TY - JOUR A1 - Schaupp, Thomas A1 - Schröpfer, Dirk A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Welding residual stress distribution of quenched and tempered and thermo-mechanically hot rolled high strength steels N2 - Beside quenched and tempered (QT) high strength steels advanced technologies in steel manufacturing provide steels produced by the thermo-mechanical controlled process (TMCP) with yield strength of 960 MPa. These steels differ in the carbon and micro-alloying element content. With variation of heat control TIG-welded dummy seams on both steel types were performed. Analyses concerning microstructure and residual stress evolution due to welding showed typical stress distributions according to common concepts. Yet, the TMCP-steel shows higher residual stresses than the QT-steel. KW - Mill Scale KW - Quenched KW - Residual Stress KW - Tempered High Strength Steel KW - Thermo-Mechanical Controlled Process KW - Welding PY - 2014 DO - https://doi.org/10.4028/www.scientific.net/AMR.996.457 SN - 1022-6680 SN - 1662-8985 VL - 996 SP - 457 EP - 462 PB - Trans Tech Publ. CY - Zurich AN - OPUS4-31443 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Stress Build-Up during Mulitlayer Welding with Novel Martensitic Filler Materials N2 - Neuartige sogenannte Low-Transformation-Temperature (LTT)- Schweißzusätze weisen eine chemische Zusammensetzung auf, welche die Martensitbildung zu vergleichsweise niedrigen Temperaturen verschiebt. Dies wirkt sich maßgeblich auf die nach dem Schweißen vorliegenden Eigenspannungen aus. Obwohl dazu zahlreiche Veröffentlichungen vorliegen, blieben die Wirkzusammenhänge zwischen Umwandlungstemperatur und Schweißeigenspannungen bislang ungeklärt. Aus diesem Grund wurde in der vorliegenden Arbeit ein Versuch in einer Großprüfanlage durchgeführt, um den Einfluss der Martensitumwandlung während des Mehrlagenschweißens zu analysieren. Die In-Prozess-Beobachtung der auftretenden Kräfte und Momente offenbarte, dass die Eigenspannungsreduktion vom jeweils umwandelnden Volumen abhängt. Die Analyse der Schweißeigenspannungen verdeutlichte, dass die angestrebte Eigenspannungsbeeinflussung durch den Zusatzwerkstoff stark von den Randbedingungen (d. h. Nahtaufbau, Blechdicke) abhängt und einer Bewertung im jeweiligen Anwendungsfall bedarf. N2 - Controlling the level of mostly detrimental residual stresses already during the welding process would be highly attractive as time and cost consuming post processing may be prevented. Innovative Low Transformation Temperature (LTT-) filler materials are specially designed for Controlling weld residual stresses by means of adjusted martensite formation already during welding. Numerous publications can be found on this issue, but they provide only little insight into the interaction between martensite formation and resulting welding residual stresses. Within this study a component weld test was performed in a special large-scale testing facility. In-situ load analysis revealed that the amount of stress reduction during deposition of the individual weld runs is dependent on the weld volume undergoing phase transformation related to the shrinking volume. The residual stresses found alter welding show that the desired residual stress control by using LTT alloys is sensitive to welding boundary conditions (i. e. weld geometry, plate thickness) and to be evaluated separately for varying weld scenarios. T2 - Spannungsentstehung während des Mehrlagenschweißens mit einem neuartigen martensitischen Schweißzusatz KW - Residual stresses KW - LTT filler material KW - Martensite KW - Phase transformation KW - Welding KW - Eigenspannungen KW - LTT-Zusatzwerkstoff KW - Martensit KW - Phasenumwandlung KW - Schweißen PY - 2014 DO - https://doi.org/10.3139/105.110210 SN - 2194-1831 SN - 1867-2493 VL - 69 IS - 2 SP - 80 EP - 88 PB - Hanser CY - München AN - OPUS4-30719 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bhatti, A.A. A1 - Barsoum, Z. A1 - Van der Mee, V. A1 - Kromm, Arne A1 - Kannengießer, Thomas T1 - Fatigue strength improvement of welded structures using new low transformation temperature filler materials N2 - The results reported in this research study are part of a larger EU RFCS (Research Fund for Coal and Steel) project where the aim is to study the fatigue behavior of improved welds in high strength steels by utilizing different improvement techniques. In this particular study LTT (Low Transformation Temperature) weld filler material have been investigated and their possibility to improve the fatigue strength. The characteristic of these filler material is that they undergo phase transformation at temperature close to room temperature which will reduce the tensile residual stress in the weld and in some cases result in compressive residual stresses. Two different LTT alloy compositions have been developed, with different Ms (Martensite Start) temperatures in order to study the amount of tensile/compressive residual stresses produced by these wires. Welding residual stress measurements were carried out by X-ray diffraction technique. Plates with welded longitudinal attachments were fabricated in 700 MPa and 960 MPa steel grades using different LTT filler materials. These specimens were fatigue tested in constant and variable amplitude loading and the fatigue test results were compared with results from specimen welded with conventional weld filler material. KW - Residual stresses KW - LTT KW - Welded joints KW - Fatigue testing PY - 2013 DO - https://doi.org/10.1016/j.proeng.2013.12.074 SN - 1877-7058 VL - 66 SP - 192 EP - 201 PB - Elsevier Ltd. CY - Amsterdam [u.a.] AN - OPUS4-30609 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kromm, Arne A1 - Van der Mee, V. A1 - Kannengießer, Thomas A1 - Kalfsbeek, B. T1 - Properties and weldability of modified low transformation termperature filler wires N2 - Low transformation temperature (LTT) alloys allow to control residual stresses already during the welding process. Especially high-strength structural steel applications may benefit from the LTT effect as they are sensitive to residual stresses due to a limited ductility. Within this study, two modified LTT alloys were tested concerning their weldability under varying conditions. Beside the transformation behavior, basic material properties were determined from all weld metal. Hot cracking as well as cold cracking susceptibility was evaluated using specific tests. The materials' capability for residual stress control was characterized by online measurements of the occurring loads during double-sided multipass fillet welding in a special test facility. Varying heat control parameters were found to affect the stress buildup significantly. In the specific case, the results revealed that higher working temperatures may favor lower stress buildup despite the higher overall heat input. Local residual stress measurements using X-ray diffraction support this finding. KW - Weldability KW - Filler materials KW - Wire KW - Temperature KW - Transformation PY - 2015 DO - https://doi.org/10.1007/s40194-014-0215-y SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 3 SP - 413 EP - 425 PB - Springer CY - Oxford AN - OPUS4-33066 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schasse, R. A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Mente, Tobias T1 - Residual stresses in repair welds of high-strength low-alloy steels N2 - Residual stresses are often the cause for cracks in weld constructions. That is why the residual stress level, induced by manufacturing process, plays a crucial role. The present study aims on the effect of multiple repair weld procedures on a high-strength structural steel S690QL. The widespread technology of carbon arc-air gouging was applied. The weld zone and the heat-affected zone (HAZ) were subjected to multiple thermal cycles by gouging and subsequent repair welding. The investigations were focused on the change of the residuals stresses, the impact on the microstructure and the changes for the mechanical properties of the repair welded joint. The residual stresses were determined by X-ray diffraction. The results have shown a significant dependence for the residual stress levels from the repair cycle. In addition, distinctive changes in microstructures and hence mechanical properties occurred. The fusion line of the repair weld and the adjacent HAZ are the most critical areas. This is where the loss of ductility is most pronounced. KW - Residual stresses KW - High-strength steels KW - Brittle fracture PY - 2015 DO - https://doi.org/10.1007/s40194-015-0257-9 SN - 0043-2288 SN - 1878-6669 VL - 59 IS - 6 SP - 757 EP - 765 PB - Springer CY - Oxford AN - OPUS4-34974 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kannengießer, Thomas A1 - Kromm, Arne A1 - Gibmeier, J. A1 - Rethmeier, Michael T1 - In-situ-Analyse der Phasenumwandlungskinetik während des Schweißens N2 - Zugeigenspannungen, wie sie beim Schweißprozess durch inhomogene Temperaturverteilungen und Schrumpfungen hervorgerufen werden, können die Lebensdauer geschweißter Verbindungen signifikant herabsetzen. Eine neue und außerordentlich attraktive Methode, um Druckeigenspannungen bereits während des Schweißens gezielt einzustellen, gelingt mit sogenannten LTT (Low Transformation Temperature)-Legierungen. LTT-Legierungen weisen eine martensitische Phasenumwandlung bei relativ niedrigen Temperaturen auf, wobei die damit verbundene Volumenexpansion zu einer Reduktion der Schrumpfeigenspannungen bzw. Erzeugung von Druckeigenspannungen führt. Zum direkten Nachweis der Phasenumwandlungen und der damit verbundenen resultierenden Schweißeigenspannungen wurden erstmals In-situ-Schweißexperimente unter Nutzung hoch energetischer, polychromatischer Synchrotronstrahlung (Weißstrahl) realisiert, um die Umwandlungskinetik während eines realen Schweißprozesses und die daraus resultierenden Schweißeigenspannungen zu analysieren. Es wird gezeigt, dass mit LTT-Legierungen signifikante Druckeigenspannungen in der Schweißnaht erreicht werden. PY - 2010 SN - 0025-5300 VL - 52 IS - 4 SP - 204 EP - 210 PB - Hanser CY - München AN - OPUS4-21219 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - In-situ synchrotron diffraction and digital image correlation technique for characterizations of retained austenite stability in low-alloyed transformation induced plasticity steel N2 - Direct measurement and quantification of phase transformation in a low-alloyed transformation induced plasticity steels depending on the tensile load as well as determination of the real true stress and true strain values were carried out in-situ using high energy synchrotron radiation. Digital image correlation technique was used to quantify more precisely the true strain values. The aim of the work was to obtain a better understanding of the phase transformation of commercial low-alloyed transformation induced plasticity steel depending on the true strain and true stress values. KW - Transformation induced plasticity KW - In-situ synchrotron diffraction KW - Austenite stability KW - Digital image correlation PY - 2010 DO - https://doi.org/10.1016/j.scriptamat.2010.08.007 SN - 1359-6462 SN - 1872-8456 VL - 63 IS - 12 SP - 1149 EP - 1152 PB - Elsevier CY - Oxford AN - OPUS4-22164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heinze, Christoph A1 - Kromm, Arne A1 - Schwenk, Christopher A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - Welding residual stresses depending on solid-state transformation behaviour studied by numerical and experimental methods N2 - The development of high-strength structural steels with yield strengths up to 1000 MPa results in the requirement of suitable filler materials for welding. Recently designed low transformation temperature (LTT) alloys offer appropriate strength. The martensitic phase transformation during welding induces compressive residual stress in the weld zone. Therefore, the mechanical properties of welded joints can be improved. The present paper illustrates numerical simulation of the residual stresses in LTT-welds taking into account the effect of varying Ms/Mf-temperatures, and therefore different retained austenite contents, on the residual stresses. Residual stress distributions measured by synchrotron diffraction are taken as evaluation basis. A numerical model for the simulation of transformation affected welds is established and can be used for identification of appropriate Ms-temperatures considering the content of retained austenite. KW - Welding simulation KW - Residual stress KW - Low transformation temperature filler material KW - Martensitic transformation KW - Retained austenite PY - 2011 DO - https://doi.org/10.4028/www.scientific.net/MSF.681.85 SN - 0255-5476 VL - 681 SP - 85 EP - 90 PB - Trans Tech Publications CY - Aedermannsdorf, Switzerland AN - OPUS4-23357 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - In-situ analysis of solid state phase transformation in TRIP-aided steels by synchrotron diffraction N2 - Energy dispersive synchrotron diffraction (EDXRD) analysis and 3 dimensional digital image correlations were conducted to investigate the stress and strain effected transformation behavior during tensile loading of low alloyed TRansformation Induced Plasticity (TRIP) steel. This technique allowed for phase specific stress measurement during certain tensile load steps in the elastic and also plastic regime. Additionally the simultaneous determination of the load dependent phase content was realized. The results show that the martensite transformation starts only after exceeding the overall yield point and is finished before reaching the uniform elongation, whereas a large portion of the austenite remains unchanged in the structure. Furthermore, the martensite transformation related to the stress in the γ-phase and α-phase was analyzed and quantified. KW - Synchrotron KW - EDXRD KW - Phase transformation KW - TRIP steel KW - Digital image correlation KW - Residual stress PY - 2011 UR - https://www.jstage.jst.go.jp/article/qjjws/29/3/29_3_81s/_pdf DO - https://doi.org/10.2207/qjjws.29.81s SN - 0288-4771 VL - 29 IS - 3 SP - 81 EP - 85 CY - Tokyo, Japan AN - OPUS4-24693 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brauser, Stephan A1 - Kromm, Arne A1 - Dabah, Eitan A1 - Kannengießer, Thomas A1 - Rethmeier, Michael T1 - Thermal stability of retained austenite in low alloyed TRIP-steel determined by high energy synchrotron radiation N2 - TRIP-steels offer a good combination between strength and ductility. Therefore TRIP-steels are widely used in the automobile industries. The aim of this work is to study the stability of involved phases during heating and to identify the kinetics of the occuring phase transformations. For that purpose, in-situ diffraction measurements, using high energy synchrotron radiation were conducted. The analysis revealed the decomposition of the metastable austenitic phase into carbide and ferrite along the heating process and the regeneration of the austenite by further heating of the sample. KW - Austenite stability KW - Phase transformation KW - TRIP steel KW - Energy dispersive synchrotron X-ray diffraction PY - 2014 DO - https://doi.org/10.4028/www.scientific.net/MSF.772.129 SN - 0255-5476 VL - 772 SP - 129 EP - 133 PB - Trans Tech Publications CY - Aedermannsdorf, Switzerland AN - OPUS4-29700 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -