.org/10.1007/s40194-018-00691-z SN - 0043-2288 VL - 63 IS - 3 SP - 647 EP - 661 PB - Springer AN - OPUS4-48006 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Bewertung konstruktiv bedingter Erstarrungsrisse beim Schweißen hochfester Feinkornbaustähle N2 - Die klassische Beurteilung der Heißrissneigung erfolgt bislang primär über das Prüfen der Schweißeignung des Werkstoffes. Die konstruktiven Bedingungen und bauteilspezifischen Beanspruchungszustände bleiben dabei meist unberücksichtigt. Die Vielzahl an Heißrisstests liefert dabei lediglich werkstoff-spezifische, empiri-sche Heißrissparameter, wie z. B. Gesamtrisslänge oder Gesamtrissanzahl. Eine Bauteilübertragbarkeit ist somit oftmals nicht gegeben, gerade wenn es sich um hochbeanspruchte Konstruktionsmerkmale des Leichtbaus handelt. Folglich sind mechanische Kenngrößen (risskritische Verformungen/Spannungen) zu identifizieren, die sicher und unter realitätsnahen Bedingungen erfasst werden können. Diese dienen als Transfergrößen, um die Heißrissanfälligkeit geschweißter Bauteile mit typischen Konstruktionsmerkmalen zu bewerten. T2 - Forschungsverbund HOCHFEST - Fosta e.V. CY - Dusseldorf, Germany DA - 25.09.2019 KW - Erstarrungsriss KW - Schweißen KW - Heißriss PY - 2019 AN - OPUS4-49268 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ferrari, Bruno A1 - Fantin, Andrea A1 - Said, D. A1 - Fitch, A. N. A1 - Suárez Ocano, Patricia A1 - Mishurova, Tatiana A1 - Roveda, Ilaria A1 - Kromm, Arne A1 - Darvishi Kamachali, Reza A1 - Bruno, Giovanni A1 - Evans, Alexander A1 - Requena, G. A1 - Agudo Jácome, Leonardo A1 - Serrano Munoz, Itziar T1 - The impact of scanning strategy on cell structures in PBF-LB/M/IN718: an in situ synchrotron x-ray diffraction study N2 - In additive manufacturing, any change of the process parameters, such as scanning strategy, directly affects the cooling rates, heat accumulation, and overall thermal history of the build. Consequently, parts built with different process parameters tend to have different levels of crystallographic texture, residual stress, and dislocation density. These features can influence the properties of the material and their development during post-processing operations. In this study, IN718 prisms were built by laser powder bed fusion (PBF-LB/M) using two different scanning strategies (continuous 67° rotations around the build direction, ROT, and alternating 0°/67° scans, ALT) to provide two different as-built conditions. In situ time-resolved synchrotron diffraction was performed during a solution heat treatment at 1027 °C for 1 h. Ex situ scanning electron microscopy was used to support and complement the in situ observations. An approach to quantify the effect of elemental microsegregation at the cell walls is developed based on the deconvolution of asymmetric γ-nickel matrix peaks. Following this approach, the scanning strategies are shown to affect the as-built fraction of cell walls in the material, resulting in a difference of approximately 5 %, in weight fraction, between ROT and ALT (19 % vs. 24 %, respectively). This microsegregation was observed to be rapidly homogenized during the heating ramp, and no significant changes to the peak shape in the γ peaks occurred during the isothermal part of the heat treatment, regardless of the scanning strategy. KW - Additive manufacturing KW - Inconel 718 KW - Synchrotron x-ray diffraction KW - Heat treatment KW - Laser powder bed fusion KW - Cellular microstructure PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-650958 DO - https://doi.org/10.1016/j.jmrt.2025.11.214 SN - 2238-7854 VL - 41 SP - 593 EP - 608 PB - Elsevier B.V. AN - OPUS4-65095 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Kromm, Arne A1 - Seyfert, Christoph A1 - Farahbod, Lena A1 - Haberland, Christoph A1 - Schneider, Judith Ann A1 - Portella, Pedro Dolabella A1 - Bruno, Giovanni T1 - Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718 N2 - In the present study, samples fabricated by varying the deposition hatch length during selective laser melting of nickel based superalloy Inconel 718 were investigated. Microstructure and texture of these samples was characterized using scanning electron microscopy, combined with electron back-scattered diffraction, and residual stress assessment, using neutron diffraction method. Textured columnar grains oriented along the sample building direction were observed in the shorter hatch length processed sample. A ten-fold increase in the hatch length reduced the texture intensity by a factor of two attributed to the formation of finer grains in the longer hatch length sample. Larger gradients of transverse residual stress in the longer hatch length sample were also observed. Along the build direction, compressive stresses in the shorter hatch length and negligible stresses for the longer hatch length specimen were observed. Changes to the temperature gradient (G) in response to the hatch length variation, influenced the G to growth rate (R) ratio and the product G × R, in agreement with the microstructures and textures formed. For the residual stress development, geometry of the part also played an important role. In summary, tailored isotropy could be induced in Inconel 718 by a careful selection of parameters during selective laser melting. KW - Additive manufacturing KW - Nickel-based superalloy KW - Microstructure and texture KW - Residual stress KW - Electron back-scattered diffraction KW - Neutron diffraction PY - 2017 UR - http://www.sciencedirect.com/science/article/pii/S0264127517308018 DO - https://doi.org/10.1016/j.matdes.2017.08.049 SN - 0264-1275 VL - 134 SP - 139 EP - 150 PB - Elsevier CY - Oxford, UK AN - OPUS4-41606 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Jakob A1 - Evans, Alexander A1 - Luzin, V. A1 - Abreu Faria, G. A1 - Degener, Sebastian A1 - Polatidis, E. A1 - Čapek, J. A1 - Kromm, Arne A1 - Dovzhenko, G. A1 - Bruno, Giovanni T1 - Texture-based residual stress analysis of laser powder bed fused Inconel 718 parts N2 - Although layer-based additive manufacturing methods such as laser powder bed fusion (PBF-LB) offer an immense geometrical freedom in design, they are typically subject to a build-up of internal stress (i.e. thermal stress) during manufacturing. As a consequence, significant residual stress (RS) is retained in the final part as a footprint of these internal stresses. Furthermore, localized melting and solidification inherently induce columnar-type grain growth accompanied by crystallographic texture. Although diffraction-based methods are commonly used to determine the RS distribution in PBF-LB parts, such features pose metrological challenges in their application. In theory, preferred grain orientation invalidates the hypothesis of isotropic material behavior underlying the common methods to determine RS. In this work, more refined methods are employed to determine RS in PBF-LB/M/IN718 prisms, based on crystallographic texture data. In fact, the employment of direction-dependent elastic constants (i.e. stress factors) for the calculation of RS results in insignificant differences from conventional approaches based on the hypothesis of isotropic mechanical properties. It can be concluded that this result is directly linked to the fact that the {311} lattice planes typically used for RS analysis in nickel-based alloys have high multiplicity and less strong texture intensities compared with other lattice planes. It is also found that the length of the laser scan vectors determines the surface RS distribution in prisms prior to their removal from the baseplate. On removal from the baseplate the surface RS considerably relaxes and/or redistributes; a combination of the geometry and the scanning strategy dictates the sub-surface RS distribution. KW - Additive manufacturing KW - Electron backscattered diffraction KW - Principal stress KW - Residual stress PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-578331 DO - https://doi.org/10.1107/S1600576723004855 SN - 1600-5767 VL - 56 IS - Pt 4 SP - 1076 EP - 1090 AN - OPUS4-57833 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Mohr, Gunther A1 - Altenburg, Simon A1 - Evans, Alexander A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Pirling, T. A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Triaxial Residual Stress in Laser Powder Bed Fused 316L: Effects of Interlayer Time and Scanning Velocity N2 - The triaxial distribution of the residual stress in laser powder bed fused austenitic steel 316L was determined by X-ray and neutron diffraction. The residual stress analysis results were linked to the thermal history of the specimens, which were manufactured with varying inter-layer-times and scanning velocities. A clear link between the in-process temperature of the specimens and the residual stress was found, based on in-situ monitoring data. KW - Stainless Steel KW - AGIL KW - Residual Stress KW - X-ray and Neutron Diffraction KW - Additive Manufacturing PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542620 DO - https://doi.org/10.1002/adem.202101330 SP - 1 EP - 13 PB - Wiley-VCH GmbH AN - OPUS4-54262 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Cabeza, S. A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Thiede, Tobias A1 - Bruno, Giovanni T1 - Residual Stresses in Selective Laser Melted Samples of a Nickel Based Superalloy N2 - Additive Manufacturing (AM) through the Selective Laser Melting (SLM) route offers ample scope for producing geometrically complex parts compared to the conventional subtractive manufacturing strategies. Nevertheless, the residual stresses which develop during the fabrication can limit application of the SLM components by reducing the load bearing capacity and by inducing unwanted distortion, depending on the boundary conditions specified during manufacturing. The present study aims at characterizing the residual stress states in the SLM parts using different diffraction methods. The material used is the nickel based superalloy Inconel 718. Microstructure as well as the surface and bulk residual stresses were characterized. For the residual stress analysis, X-ray, synchrotron and neutron diffraction methods were used. The measurements were performed at BAM, at the EDDI beamline of -BESSY II synchrotronand the E3 line -BER II neutron reactor- of the Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results reveal significant differences in the residual stress states for the different characterization techniques employed, which indicates the dependence of the residual state on the penetration depth in the sample. For the surface residual stresses, longitudinal and transverse stress components from X-ray and synchrotron agree well and the obtained values were around the yield strength of the material. Furthermore, synchrotron mapping disclosed gradients along the width and length of the sample for the longitudinal and transverse stress components. On the other hand, lower residual stresses were found in the bulk of the material measured using neutron diffraction. The longitudinal component was tensile and decreased towards the boundary of the sample. In contrast, the normal component was nearly constant and compressive in nature. The transversal component was almost negligible. The results indicate that a stress re-distribution takes place during the deposition of the consecutive layers. Further investigations are planned to study the phenomenon in detail. T2 - European Conference on Residual Stresses - ECRS10 CY - Leuven, Belgium DA - 11.09.2018 KW - Additive Manufacturing KW - Selective Laser Melting KW - Residual Stresses PY - 2018 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-459818 SN - 978-1-94529-189-0 SN - 978-1-94529-188-3 DO - https://doi.org/10.21741/9781945291890-41 SN - 2474-395X SN - 2474-3941 VL - 6 SP - 259 EP - 264 PB - Materials Research Forum LLC CY - Millersville, PA 17551, USA AN - OPUS4-45981 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Sprengel, Maximilian A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Nolze, Gert A1 - Saliwan Neumann, Romeo A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - The residual stress in as‑built Laser Powder Bed Fusion IN718 alloy as a consequence of the scanning strategy induced microstructure N2 - The effect of two types of scanning strategies on the grain structure and build-up of Residual Stress (RS) has been investigated in an as-built IN718 alloy produced by Laser Powder Bed Fusion (LPBF). The RS state has been investigated by X-ray diffraction techniques. The microstructural characterization was performed principally by Electron Backscatter Diffraction (EBSD), where the application of a post-measurement refinement technique enables small misorientations (< 2°) to be resolved. Kernel average misorientation (KAM) distributions indicate that preferably oriented columnar grains contain higher levels of misorientation, when compared to elongated grains with lower texture. The KAM distributions combined with X-ray diffraction stress maps infer that the increased misorientation is induced via plastic deformation driven by the thermal stresses, acting to self-relieve stress. The possibility of obtaining lower RS states in the build direction as a consequence of the influence of the microstructure should be considered when envisaging scanning strategies aimed at the mitigation of RS. KW - Additive manufacturing KW - LPBF KW - Residual stress KW - Inconel 718 KW - Kernel average misorientation KW - Texture PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-511769 DO - https://doi.org/10.1038/s41598-020-71112-9 VL - 10 IS - 1 SP - 14645 AN - OPUS4-51176 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Dixneit, Jonny A1 - Lausch, Thomas A1 - Hannemann, Andreas A1 - Kannengießer, Thomas T1 - Von der Anwendung ins Prüflabor: Maßstabsgetreues Bewerten von Spannungen in geschweißten Bauteilen N2 - Eigenspannungen sind von zentraler Bedeutung für die Performance geschweißter Bauteile. Die Bewertung schweißbedingter Beanspruchungen im Labormaßstab ist oft nicht zielführend. Reale Bauteilschweißungen weisen geometrisch und konstruktiv bedingt meist divergente Wärmeableitungs- und Einspannbedingungen auf. Dadurch lassen sich häufig nur eingeschränkt Aussagen über Eigenspannungshöhen, -verteilungen und die wesentlichen Einflussfaktoren treffen. Dies führt oftmals zur eher konservativen Konstruktionsauslegung und damit zu einer geringerenRessourcen- und Energieeffizienz. Dieser Beitrag widmet sich den Bestrebungen, reale Randbedingungen beim Bauteilschweißen in das Labor zu übertragen. Es werden die Möglichkeiten eines speziell für diesen Zweck an der BAM entwickelten Prüfsystems mit einer maximalen Tragkraft von 2 MN aufgezeigt. Durch die konstruktive Gestaltung der Anlage lassen sich in Schweißversuchen schweißbedingte Beanspruchungen nachbilden und die komplexen Einflüsse und Wechselwirkungen durch Schweißprozess, Bauteilgeometrie und -konstruktion sowie durch die eingesetzten Grund- und Zusatzwerkstoffe quantifizieren. Darüber hinaus können mittels Röntgenbeugung die resultierenden lokalen Eigenspannungen präzise und mit hoher Ortsauflösung bestimmt werden. Anhand von Beispielen wird die Nachbildung realer Produktionsbedingungen im Labor erörtert und gezeigt, wie die Spannungen beim Schweißen hochfester Baustähle von konstruktiven, werkstoff- und prozessseitigen Randbedingungen abhängen. So wurde geklärt, wie erhöhte Arbeitstemperaturen zum signifikanten Anstieg der Beanspruchungen führen. T2 - DVS Congress 2019 Große Schweißtechnische Tagung CY - Rostock, Germany DA - 16.09.2019 KW - Schweißen KW - Eigenspannungen KW - Bauteilprüfung PY - 2019 SN - 978-3-96144-066-5 VL - 355 SP - 280 EP - 286 PB - DVS Media GmbH CY - Düsseldorf AN - OPUS4-50279 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Einfluss schweißbedingter Spannungen auf die Relaxationsrissbildung bei der Wärmebehandlung warmfester 13CrMoV-Stähle N2 - Wirtschaftliche und ökologische Aspekte führten in den letzten Jahren zu deutlich gesteigerten Anforderungen an die Effizienz und die Flexibilität petrochemischer Anlagen. Die heutzutage geforderten Prozesstemperaturen und -drücke lassen sich nur durch den Einsatz neuer warmfester Stahlgüten erreichen. Der mit Vanadium modifizierte Stahl 13CrMoV9-10 weist eine bessere Kriech- und Druckwasserstoffbeständigkeit auf und wird seit Mitte der 90er Jahre im petrochemischen Reaktorbau eingesetzt. Aufgrund der niedrigen Zähigkeit und hohen Festigkeit des Schweißgutes im geschweißten, nicht spannungsarm geglühten Zustand sowie einer erhöhten Sensitivität gegenüber Spannungsrelaxationsrissen bedarf dieser Stahl allerdings einer äußerst sorgfältigen schweißtechnischen Verarbeitung. Bisherige Untersuchungen zur Rissentstehung in warmfesten Stählen konzentrierten sich vorrangig auf thermische und metallurgische Einflussfaktoren, bieten jedoch nur wenige Erkenntnisse zum Einfluss des Schweißprozesses auf die Rissbildung beim Spannungsarmglühen unter Berücksichtigung realitätsnaher Fertigungsbedingungen. Im ersten Teil wurde zunächst der Einfluss der Wärmeführung auf die mechanischen Eigenschaften anhand von frei schrumpfenden Laborproben untersucht. Während sich die Wärmeführung wesentlich auf die Schweißnahtstruktur auswirkte, war ein signifikanter Effekt auf die mechanischen Eigenschaften nicht nachweisbar. Auch traten infolge der Wärmenachbehandlung der frei schrumpfend geschweißten Proben keine Spannungsrelaxationsrisse auf. Der zweite Teil umfasste die realitätsnahe Abbildung der Fertigungsbedingungen im petrochemischen Reaktorbau. Zu diesem Zweck wurden die konstruktiven Randbedingungen während des Vorwärmens, Schweißens, des Wasserstoffarmglühens und der abschließenden Wärmenachbehandlung realitätsnah in einer speziellen 3-D-Prüfanlage zur Simulation von Bauteilschweißungen abgebildet. Unter konstruktiver Schrumpfbehinderung gelang der Nachweis der unterschiedlichen Wirkung von Vorwärm- / Zwischenlagentemperatur und Streckenenergie auf die resultierenden Kräfte, Momente und Spannungen. Die Gesamtreaktionsspannung nach dem Schweißen wurde innerhalb des untersuchten Parameterfeldes maßgeblich durch die Streckenenergie beeinflusst. Ein möglichst geringer Gesamtwärmeeintrag hat die niedrigste Bauteilbeanspruchung zur Folge. Während der Wärmenachbehandlung kam es in allen Versuchen zu Spannungsrelaxationsrissen. Deren kumulierte Länge korrelierte mit den ermittelten schweißbedingten Reaktionsspannungen. Die Detektion der Risse während der Wärmenachbehandlung im Bauteilversuch erfolgte erstmalig in-situ mittels Schallemissionsanalyse. Die Rissinitiierung fand nachweislich im Temperaturbereich von 300 °C bis 500 °C statt. Die Reaktionsspannungen nach der Wärmenachbehandlung lagen unabhängig von der Ausgangsbelastung auf einem vergleichbaren Niveau. Die Zähigkeit der Schweißverbindung nahm klar gegenüber den frei schrumpfend geschweißten Proben ab. Mittels REM- und TEM-Analysen an vergleichbaren belasteten und unbelasteten Proben wurde eine beschleunigte Alterung, durch das frühzeitige Ausscheiden von Sonderkarbiden während der Wärmenachbehandlung unter definierter Einspannung (d. h. unter Belastung), nachgewiesen. Die verstärkte Korngrenzensegregation korrelierte mit der signifikanten Abnahme der Kerbschlagarbeit der unter Einspannung geschweißten Proben. T2 - Fachausschuss 13 "Eigenspannungen" der AWT CY - Ilmenau, Germany DA - 07.05.2019 KW - Schweißen KW - Warmfester Stahl KW - Spannungsrelaxationsrisse PY - 2019 AN - OPUS4-47977 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Schwingfestigkeitsverbesserung hochfester Schweißverbindungen mit Hilfe neuartiger LTT-Zusatzwerkstoffe N2 - Die Verwendung von LTT-Zusatzwerkstoffen stellt einen alternativen Ansatz zu den sonst üblichen Verfahren der Schweißnahtnachbehandlung zur Schwingfestigkeitserhöhung geschweißter Stahlkonstruktionen dar. Der wesentliche Wirkmechanismus beruht auf der Beeinflussung des Eigenspannungszustands durch die niedrige Martensitstarttemperatur bereits während des Schweißens. Dadurch werden die Druckeigenspannungen aus der behinderten Volumenausdehnung infolge Phasenumwandlung voll wirksam. Weiter weist die Schweißnaht eine hohe Härte auf, die die Schwingrissbildung verzögern kann, allerdings auch zu einer niedrigen Kerbschlagarbeit führt. Im ersten Teil dieses Beitrages werden grundlegende Untersuchungen zur schweißtechnischen Verarbeitung eines LTT-Zusatzwerkstoffes präsentiert. Dies beinhaltet zunächst die Sicherstellung der Schweißbarkeit sowie die Charakterisierung der Schweißgefüge und deren Härte mit dem Ziel, reproduzierbare Verbindungseigenschaften für die nachfolgende Schwingfestigkeitsprüfung herzustellen. Der zweite Teil des Beitrages beschäftigt sich mit den dazugehörigen Schwingfestigkeitsuntersuchungen an den Stählen S355J2 und S960Q unter Verwendung konventioneller Zusatzwerkstoffe im Vergleich zum LTT-Zusatz. Das verwendete Schweißdetail ist eine Verbindungsschweißung am Stumpfstoß unter Variation der Schweißnahtausführung (DY-Naht und V-Naht). Weitergehend wird eine bauteilähnliche Probe (die Längssteife) untersucht, bei der der LTT-Zusatzwerkstoff als zusätzliche Schweißlage aufgebracht wurde. Neben der Schwingfestigkeit werden die Schweißnähte hinsichtlich der Eigenspannungen, der Eigenspannungsstabilität im Schwingversuch sowie metallografisch charakterisiert. Die Ergebnisse zeigen, dass LTT-Zusatzwerkstoffe unter Einhaltung wesentlicher Konstruktionsrichtlinien zu einem deutlichen Anstieg der Schwingfestigkeit führen. Dadurch kann das Leichtbaupotential hochfester Stahlgüten genutzt werden. T2 - Sitzung des NA 092-00-05 GA „Gemeinschaftsarbeitsausschuss NAS/NMP: Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1)“ CY - Magdeburg, Germany DA - 13.03.2019 KW - Eigenspannungen KW - Schwingfestigkeit KW - Schweißen PY - 2019 AN - OPUS4-47590 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Effect of weld penetration on hydrogen-assisted cracking in welding of high-strength structural steels T1 - Einfluss von Schweißprozess und Einbrandverhalten auf die Kaltrissbildung hochfester Feinkornbaustähle N2 - In the present study, the susceptibility to HAC of the HSLA steel S960QL with same type of filler material was investigated. For that purpose, both Conv. A and Mod. SA were used with same weld heat input at different deposition rates. For assessment of the HAC susceptibility, the externally loaded Implant-test [ ] was used. Both conducted test series with Conv. A and Mod. SA showed similar crack critical stress of about 280 MPa. Below this value, no delayed fracture appeared. The welds with Mod. SA showed higher hydrogen concentrations. The fracture occurred in the heat-affected zone (HAZ) or in the weld metal (WM). But in all specimens, cracks initiated at the notch root of the spiral notch of the implants within the coarse-grained HAZ. However, the test series with Mod. SA showed a significant extension of the time-to-failure of several hours compared to tests carried out with Conv. A, see Fig. 1a. The reason is the deeper weld penetration in case of Mod. SA (Fig. 1b and Fig. 1c), which causes longer diffusion path for hydrogen. The fracture topography of the ruptured implant specimens with Conv. A was typical ductile in specimen center and quasi-cleavage like at the edge of the specimens. When using Mod. SA, the topography changed to primarily quasi-cleavage fracture topography with shares of intergranular fracture and secondary crack appearance. T2 - Sitzung des NA 092-00-05 GA „Gemeinschaftsarbeitsausschuss NAS/NMP: Zerstörende Prüfung von Schweißverbindungen (DVS AG Q 4/Q 4.1)“ CY - Magdeburg, Germany DA - 13.03.2019 KW - Hydrogen-assisted cracking KW - Welding KW - High-strength steel PY - 2019 AN - OPUS4-47591 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Influence of welding stresses on relaxation cracking during heat treatment of a creep-resistant 13CrMoV steel N2 - Over the past years economic and environmental considerations have led to a markedly increased demand for efficiency and flexibility in petrochemical plants. The operational temperatures and pressures required today can only be achieved by using new creep-resistant grades of steel. The modified 13CrMoV9-10 vanadium steel shows a good resistance against creep and compressed hydrogen and has been in use for the construction of petrochemical reactors since the mid-1990s. Nevertheless, processing of this type of steel requires extreme care during the welding procedure. This is due to its low toughness and high strength in the welded state when not post weld heat treated combined with increased susceptibility to cracking during stress relaxation. Previous research into crack formation in creep-resistant steels has largely focused on thermal and metallurgical factors; however, little knowledge has been gathered regarding the influence of the welding procedure on crack formation during post weld heat treatment considering real-life manufacturing conditions. The influence of heat control on the mechanical properties has been investigated by simulating the welding and subsequent post weld heat treatment operations during the construction of petrochemical reactors using a special 3-D testing facility on the laboratory scale. This work is subdivided in two parts. In part I of this study the stresses resulting from preheating, welding, dehydrogenation heat treatment and the final post weld heat treatment were analyzed during experiments under varied heat control. In all experiments stress relief cracks formed during post weld heat treatment could be observed. The total crack lengths correlated with the welding induced stresses. Part II of this work is dedicated to the characterization of the cracks and the microstructure. The application of a special acoustic emission analysis indicated that the cracks formed in a temperature range between 300 °C and 500 °C during the post weld heat treatment. In comparison to small scale specimens welded without additional shrinkage restraint, the toughness of the restrained welds was significantly decreased. SEM and TEM analyses of all samples revealed accelerated aging due to early precipitation of special carbides during post weld heat treatment under component relevant restraint. T2 - IIW Annual Assembly CY - Bratislava, Slovakia DA - 08.07.2019 KW - Welding KW - Creep-resistant steel KW - Post weld heat treatment KW - Stress relief cracking PY - 2019 AN - OPUS4-48580 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Online-Observation of Martensite Formation by combined use of Synchrotron Diffraction and Dilatometry N2 - Welding residual stress engineering by means of an adjusted martensite phase transformation would be highly attractive as detrimental tensile residual stresses may be prevented already during welding without time and cost intensive post processing. The present study shows a synchrotron diffraction analysis of a martensitic steel subjected to thermo-mechanical load cycles. Experiments were conducted regarding the microstructural strain response during the austenite to martensite transformation. The strains are a function of the temperature and the specific loads applied during cooling. The relation between the transformation plasticity of the material, the amount of martensite formed and the arising strains can thus be assessed. The lattice plane specific strains were compared to experimental findings from (macro) dilatation tests. It is shown that the microscopic material behavior differs remarkably from the one observed on the macroscopic scale, what leads to characteristic residual stresses in the material. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Martensite KW - Synchrotron KW - Dilatometry KW - Residual stress KW - Phase transformation PY - 2019 SP - 83 EP - 84 PB - SEIEI Printing Co., Ltd CY - Osaka, Japan AN - OPUS4-49770 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Online-Observation of Martensite Formation by combined use of Synchrotron Diffraction and Dilatometry N2 - Welding residual stress engineering by means of an adjusted martensite phase transformation would be highly attractive as detrimental tensile residual stresses may be prevented already during welding without time and cost intensive post processing. The present study shows a synchrotron diffraction analysis of a martensitic steel subjected to thermo-mechanical load cycles. Experiments were conducted regarding the microstructural strain response during the austenite to martensite transformation. The strains are a function of the temperature and the specific loads applied during cooling. The relation between the transformation plasticity of the material, the amount of martensite formed and the arising strains can thus be assessed. The lattice plane specific strains were compared to experimental findings from (macro) dilatation tests. It is shown that the microscopic material behavior differs remarkably from the one observed on the macroscopic scale, what leads to characteristic residual stresses in the material. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Martensite KW - Synchrotron KW - Dilatometry KW - Residual stress KW - Phase transformation PY - 2019 AN - OPUS4-49768 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Lausch, Thomas A1 - Schröpfer, Dirk A1 - Hannemann, Andreas T1 - In-situ Observation of Stress Evolution and Cracking during High Strength Steel Welding N2 - Residual stresses are crucial when assessing the performance of welded components. The present work deals with the possibilities of transferring the real-life boundary conditions of welding, which influence the residual stress, into the laboratory. The possibilities of a test system with a load capacity of 2 MN specifically developed for online monitoring of stress formation and cracking are shown. Due to the structural design, global process, geometry and material-dependent stresses are induced, which can be quantified in-situ during welding and post weld heat treatment. Examples are presented how the conditions to be found during production are simulated in the laboratory. It is shown how welding residual stresses in high-strength steels are affected by the heat control. Elevated working temperatures significantly increase the tensile residual stresses in the heat affected zone (HAZ). The effect of mechanical stresses resulting from welding on stress relief cracking is demonstrated by the example of a creep resistant steel. Reheat cracks were monitored online during post weld heat treatment. T2 - Visual-JW 2019 & WSE 2019 The 5th International Symposium on Visualization in Joining & Welding Science through Advanced Measurements and Simulation & The 8th International Conference of Welding Science and Engineering CY - Osaka, Japan DA - 21.11.2019 KW - Residual stress KW - Restraint KW - Welding KW - Large-scale test KW - Reheat cracking PY - 2019 SP - 83 EP - 84 PB - SEIEI Printing Co., Ltd CY - Osaka, Japan AN - OPUS4-49773 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Trofimov, Anton A1 - Apel, D. A1 - Ulbricht, Alexander A1 - Kromm, Arne A1 - Hesse, René A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - On the interplay of microstructure and residual stress in LPBF IN718 N2 - The relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90° XY-scan, and 67° Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the nearsurface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen Dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuß model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kröner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys. KW - L-PBF IN718 material KW - Effect of scanning strategies KW - Near-surface X-ray diffraction KW - Residual stress in AM KW - Distortion upon baseplate removal PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-519460 DO - https://doi.org/10.1007/s10853-020-05553-y SN - 0022-2461 VL - 56 IS - 9 SP - 5845 EP - 5867 PB - Springer AN - OPUS4-51946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Ulbricht, Alexander A1 - Fritsch, Tobias A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Hofmann, M. A1 - Wimpory, R. C. A1 - Evans, Alexander A1 - Bruno, Giovanni T1 - Scanning Manufacturing Parameters Determining the Residual Stress State in LPBF IN718 Small Parts N2 - The influence of scan strategy on the residual stress (RS) state of an as-built IN718 alloy produced by means of laser powder bed fusion (LPBF) is investigated. Two scan vector rotations (90°-alternation and 67°-rotation), each produced following two different scan vector lengths (long and short), are used to manufacture four rectangular prisms. Neutron diffraction (ND) and laboratory X-ray diffraction (XRD) techniques are used to map the bulk and surface RS state, respectively. The distortion induced upon removal from the baseplate is measured via profilometry. XRD measurements show that the two long scan vector strategies lead to higher RS when compared with the equivalent short scan vector strategies. Also, the 67°-rotation strategies generate lower RS than their 90°-alternation counterparts. Due to the lack of reliable stress-free d0 references, the ND results are analyzed using von Mises stress. In general, ND results show significant RS spatial non-uniformity. A comparison between ND and distortion results indicates that the RS component parallel to the building direction (Z-axis) has a predominant role in the Z-displacement. The use of a stress balance scheme allows to discuss the d0 variability along the length of the specimens, as well as examine the absolute RS state. KW - As-built LPBF IN718 alloy KW - Scan strategy influence KW - Neutron diffraction KW - Residual stress state KW - Stress balance condition KW - Distortion PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-526360 DO - https://doi.org/10.1002/adem.202100158 VL - 23 IS - 7 SP - 158 PB - Wiley AN - OPUS4-52636 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Evans, Alexander A1 - Mishurova, Tatiana A1 - Sprengel, Maximilian A1 - Pirling, T. A1 - Kromm, Arne A1 - Bruno, Giovanni T1 - The importance of subsurface residual stress in laser powder bed fusion IN718 N2 - The residual stress (RS) in laser powder bed fusion (LPBF) IN718 alloy samples produced using a 67°-rotation scan strategy is investigated via laboratory X-ray diffraction (XRD) and neutron diffraction (ND). The location dependence of the strain-free (d₀) lattice spacing in ND is evaluated using a grid array of coupons extracted from the far-edge of the investigated specimen. No compositional spatial variation is observed in the grid array. The calculated RS fields show considerable non-uniformity, significant stress gradients in the region from 0.6 to 2 mm below the surface, as well as subsurface maxima that cannot be accounted for via XRD. It is concluded that failure to determine such maxima would hamper a quantitative determination of RS fields by means of the stress balance method. KW - Laser powder bed fusion KW - Neutron and X-ray diffraction KW - Residual stress analysis KW - Strain-free lattice references KW - Stress balance PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-532707 DO - https://doi.org/10.1002/adem.202100895 SN - 1615-7508 SN - 1527-2648 VL - 24 IS - 6 SP - 1 EP - 7 PB - Wiley-VCH CY - Weinheim AN - OPUS4-53270 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Mishurova, Tatiana A1 - Thiede, Tobias A1 - Cabeza, Sandra A1 - Bruno, Giovanni A1 - Kromm, Arne A1 - Nadammal, Naresh T1 - The influence of the support structure on residual stress and distortion in SLM Inconel 718 parts N2 - The effect of support structure and of removal from the base plate on the residual stress state in Selective Laser Melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after the cutting from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support stress redistribution took place after removal of the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress relieving heat treatments are still needed. T2 - User Meeting HZB 2018 CY - Berlin, Germany DA - 14.12.2017 KW - Additive manufacturing KW - Selective laser melting KW - Residual stress KW - Synchrotron X-ray diffraction PY - 2017 AN - OPUS4-43460 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni A1 - Mishurova, Tatiana A1 - Serrano-Munoz, Itziar A1 - Ulbricht, Alexander A1 - Fritsch, Tobias A1 - Sprengel, Maximilian A1 - Evans, Alexander A1 - Kromm, Arne A1 - Madia, Mauro ED - Bruno, Giovanni T1 - A Critical Discussion on the Diffraction-Based Experimental Determination of Residual Stress in AM Parts N2 - As opposed to reviewing results on experimental determination of residual stress by diffraction, this paper discusses the open issues when dealing with residual stress determination in additive manufactured parts, in particular those manufactured with laser powder bed fusion techniques. Three points are addressed in detail: (a) the proper determination of the strain-free reference d0, (b) the problem of the determination of the principal axes, and (c) the use of the correct diffraction elastic constants. It is shown that all methods to determine the strain-free reference d0 suffer from caveats, and care must be taken in evaluating the most suitable for the problem being tackled. In addition, it is shown that, in some systems, the principal axes do correspond to the geometrical axes of the specimen, but this needs to be systematically checked, especially in the case of uni- or bidirectional hatching strategies. Finally, the need to experimentally determine the proper diffraction elastic constants is underlined, especially in the case of strongly textured specimens, which again depends on the deposition strategy. T2 - ASTM ICAM 2020 – ASTM International Conference on Additive Manufacturing CY - Online meeting DA - 16.11.2020 KW - Additive Manufacturing KW - Diffraction KW - Residual Stress PY - 2020 DO - https://doi.org/10.1520/STP163120190148 VL - STP1631 SP - 122 EP - 138 PB - ASTM International CY - USA AN - OPUS4-51347 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sprengel, Maximilian A1 - Ulbricht, Alexander A1 - Evans, Alexander A1 - Kromm, Arne A1 - Sommer, Konstantin A1 - Werner, Tiago A1 - Kelleher, J. A1 - Bruno, Giovanni A1 - Kannengießer, Thomas T1 - Towards the optimization of post-laser powder bed fusion stress-relieve treatments of stainless steel 316L N2 - This study reports on the stress relaxation potential of stress-relieving heat treatments for laser powder bed fused 316L. The residual stress is monitored non-destructively using neutron diffraction before and after the heat treatment. Moreover, the evolution of the microstructure is analysed using scanning electron microscopy. The results show, that a strong relaxation of the residual stress is obtained when applying a heat treatment temperature at 900°C. However, the loss of the cellular substructure needs to be considered when applying this heat treatment strategy. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-536045 DO - https://doi.org/10.1007/s11661-021-06472-6 SN - 1543-1940 VL - 52 IS - 12 SP - 5342 EP - 5356 PB - Springer CY - Boston AN - OPUS4-53604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nadammal, Naresh A1 - Mishurova, Tatiana A1 - Fritsch, Tobias A1 - Serrano-Munoz, Itziar A1 - Kromm, Arne A1 - Haberland, C. A1 - Portella, Pedro Dolabella A1 - Bruno, Giovanni T1 - Critical role of scan strategies on the development of microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing N2 - Laser based powder bed fusion additive manufacturing offers the flexibility to incorporate standard and userdefined scan strategies in a layer or in between the layers for the customized fabrication of metallic components. In the present study, four different scan strategies and their impact on the development of microstructure, texture, and residual stresses in laser powder bed fusion additive manufacturing of a nickel-based superalloy Inconel 718 was investigated. Light microscopy, scanning electron microscopy combined with electron backscatter diffraction, and neutron diffraction were used as the characterization tools. Strong textures with epitaxially grown columnar grains were observed along the build direction for the two individual scan strategies. Patterns depicting the respective scan strategies were visible in the build plane, which dictated the microstructure development in the other planes. An alternating strategy combining the individual strategies in the successive layers and a 67◦ rotational strategy weakened the texture by forming finer microstructural features. Von Mises equivalent stress plots revealed lower stress values and gradients, which translates as lower distortions for the alternating and rotational strategies. Overall results confirmed the scope for manipulating the microstructure, texture, and residual stresses during laser powder bed fusion additive manufacturing by effectively controlling the scan strategies. KW - Additive manufacturing KW - Laser powder bed fusion KW - Nickel-based superalloys KW - Scan strategies KW - Residual stresses KW - Microstructure and texture PY - 2021 DO - https://doi.org/10.1016/j.addma.2020.101792 VL - 38 SP - 1792 PB - Elsevier B.V. AN - OPUS4-51944 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Thiede, Tobias A1 - Cabeza, Sandra A1 - Mishurova, Tatiana A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, C. A1 - Bruno, Giovanni T1 - An assessment of bulk residual stress in selective laser melted Inconel 718 N2 - Additive Manufacturing (AM) of metals has become industrially viable for a large variety of applications, including aerospace, automotive and medicine. Powder bed techniques such as Selective Laser Melting (SLM) based on layer-by-layer deposition and laser melt enable numerous degrees of freedom for the geometrical design. Developing during the manufacturing process, residual stresses may limit the application of SLM parts by reducing the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. The residual stress distribution in the bulk of IN718 elongated prisms produced by SLM was studied non-destructively by means of neutron diffraction. The samples with different scanning strategies, i.e. hatching length, were measured in as-build condition (on a build plate) and after removal from the build plate. The absolute values of all stress components decreased after removal from the build plate. Together with surface scan utilizing a coordinate-measuring machine (CMM), it is possible to link the stress release to the sample distortion. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component depending on the thermal gradient in the respective direction. T2 - ECNDT 2018 CY - Göteborg, Sweden DA - 11.06.2018 KW - Residual stress KW - Selective laser melting KW - Neutron diffraction KW - IN718 PY - 2018 UR - http://cdn.ecndt2018.com/wp-content/uploads/2018/05/ecndt-0315-2018-File001.pdf SP - 1 AN - OPUS4-45325 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mishurova, Tatiana A1 - Cabeza, Sandra A1 - Thiede, Tobias A1 - Nadammal, Naresh A1 - Kromm, Arne A1 - Klaus, Manuela A1 - Genzel, Christoph A1 - Haberland, Christoph A1 - Bruno, Giovanni T1 - The influence of the support structure on residual stress and distortion in SLM Inconel 718 parts N2 - The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed. KW - Additive manufacturing KW - SLM KW - Residual stress KW - Synchrotron X-ray diffraction KW - IN718 PY - 2018 DO - https://doi.org/10.1007/s11661-018-4653-9 SN - 1073-5623 VL - 49A IS - 7 SP - 3038 EP - 3046 PB - Springer Sciences & Business Media CY - New York, NY AN - OPUS4-45100 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bruno, Giovanni A1 - Thiede, Tobias A1 - Mishurova, Tatiana A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Bode, Johannes A1 - Cabeza, Sandra T1 - Influence of deposition hatch length on residual stress in selective laser melted Inconel 718 N2 - The present study aims to evaluate the bulk residual stresses in SLM parts by using neutron diffraction measurements performed at E3 line -BER II neutron reactor- of Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. Together with microstructure characterization and distortion measurements, it is possible to describe the stress state throughout the whole sample. The sample was measured in as-build condition (on a build plate) and after releasing from the build plate. The used material is the nickel based superalloy 718. This alloy is widely used in aerospace and chemical industries due to its superior corrosion and heat resistant properties. Obtained results indicated different residual stress states for each of the transversal, longitudinal and normal component. The normal and transversal component exhibits a rather compressive behavior while the longitudinal was tensile in the center part of the sample and became compressive towards the tip. As expected, the absolute values of all stress components decreased after releasing the sample from the building plate. A surface scan utilizing a coordinate-measuring machine (CMM) allowed us to present top surface distortion before and after releasing. The top surface showed a distortion around ±80µm after releasing. Microstructure evolution in the scanning-building cross-section is largely dominated by columnar grains. In addition, many small random orientated grains are prominent in the regions of a laser overlap during SLM. In summary, for the sample of superalloy 718 manufactured by SLM, a small distortion occurred when removing the sample from the build plate whereby the residual stress state decreases. Moreover, the observed columnar grains in the building direction could give a reason for the lowest stress values in that normal direction. However, the most important parameter controlling the residual stresses is the temperature gradient. Hence, future investigations are planned for a different scan strategy to distribute the laser impact in a more homogenous manner. T2 - WAM2018 CY - Grenoble, France DA - 09.04.2018 KW - Additive manufacturing KW - SLM KW - Residual stress KW - In718 PY - 2018 AN - OPUS4-44694 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stress formation in selective laser melted parts of Alloy 718 N2 - Additive manufacturing (AM) by selective laser melting (SLM) offers ample scope for producing geometrically complex parts as compared to the traditional subtractive manufacturing strategies. However, the residual stresses which develop during the process can limit the application of SLM parts because they can reduce the load bearing capacity as well as induce unwanted distortion depending on the boundary conditions specified in manufacturing. This study aims at the characterization of residual stresses in SLM parts by using different measurement techniques. The material used is the nickel based super Alloy 718. Microstructure as well as surface and bulk residual stresses were characterised. For residual stress analysis X-ray, synchrotron and neutron diffraction were applied. The results show different residual stress states dependent on the penetration depth in the sample offered by the different measurement techniques. Samples of Alloy 718 manufactured by SLM process can show high tensile residual stresses in the surface as high as the yield strength of the wrought alloy. Residual stresses in the bulk show considerably lower stress values. T2 - 1st International Congress on Welding, Additive Manufacturing and associated non-destructive testing - ICWAM CY - Metz, France DA - 17.05.2017 KW - Additive Manufacturing KW - Selective Laser Melting KW - Residual stresses PY - 2017 AN - OPUS4-40345 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schröder, Jakob A1 - Evans, Alexander A1 - Mishurova, Tatiana A1 - Ulbricht, Alexander A1 - Sprengel, Maximilian A1 - Serrano-Munoz, Itziar A1 - Fritsch, Tobias A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Bruno, Giovanni T1 - Diffraction-Based Residual Stress Characterization in Laser Additive Manufacturing of Metals N2 - Laser-based additive manufacturing methods allow the production of complex metal structures within a single manufacturing step. However, the localized heat input and the layer-wise manufacturing manner give rise to large thermal gradients. Therefore, large internal stress (IS) during the process (and consequently residual stress (RS) at the end of production) is generated within the parts. This IS or RS can either lead to distortion or cracking during fabrication or in-service part failure, respectively. With this in view, the knowledge on the magnitude and spatial distribution of RS is important to develop strategies for its mitigation. Specifically, diffraction-based methods allow the spatial resolved determination of RS in a non-destructive fashion. In this review, common diffraction-based methods to determine RS in laser-based additive manufactured parts are presented. In fact, the unique microstructures and textures associated to laser-based additive manufacturing processes pose metrological challenges. Based on the literature review, it is recommended to (a) use mechanically relaxed samples measured in several orientations as appropriate strain-free lattice spacing, instead of powder, (b) consider that an appropriate grain-interaction model to calculate diffraction-elastic constants is both material- and texture-dependent and may differ from the conventionally manufactured variant. Further metrological challenges are critically reviewed and future demands in this research field are discussed. KW - Laser-based additive manufacturing KW - Residual stress analysis KW - X-ray and neutron diffraction KW - Diffraction-elastic constants KW - Strain-free lattice spacing PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538054 DO - https://doi.org/10.3390/met11111830 VL - 11 IS - 11 SP - 1830 PB - MPDI CY - Basel AN - OPUS4-53805 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Serrano-Munoz, Itziar A1 - Pfretzschner, Beate A1 - Kromm, Arne A1 - Nadammal, Naresh A1 - Kardjilov, N. A1 - Markötter, Henning A1 - Neuwirth, T. A1 - Schulz, M. A1 - Griesche, Axel T1 - High-resolution Bragg-edge neutron radiography detects grain morphology in PBF-LB/M IN718 N2 - One of the main advantages of metal additive manufacturing (MAM) techniques is their ability to produce components with site-specific microstructural features. Nevertheless, microstructural defects and lack of repeatability are still major concerns in MAM. In this study, a laser powder bed fusion (PBF-LB/M) IN718 material, produced using two different scan length vectors, is investigated using Bragg-edge neutron 2D imaging (BENI) combined with electron backscatter diffraction (EBSD) analysis. BENI is able to detect, on a macroscopic scale, process-induced changes in texture in a large field of view covering the entire sample (20×80 mm2). In addition, high-resolution BENI (HR-BENI), with a pixel size of 12.8 µm, provides a micro-scale examination of the local variations of texture and grain morphology, otherwise undistinguishable using the standard resolution. As such, HR-BENI offers a straightforward and detailed way of screening the integrity of MAM parts at cm-length scales. KW - Bragg-edge neutron 2D imaging (BENI) KW - Metal additive manufacturing (MAM) KW - IN718 PBF-LB/M KW - Crystallographic texture control KW - Electron backscatter diffraction (EBSD) PY - 2023 DO - https://doi.org/10.1016/j.mtla.2023.101827 SN - 2589-1529 VL - 30 SP - 1 EP - 6 PB - Elsevier CY - Amsterdam AN - OPUS4-57819 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thiede, Tobias A1 - Cabeza, S. A1 - Mishurova, Tatiana A1 - Nadammal, N. A1 - Kromm, Arne A1 - Bode, Johannes A1 - Haberland, C. A1 - Bruno, Giovanni T1 - Residual stress in selective laser melted Inconel 718: Influence of the removal from base plate and deposition hatch length N2 - The residual stress distribution in IN718 elongated prisms produced by Selective Laser Melting was studied by means of neutron (bulk) and laboratory X-ray (surface) diffraction. Two deposition hatch lengths were considered. A horizontal plane near the top surface (perpendicular to the building direction) and a vertical plane near the lateral surface (parallel to the building direction) were investigated. Samples both in as-built (AB) condition and removed (RE) from the base plate were characterized. While surface stress fields seem constant for AB condition, X-ray diffraction shows stress gradients along the hatch direction in the RE condition. The stress profiles correlate with the distortion maps obtained by tactile probe measurements. Neutron diffraction shows bulk stress gradients for all principal components along the main sample directions. We correlate the observed stress patterns with the hatch length, i.e. with its effect on temperature gradients and heat flow. The bulk stress gradients partially disappear after removal from the baseplate. KW - Residual stress KW - Additive manufacturing KW - Neutron diffraction KW - Selective laser melting KW - Laboratory X-ray diffraction KW - Coordinate measurement machine KW - IN718 PY - 2018 DO - https://doi.org/10.1520/MPC20170119 SN - 2379-1365 VL - 7 IS - 4 SP - 717 EP - 735 PB - ASTM International CY - USA, West Conshohocken AN - OPUS4-46673 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Residual stress formation in selective laser melted parts of alloy 718 N2 - Additive Manufacturing (AM) through the Selective Laser Melting (SLM) route offers ample scope for producing geometrically complex parts compared to the conventional subtractive manufacturing strategies. Nevertheless, the residual stresses which develop during the fabrication can limit application of the SLM components by reducing the load bearing capacity and by inducing unwanted distortion, depending on the boundary conditions specified during manufacturing. The present study aims at characterizing the residual stress states in the SLM parts using different diffraction methods. The material used is the nickel based superalloy Inconel 718. Microstructure as well as the surface and bulk residual stresses were characterized. For the residual stress analysis, X-ray, synchrotron and neutron diffraction methods were used. The measurements were performed at BAM, at the EDDI beamline of -BESSY II synchrotron- and the E3 line -BER II neutron reactor- of the Helmholtz-Zentrum für Materialien und Energie (HZB) Berlin. The results reveal significant differences in the residual stress states for the different characterization techniques employed, which indicates a dependence of the residual state on the penetration depth in the sample. For the surface residual stresses, longitudinal and transverse stress components from both X-ray and synchrotron agree well and the obtained values were around the yield strength of the material. Furthermore, synchrotron mapping disclosed gradients along the width and length of the sample for the longitudinal and transverse stress components. On the other hand, lower residual stresses were found in the bulk of the material measured using neutron diffraction. The longitudinal component was tensile and decreased towards the boundary of the sample. In contrast, the normal component was nearly constant and compressive in nature. The transversal component was almost negligible. The results indicate that a stress re-distribution takes place during the deposition of the consecutive layers. Further investigations are planned to study the phenomenon in detail. T2 - Forschungsseminar OvGU Magdeburg CY - Magdeburg, Germany DA - 15.11.2018 KW - Additive Manufacturing KW - Selective Laser Melting KW - Residual Stresses PY - 2018 AN - OPUS4-46876 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Launert, B. A1 - Rhode, Michael A1 - Kromm, Arne A1 - Pasternak, H. A1 - Kannengießer, Thomas ED - Olden, T.-M. ED - Muransky, O. ED - Edwards, L. T1 - Residual stress influence on the flexural buckling of welded I-girders N2 - The nonlinear analysis became a common tool to precisely assess the load-bearing behavior of steel beam and column members. The failure level is significantly influenced by different types of imperfections, among geometric also structural imperfections (residual stresses). Here are still gaps in the knowledge. Nowadays, 3-D welding simulation developed to a level where it could provide reliable estimation of weld-induced distortion and residual stresses. Nevertheless, modelling and computational effort are still in a less practicable range. In this study a simplified procedure to implement residual welding stresses in continuous large scale members is proposed and the influence on the ultimate limit state of slender members in compression is evaluated for two common structural steel grades. The results showed significant improvements in the utilization of load bearing capacity compared with simplified design methods. The comparatively general approach in this study offers potential for future optimization. T2 - ICRS 2016 - 10th International Conference on Residual Stresses CY - Sydney, Australia DA - 03.07.2016 KW - Stability Design KW - Finit Element Method KW - 2-D Welding Simulation KW - Inherent Strain KW - Plasticity-based Analysis PY - 2016 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-389210 SN - 978-1-94529117-3 SN - 978-1-94529117-6 DO - https://doi.org/10.21741/9781945291173-19 SN - 2474-395X VL - 2 SP - 109 EP - 114 PB - Materials Research Forum LLC CY - Millersville (PA), USA AN - OPUS4-38921 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne A1 - Rhode, Michael A1 - Launert, B. A1 - Dixneit, Jonny A1 - Kannengießer, Thomas A1 - Pasternak, H. ED - Olden, T.-M. ED - Muransky, O. ED - Edwards, L. T1 - Combining sectioning method and X-ray diffraction for evaluation of residual stresses in welded high strength steel components N2 - Residual stresses and distortions in welded I-girders for steel construction are relevant when evaluating the stability of steel beams and column members. The application of high strength steels allows smaller wall thicknesses compared to conventional steels. Therefore, the risk of buckling has to be considered carefully. Due to the lack of knowledge concerning the residual stresses present after welding in high strength steel components conservative assumptions of their level and distribution is typically applied. In this study I-girders made of steels showing strengths of 355 MPa and 690 MPa were welded with varying heat input. Due to the dimension of the I-girders and the complex geometry the accessibility for residual stress measurement using X-ray diffraction was limited. Therefore, saw cutting accompanied by strain gauge measurement has been used to produce smaller sections appropriate to apply X-ray diffraction. The stress relaxation measured by strain gauges has been added to residual stresses determined by X-ray diffraction to obtain the original stress level and distribution before sectioning. The combination of both techniques can produce robust residual stress values. From practical point of view afford for strain gauge application can be limited to a number of measuring positions solely to record the global amount of stress relaxation. X-ray diffraction can be applied after sectioning to determine the residual stresses with sufficient spatial resolution. T2 - ICRS 2016 - 10th International Conference on Residual Stresses CY - Sydney, Australia DA - 03.07.2016 KW - Welding KW - Residual Stress KW - Sectioning Method KW - X-Ray Diffraction KW - Component Testing PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-389206 SN - 978-1-94529117-3 SN - 978-1-94529117-6 DO - https://doi.org/10.21741/9781945291173-28 SN - 2474-395X VL - 2 SP - 163 EP - 168 PB - Materials Research Forum LLC CY - Millersville (PA), USA AN - OPUS4-38920 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kromm, Arne T1 - Werkstoffsichere Dickblechschweißung und KI N2 - Der Vortrag zeigt, welche Herausforderungen beim Schweißen sogenannter Dickblechverbindungen bestehen und welche Strategien zur Lösung genutzt werden können. Ansätze zur Fehlerprävention werden vorgestellt. Es wird dargestellt, wie KI-basierte Methoden die Fehlererkennung erleichtern. Letztlich werden Potentiale zur effizienten Fehlerbeseitigung aufgezeigt und der Anwendernutzen herausgestellt. T2 - Mitgliederversammlung der Forschungsvereinigung Stahlanwendung e. V. CY - Essen, Germany DA - 17.12.2025 KW - UP-Schweißen KW - Eigenspannungen KW - Künstliche Intelligenz KW - Reparatur PY - 2025 AN - OPUS4-65210 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Kromm, Arne T1 - Umwandlungsverhalten und Eigenspannungen beim Schweißen neuartiger LTT-Zusatzwerkstoffe N2 - Die Erkenntnis, dass die Phasenumwandlung bei der Schweißeigenspannungsentstehung hochfester Stähle eine bedeutende Rolle spielt, gibt es bereits seit langer Zeit. Bisher existierten jedoch keine Ansätze, diesen Effekt praktisch zur Schweißeigen- spannungskontrolle zu nutzen. Neuartige Low Transformation Temperature (LTT) Legierungen bieten aufgrund ihrer charakteristischen chemischen Zusammensetzung die Möglichkeit, hochfeste Stähle auf deren Festigkeitsniveau zu fügen. Die martensitische Phasenumwandlung soll zudem eine gezielte Einstellung der Schweißeigenspannungen erlauben. Die im Schrifttum vorliegenden Untersuchungen zu diesem Thema sind zwar zahlreich, bieten jedoch nur wenige Erkenntnisse zur Wechselwirkung zwischen der Phasenumwandlung und den resultierenden Schweißeigenspannungen. Zur Klärung dieser Fragestellung wurde basierend auf Literaturauswertungen eine Matrix von LTT-Legierungen verwirklicht, welche hinsichtlich des Gefüges, der mechanischen Eigenschaften und der Umwandlungstemperaturen charakterisiert wurden. Weiterhin konnten im Rahmen dieser Arbeit erstmals In-situ-Beugungsexperimente während des Schweißens unter Anwendung energiedispersiver Methoden realisiert werden. Die Neukonzeption und Verwirklichung einer Schweißvorrichtung speziell für den Einsatz an Synchrotronstrahllinien ermöglichte die bislang einzigartige In-situ-Analyse der Umwandlungsvorgänge während des Schweißens mit LTT-Legierungen. Im Zuge dieser Experimente konnte neben den im Schweißgut vorherrschenden Umwandlungstemperaturen zusätzlich die Umwandlungskinetik dieser Legierungen ermittelt werden. Die Auswirkungen des Umwandlungsverhaltens wurden anhand der Eigenspannungsverteilungen in der Oberfläche variierender Probengeometrien analysiert. Die Ergebnisse verdeutlichen einerseits, dass die mittels der LTT-Legierungen angestrebte Eigenspannungskontrolle tatsächlich möglich ist. Dies zeigt sich insbesondere dann, wenn eine weitgehend freie Schrumpfung der Naht vorliegt. Mit zunehmender Schrumpfbehinderung ergibt sich jedoch eine Verschiebung des Eigenspannungsniveaus in den Zugbereich. Dies ist bei den hier betrachteten Legierungen vornehmlich in Nahtquerrichtung ausgeprägt. Dagegen ist das Eigenspannungsniveau in Nahtlängsrichtung nahezu unabhängig von den Schrumpfbedingungen. Anhand von Eigenspannungstiefengradienten ließ sich feststellen, dass sich die zusätzliche Schrumpfbehinderung in einer Parallelverschiebung des Eigenspannungsniveaus im Schweißgut äußert. Die Anwendung energiedispersiver Beugungsmethoden erlaubte zudem erstmals die Eigenspannungsermittlung in der parallel zum Martensit vorliegenden austenitischen Phase der LTT-Legierungen. Ergebnisse, die unter Laborbedingungen gewonnen werden, bedürfen zumeist der Überprüfung unter realen Fertigungsbedingungen. Zu diesem Zweck wurde ein Bauteilschweißversuch in einer speziellen Großprüfanalage durchgeführt. Unter konstruktiver Schrumpfbehinderung gelang es, die lastabbauende Wirkung eines spezifischen LTT-Schweißzusatzes anhand einer ausgeprägten Spannungsreduktion während des Schweißens zu belegen. Insgesamt wurde der Nachweis erbracht, dass das Konzept der Low Transformation Temperature (LTT) Legierungen zielführend ist und die nachgewiesene Austenit-Martensitumwandlung einen signifikanten Effekt auf das Eigenspannungsniveau ausübt. N2 - It has long been recognized that phase transformation plays a prominent part in the Evolution of welding residual stresses in high-strength steel. But thus far, no approaches have been available to practically utilize this effect for welding residual stress control. Innovative Low Transformation Temperature (LTT) alloys featuring a characteristic chemical composition open up the possibility for joining high strength steels on their own strength level. Furthermore, martensitic phase transformation is supposed to permit deliberate adjustment of the welding residual stresses. Even though numerous investigations can be found in the literature on this issue, they provide only little insight into the interaction between Phase transformation and resulting welding residual stresses. In order to clarify the problem presented, a matrix of LTT alloys was defined based on evaluated literature. The alloys were characterized with respect to their microstructure, mechanical properties and transformation temperature. Furthermore, it was possible within the scope of this study to realize in-situ experiments during welding using energy-dispersive diffraction methods. The new design and implementation of a welding setup specifically for use at synchrotron beamlines enabled the in-situ diffraction analysis of Transformation processes. In the course of these experiments it could be managed to determine the Transformation temperatures prevailing in the LTT weld metal. In addition the Transformation kinetics of these alloys could be analyzed. The effects of the transformation behavior were analyzed based on the residual stress distributions at the surface of varying specimen geometries. The results illustrate on the one hand that the desired residual stress control by using LTT alloys is actually feasible. This is particularly found in cases with largely free shrinkage of the weld. With increasing shrinkage restraint, however, a shift of the residual stress level into the area of tension is seen to occur. This is observed for the considered alloys to be particularly pronounced in transverse direction of the weld. By contrast, the residual stress level in longitudinal weld direction is nearly independent of the shrinkage conditions. With the help of residual stress depth gradients it could be established that the additional shrinkage restraint manifests itself in a parallel shift of the residual stress level in the weld metal. Application of energy-dispersive diffraction methods additionally allowed it for the first time to determine residual stresses in the austenitic phase of the LTT alloy which is present parallel to martensite. Results gained under laboratory conditions mostly need to be verified under real fabrication conditions. For this purpose, a component weld test was performed in a special large-scale testing facility. Under structural shrinkage restraint, the load relieving effect of a specific LTT welding filler material could be proven by means of a pronounced stress reduction during welding. Overall, evidence was furnished that the concept of Low Transformation Temperature (LTT) alloys is successful and that the proven austenite-martensite transformation exerts a significant effect on the residual stress level. T3 - BAM Dissertationsreihe - 72 KW - residual stresses KW - Synchrotron diffraction KW - phase transformation KW - martensite KW - Eigenspannungen KW - LTT-Zusatzwerkstoff KW - Martensit KW - Phasenumwandlung KW - Synchrotronbeugung KW - LTT filler material PY - 2011 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-861 SN - 978-3-9813853-9-7 SN - 1613-4249 VL - 72 SP - 1 EP - 223 PB - Bundesanstalt für Materialforschung und -prüfung (BAM) CY - Berlin AN - OPUS4-86 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -