Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (149)
- Beitrag zu einem Tagungsband (92)
- Vortrag (56)
- Beitrag zu einem Sammelband (25)
- Forschungsbericht (15)
- Sonstiges (4)
- Buchkapitel (3)
- Corrigendum (2)
- Posterpräsentation (2)
- Dissertation (1)
Schlagworte
- Welding (39)
- Residual stresses (32)
- Eigenspannungen (27)
- Hydrogen (22)
- Residual stress (19)
- Restraint (17)
- Wasserstoff (17)
- Hochfester Stahl (16)
- MAG-Schweißen (16)
- High-strength steels (15)
- Schweißen (15)
- Phase transformation (14)
- Hydrogen embrittlement (12)
- Additive Fertigung (11)
- Cold cracking (11)
- High-strength steel (11)
- Wärmeführung (11)
- Hochfester Feinkornbaustahl (10)
- Kaltrisssicherheit (10)
- Process parameters (10)
- Diffusion (9)
- Hydrogen diffusion (9)
- Ultrasonic-assisted milling (9)
- Additive manufacturing (8)
- Energy dispersive diffraction (8)
- Hot cracking (8)
- LIBS (8)
- MAG welding (8)
- Measurement (8)
- Neutron radiography (8)
- Creep-resistant steel (7)
- Heat control (7)
- ISO 3690 (7)
- Martensite (7)
- Residual Stress (7)
- Surface integrity (7)
- Ultraschallunterstütztes Fräsen (7)
- GMA welding (6)
- Hydrogen assisted cracking (6)
- In situ measurement (6)
- LTT (6)
- Microstructure (6)
- Alloy 36 (5)
- Austenitic stainless steels (5)
- Digital image correlation (5)
- Duplex stainless steel (5)
- Duplex stainless steels (5)
- High strength steel (5)
- Kaltriss (5)
- Large-scale test (5)
- Legierungsmodifikation (5)
- Oberflächenintegrität (5)
- Steel (5)
- Submerged arc welding (5)
- Synchrotron (5)
- Synchrotron radiation (5)
- Transformation (5)
- Weldability (5)
- Alloy modification (4)
- Carrier gas hot extraction (4)
- Diffusible hydrogen (4)
- Fügetechnik (4)
- GMAW (4)
- Heat affected zone (4)
- Hochfeste Feinkornbaustähle (4)
- Hot extraction (4)
- Kaltrisse (4)
- Kaltrissprüfung (4)
- Low transformation temperature (4)
- Mechanical properties (4)
- Rissbildung (4)
- Round robin test (4)
- Solidification cracking (4)
- Stress relief cracking (4)
- TIG welding (4)
- Temperature (4)
- WEZ-Erweichung (4)
- Werkstofffragen (4)
- Werkzeugverschleiß (4)
- X-ray refraction (4)
- Cooling rate (3)
- Cracking (3)
- EDXRD (3)
- Filler material (3)
- Forschung (3)
- Gas metal arc welding (3)
- Gefügedegradation (3)
- Heat treatment (3)
- Heißriss (3)
- High-Strength Steel (3)
- Hydrogen assisted cold cracking (3)
- In situ (3)
- Interpass temperature (3)
- Laser-GMA-hybrid welding (3)
- Low alloy steels (3)
- MVT-Test (3)
- Microalloyed steels (3)
- Neutron diffraction (3)
- Neutron tomography (3)
- Numerical simulation (3)
- Phase specific residual stresses (3)
- Plasma-transferred arc welding (3)
- Post weld heat treatment (3)
- Reparatur (3)
- Residual Stresses (3)
- Restraint intensity (3)
- Stainless steels (3)
- Steels (3)
- Strength (3)
- TRIP steel (3)
- Thermodynamische Simulation (3)
- UP-Schweißen (3)
- Weldability tests (3)
- Windenergie (3)
- X-ray diffraction (3)
- 13CrMoV9-10 (2)
- AISI 304L (2)
- Additive Manufacturing (2)
- Aluminium alloy (2)
- Austenite (2)
- Austenite stability (2)
- Austenitic stainless steel (2)
- Bauteilprüfung (2)
- Blister (2)
- Chemical composition (2)
- Component welding (2)
- Computed tomography (2)
- Cooling (2)
- Energy dispersive X-ray diffraction (2)
- Erstarrungsriss (2)
- Festigkeit (2)
- Filler materials (2)
- Grain growth (2)
- Hardness (2)
- Heat-affected zone (2)
- Heißrisse (2)
- High-strength structural steel (2)
- Higher-strength steels (2)
- Hot cracks (2)
- Hydrogen measurement (2)
- Hydrogen-assisted cracking (2)
- Höherfester Feinkornbaustahl (2)
- Imaging (2)
- Implant test (2)
- Implant-Test (2)
- In-situ diffraction (2)
- In-situ measurement (2)
- In-situ phase analysis (2)
- Influencing factors (2)
- Iron (2)
- LTT (Low Transformation Temperature) (2)
- LTT filler material (2)
- Laser welding (2)
- Loading (2)
- Local weld displacement (2)
- Low temperature (2)
- Martensite transformation (2)
- Mercury (2)
- Metal cored wire electrode (2)
- Metallurgie (2)
- Metallurgische Fragen (2)
- Mikrolegierungseinfluss (2)
- Mikrolegierungseinflüsse (2)
- Modifizierter Sprühlichtbogen (2)
- Offshore (2)
- Parent material (2)
- Phase Transformation (2)
- Practical investigations (2)
- Preheating (2)
- Prüfverfahren (2)
- Reaction Stress (2)
- Reaction force (2)
- Reheat cracking (2)
- Repair-welding (2)
- Reparaturschweißen (2)
- Schrumpfbehinderung (2)
- Schutzgasschweißen (2)
- Schwingfestigkeit (2)
- Shrinkage restraint (2)
- Solid wire electrodes (2)
- Spannungsrelaxationsriss (2)
- Stainless steel (2)
- Stress build up (2)
- Stress distribution (2)
- Studie (2)
- Supermartensit (2)
- TEKKEN (2)
- TEKKEN-Test (2)
- Temperature distribution (2)
- Testing (2)
- Tests (2)
- Thermisches Ausfugen (2)
- Tool wear (2)
- Varestraint test (2)
- Vertical position (2)
- WAAM (2)
- WRC 1992 diagram (2)
- Weld metal (2)
- Weld zone (2)
- Welded joints (2)
- Welding position (2)
- Welding residual stress (2)
- Welding residual stresses (2)
- Welding simulation (2)
- Werkstoffe (2)
- Wärmeführung beim Schweißen (2)
- X-Ray Diffraction (2)
- X-Ray Diffraction (XRD) (2)
- XRD (2)
- Yield strength (2)
- Zerspankräfte (2)
- 1.4306 (1)
- 1.4565 (1)
- 2-D Welding Simulation (1)
- 2101 duplex stainless steel (1)
- 3D Scanning (1)
- 3D-Dehnungsanalyse (1)
- ADXRD (1)
- AGIL (1)
- Absorption (1)
- Acicular ferrite (1)
- Alloy 602 CA (Material No.: 2.4633, NiCr25FeAlY) (1)
- Alloy 602 CA (Werkstoff-Nr.: 2.4633, NiCr25FeAlY) (1)
- Alloy 602 CA (material-No.: 2.4633, NiCr25FeAlY) (1)
- Alloy 617 (1)
- Alloy addition (1)
- Aluminium alloys (1)
- Aluminiumlegierung (1)
- Analyser based imaging (1)
- Analyser-based imaging (1)
- Analysis technique (1)
- Anlagenbau (1)
- Arc Welding (1)
- Arc welding (1)
- Aufmischung (1)
- Austenit (1)
- Austenitic (1)
- BAM Windenergie Fügetechnik (1)
- Bauteilschweißungen (1)
- Bauteiltest (1)
- Bedarf (1)
- Beta-21S (1)
- Biegemoment (1)
- Brittle fracture (1)
- CT (1)
- Carbon arc-air gouging (1)
- Carbon steels (1)
- Carrier gas (1)
- Carrier gas analysis (1)
- Charpy V-notch impact test (1)
- Charpy toughness (1)
- Chemical analysis (1)
- Clamping (1)
- Closed test sequence (1)
- Co-Cr-alloy (1)
- Cobalt-chromium alloy (1)
- Cold Cracking (1)
- Cold Cracking Test (1)
- Cold cracking safety (1)
- Commission II (1)
- Component (1)
- Component Test (1)
- Component Testing (1)
- Component design (1)
- Component manufatcturing (1)
- Component test (1)
- Component testing (1)
- Component tests (1)
- Component-like test (1)
- Comprehensive study (1)
- Computed tomography (CT) (1)
- Conclusive test sequences (1)
- Controlled tensile weldability test (1)
- Corrosion (1)
- Corrosion tests (1)
- Crack criterion (1)
- Crack formation (1)
- Creep resistant steel (1)
- Creep resisting materials (1)
- Crevice corrosion (1)
- Cutting forces (1)
- Cutting tool (1)
- DED-arc (1)
- DVS-Richtlinie 1006 (1)
- Dduplex stainless steel (1)
- Defects (1)
- Deformation (1)
- Dehngeschwindigkeit (1)
- Dehnung (1)
- Dickblech (1)
- Diffraction-elastic constants (1)
- Dilatometry (1)
- Dilution (1)
- EDS (1)
- Effusion (1)
- Einspanngrad (1)
- Eisenaluminid (1)
- Electrochemical permeation (1)
- Embrittlement (1)
- Energy dispersive X-ray diffraction (EDXRD) (1)
- Energy dispersive synchrotron X-ray diffraction (1)
- Ensaios (1)
- Ermüdungsfestigkeit (1)
- Ersatzgeometrie (1)
- Evaporation (1)
- Experimental design (1)
- External load test (1)
- Extraction method (1)
- FEM-simulation (1)
- Fatigue (1)
- Fatigue Strength (1)
- Fatigue design (1)
- Fatigue strength (1)
- Fatigue testing (1)
- Ferrit (1)
- Fibre laser (1)
- Finit Element Method (1)
- Flux cored wire electrodes (1)
- Formation water (1)
- Forschungsprojekt (1)
- Fractography (1)
- Fracture Mechanics (1)
- Frames (1)
- Fülldrahtelektroden (1)
- GAPSI 16 (1)
- GMA-laser-hybrid welding (1)
- GMAwelding (1)
- GTA welding (1)
- Galvanic corrosion (1)
- Gas calibration (1)
- Gas shielded arc welding (1)
- Geschlossene Prüfkette (1)
- Girders (1)
- HAZ-softening (1)
- HEat control (1)
- HSLA steel (1)
- Hardness measurement (1)
- Heat (1)
- Heat Control (1)
- Heat control in welding (1)
- Heat input (1)
- Heat-affected zone softening (1)
- Heating (1)
- Heften (1)
- Heißrissneigung (1)
- Heißrisssicherheit (1)
- Heißrisstest (1)
- High alloyed steel AISI 304L (1)
- High energy synchrotron diffraction (1)
- High energy synchrotron radiation (1)
- High stength steels (1)
- High strength steels (1)
- High strength structural steel (1)
- High strength structural steels (1)
- High-strength Steel (1)
- High-strength filler metals (1)
- High-strength steel filler metal (1)
- High-strength structural steels (1)
- Hochfest (1)
- Hochfeste Stähle (1)
- Hochlegiert (1)
- Hole drilling method (1)
- Hollow sections (1)
- Hot cracking resistance (1)
- Hybrid (1)
- Hybridschweißen (1)
- Hydrogen Induced Cracking (1)
- Hydrogen absorption (1)
- Hydrogen assisted cracking (HAC) (1)
- Hydrogen concentration (1)
- Hydrogen desorption (1)
- Hydrogen effusion (1)
- Hydrogen embrittlement (HE) (1)
- Hydrogen induced cracking (1)
- Hydrogen pickup (1)
- Hydrogen trapping (1)
- Höherfester Stahl (1)
- I-Girder (1)
- I-Träger (1)
- I-girder (1)
- I-shape sections (1)
- IBESS Approach (1)
- IIW (1)
- IN725 (1)
- IRc-Test (1)
- In situ synchrotron X-ray diffraction (1)
- In-situ (1)
- In-situ observation (1)
- In-situ synchrotron X-ray diffraction (1)
- In-situ synchrotron diffraction (1)
- Influence (1)
- Inherent Strain (1)
- Intensity of Restraint (1)
- Intensity of restraint (1)
- Intergranular corrosion (1)
- Iron aluminide (1)
- Kaltrissbildung (1)
- Kaltrisstests (1)
- Kerbschlagzähigkeit (1)
- Konstruktiver Einfluss (1)
- LIBS TIG welding (1)
- LTT alloy (1)
- LTT filler materials (1)
- LTT filler metal (1)
- LTT-Legierung (1)
- LTT-Zusatzwerkstoff (1)
- Large scale test (1)
- Laser GMA hybrid welding (1)
- Laser hybrid welding (1)
- Laser plasma (1)
- Laser-based additive manufacturing (1)
- Laserstrahl-MSG-Hybrid-Schweißen (1)
- Laserstrahl-MSG-Hybridschweißen (1)
- Laserstrahlschweißen (1)
- Lattice distortions (1)
- Lean-duplex stainless steel (1)
- List of questions (1)
- Local Weld Geometry (1)
- Local weld deformation (1)
- Local weld strain (1)
- Lokale und globale Dehnungsmessung (1)
- Low (1)
- Low Transformation Temperature (1)
- Low Transformation Temperature filler wire (1)
- Low temperature transformation (1)
- Low themperature (1)
- Low transformation (1)
- Low transformation temperature (LTT) alloy (1)
- Low transformation temperature filler material (1)
- Low transformation temperature filler materials (1)
- Low transformation temperature filler wire (1)
- MAG Welding (1)
- MVT (1)
- Machining (1)
- Martensit (1)
- Martensitic transformation (1)
- Material questions (1)
- Mathematical models (1)
- Mechanical Engineering (1)
- Mechanics of Materials (1)
- Metal vapor (1)
- Metall-Schutzgasschweißen (1)
- Metallschutzgasschweißen (1)
- Metallurgical questions (1)
- Metals and Alloys (1)
- Metastabiler austenitischer Chrom-Nickel-Stahl (1)
- Microalloyed Steels (1)
- Microalloyed steel (1)
- Microalloying influences (1)
- Microcracking (1)
- Microfocus X-ray computer tomography (μCT) (1)
- Mikrolegierungselemente (1)
- Mill Scale (1)
- Mill scale (1)
- Minimum Waiting Time (1)
- Minimum waiting time (1)
- Modification of structural morphology (1)
- Modified varestraint transvarestraint (MVT) hot cracking test (1)
- Multi-pass weld (1)
- Multi-pass welding (1)
- Multi-run weld (1)
- Multilayer Welding (1)
- Multirun welding (1)
- Nahtgeometrie (1)
- Nd:YAG (1)
- Neutron imaging (1)
- Ni alloy (1)
- Ni-base alloy (1)
- Nickel alloys (1)
- Nickel base material (1)
- Niobium carbide (1)
- Numerical Modeling (1)
- Numerical Simulation (1)
- Numerical analysis (1)
- Numerische Simulation (1)
- Offshore steel grade (1)
- Offshore steels (1)
- Orbital TIG welding (1)
- Permeation (1)
- Permeation experiments (1)
- Perspektiven (1)
- Phase transformation temperature (1)
- Phasenumwandlung (1)
- Photon beam welding (1)
- Pipeline (1)
- Pitting corrosion (1)
- Plasma welding (1)
- Plasma-Pulver-Auftragschweißen (1)
- Plasticity-based Analysis (1)
- Plate girders (1)
- Plated structures (1)
- Positional welding (1)
- Positionsschweißen (1)
- Post Weld Heat Treatment (PWHT) (1)
- Post-weld heat treatment (1)
- Powder (1)
- Pressure vessel steels (1)
- Probenbeanspruchungsgeschwindigkeit (1)
- Process conditions (1)
- Process stability (1)
- Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten (1)
- Prozesse (1)
- Prüfung und Simulation (1)
- QT steel (1)
- Quality control (1)
- Quenched (1)
- Radiation welding (1)
- Radiography (1)
- Reaction moment (1)
- Reaktionskräfte (1)
- Real-time operation (1)
- Reference lists (1)
- Regelwerke (1)
- Repair welding (1)
- Residual stress analysis (1)
- Residual stress reduction (1)
- Retained austenite (1)
- Risssicherheit (1)
- Rutile tubular cored wire (1)
- Röntgenrefraktion (1)
- SRC (1)
- Schallemission (1)
- Schweißeigenspannungen (1)
- Schweißen von hochfesten FKB (1)
- Schweißnahtfehler (1)
- Schweißnahtunregelmäßigkeiten (1)
- Schweißparameter (1)
- Schweißprozess (1)
- Schweißprozessparameter (1)
- Schweißsicherheit (1)
- Schweißverbindung (1)
- Sectioning Method (1)
- Sectioning method (1)
- Shielding gas (1)
- Soldabilidade (1)
- Solid wire (1)
- Solid wire electrode (1)
- Solid-state laser (1)
- Solubility (1)
- Spannungen (1)
- Spannungsrelaxationsrisse (1)
- Specimen loading speed (1)
- Speed (1)
- Stability Design (1)
- Stahl (1)
- Stainless Steel (1)
- Strain field measurement (1)
- Strain-free lattice spacing (1)
- Stress (1)
- Stress Relief Cracking (SRC) (1)
- Stress corrosion (1)
- Stress strain distribution (1)
- Structural optimization (1)
- Structural steels (1)
- Structural stiffness (1)
- Sub-Merged Arc Welding (1)
- Supermartensitic Steel (1)
- Supermartensitic stainless steel (1)
- Supermartensitic stainless steels (1)
- Supermartensitics (1)
- Synchrotron Diffraction (1)
- Synchrotron diffraction (1)
- TDS (1)
- TIG (1)
- Technologie (1)
- Temperature alloys (1)
- Tempered High Strength Steel (1)
- Tensile loading (1)
- Tensile tests (1)
- Test velocity (1)
- Thermal Desorption Spectroscopy (TDS) (1)
- Thermal conductivity device (1)
- Thermal desorption analysis (1)
- Thermo-Mechanical Controlled Process (1)
- ThermoCalc (1)
- Thermodynamic simulation (1)
- Thermodynamische Modellierung (1)
- Thick-walled (1)
- Titanium alloys (1)
- Titanium hydride (1)
- Toughness (1)
- Traglastverhalten (1)
- Transformation induced plasticity (1)
- Transformation temperature (1)
- Transformation-induced plasticity (TRIP) (1)
- Transverse tensile test (1)
- Trapping (1)
- Trinca Induzida por Hidrogenio (1)
- Trinca a Frio (1)
- Tubular cored electrode (1)
- Tubular cored wire electrodes (1)
- Unalloyed steels (1)
- Vacuum hot extraction (1)
- Varestraint testing (1)
- Varestraint-Test (1)
- Vertical down (1)
- Vertical position down (1)
- Vertical up (1)
- Vickers hardness (1)
- WEZ Erweichung (1)
- Wasserstoffbedingte Eigenschaftsdegradation (1)
- Wasserstoffunterstützte Rissbildung (1)
- Wasserstoffversprödung (1)
- Weld filler (1)
- Weld imperfections (1)
- Weld metal cracking (1)
- Weld residual stress (1)
- Weld residual stresses (1)
- Welded Joints (1)
- Welded pipelines (1)
- Welding metallurgy (1)
- Welding speed (1)
- Welding stresses (1)
- Werkstoff (1)
- Widerstandspunktschweißen (1)
- Wind Energy (1)
- Wind energy (1)
- Wire (1)
- Wire Arc Additive Manufacturing (1)
- Wärmebehandlung (1)
- Wärmenachbehandlung (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray computer tomography (1)
- XRF (1)
- Zusatzwerkstoffe (1)
- carrier gas hot extraction (1)
- hochfeste Feinkornbaustähle (1)
- solidification cracks (1)
- ultraschallunterstütztes Fräsen (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (115)
- 9.4 Integrität von Schweißverbindungen (109)
- 9.2 Versuchsanlagen und Prüftechnik (51)
- 9.0 Abteilungsleitung und andere (29)
- 8 Zerstörungsfreie Prüfung (6)
- 8.5 Röntgenbildgebung (4)
- 8.4 Akustische und elektromagnetische Verfahren (2)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.3 Instrumentelle Analytik (1)
- 5 Werkstofftechnik (1)
Paper des Monats
- ja (6)
This article provides an impression on potentials in applying nowadays welding simulation tools in construction design. This is carried out exemplary on plate girders from two structural steel grades. The calculated residual stresses are compared with measurements by sectioning method. It has been repeatedly stated that present Eurocode models fail to approximate the residual stresses. Especially for high strength steel (HSS) only limited information is available on realistic occurring residual stresses in typical I-girders. The investigations are aimed to give further guidance on these values. A few proposals on advanced models are discussed.
Is it reasonable to restrict ISO 3690 any longer to the determination of the weld metal hydrogen content of ferritic steel?
In what respect is the determination of the content of the diffusible and of the total hydrogen content, respectively, (still) merely a research task (supermartensite, duplex materials, austenite, magnesium, aluminium), or is there actually a demand in industry and is there already a first cause for monitoring in view of damage prevention, respectively?
Is there a need, arising from the development of materials and filler materials and from their intended applications, for more extensive standards dealing with hydrogen analyses for these materials?
Which parts of ISO 3690 could also be applied to any other metallic material/filler material, if necessary, and where would a complete alteration be required, respectively?
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.
The performance and safety of welded high-strength low-alloyed steel (HSLA) components are substantially affected by the stresses occurring during and after welding fabrication, especially if welding shrinkage and distortion are severely restrained. The surrounding structure of the whole component affects loads in the far-field superimposing with welding stresses in the near-field of the weld. In this study a unique testing facility was used to restrain shrinkage and bending while analyse multiaxial far-field loads (max. 2 MN) during assembly of thick-walled component. A novel approach for the assessment of the in-situ-measured far-field data in combination with the actual weld geometry was elaborated. For the first time, analyses of the global bending moments of restrained welds based on the neutral axis of the actual weld load bearing section were achieved. Hence, far-field measurements offered the possibility to determine critical near-field stresses of the weld crosssections for the entire joining process. This work presents the approach for far-to-near field in-situ determination of stresses in detail for the 2-MN-testing system based on an extensive experimental work on HSLA steel welds, which demonstrates sources and consequences of these high local welding stresses. Thus, it was clarified, why the first weld beads are crucial regarding welding stresses and cold cracking, which is well known, but has never been measured so far. Accompanying analyses using X-ray diffraction (XRD) after welding show effects on local residual stress distributions. These analyses indicated viable prospects for stress reduction during assembly of thick-walled HSLA steel components.
In modernen Stahlkonstruktionen werden immer häufiger hochfeste Feinkornbaustähle erfolgreich eingesetzt. Dies resultiert aus dem aktuellen Bestreben, leichte Komponenten zu fertigen und damit die Energie- und Ressourceneffizienz zu steigern. Die Herausforderungen an die Auslegung und Herstellung geschweißter Bauteile nimmt jedoch mit steigenden Festigkeiten und abnehmenden Dehnungsreserven der eingesetzten Werkstoffe zu. So können hohe Schweißeigenspannungen die Beanspruchbarkeit und Bauteilsicherheit kritisch herabsetzen. Untersuchungen zeigten bereits deutliche Einflüsse von Werkstoff, Wärmeführung sowie Schweißprozessparametern und der um-gebenden Konstruktion der Schweißnaht auf den Beanspruchungszustand geschweißter Bauteile. Der Einsatz moderner modifizierter Sprühlichtbogenprozesse (mod.SLB) gestattet in diesen Zusammenhang neben den bekannten wirtschaftlichen Vorteilen das Schweißen einer deutlich schmaleren Nahtgeometrie. Aufgrund des resultierenden reduzierten Gesamtwärmeeintrages sind deutlich geringere schweißbedingte Beanspruchungen und eine höhere Beanspruchbarkeit hochfester Schweißkonstruktionen erreichbar. Unter Nutzung spezieller Prüfanlagen konnten mehrlagige Schweißexperimente zur Analyse des Einflusses der Nahtgeometrie auf die Eigenspannungsausbildung und Gesamtbeanspruchung hochfester Schweißverbindungen bei bauteilähnlichen Einspannbedingungen durchgeführt werden. Für die reduzierten Nahtvolumina zeigte sich eine signifikante Absenkung des Beanspruchungsniveaus während des Schweißens und nach der Abkühlung.
In situ EDXRD study of MAG-welding using LTT weld filler materials under structural restraint
(2017)
Welding using low transformation temperature (LTT) filler materials is an innovative approach to mitigate detrimental welding residual stresses without cost-intensive post weldtreatments. Due to the local Generation of compressive residual stresses in the weld line by means of a delayed martensite transformation a significant enhancement of the cold cracking resistance of highly stressed welded components can be expected. For the effective usage of These materials a deeper understanding of the microstructural evolution inside the weld material is necessary to determine the complex processes that cause the residual stress formation during welding. Solid-state phase transformation kinetics and the evolution of strain in LTT weld filler materials are monitored in-situ at the instrument ID15A at the ESRF in Grenoble, France. The transferability to real components is implemented by using a realistic MAG welding process under consideration of structural restraint. During welding of multilayer joints, the phase Transformation and phase specific strain evolution of each individual layer is investigated in transmission geometry by means of energy-dispersive X-ray diffraction EDXRD using high energy synchrotron Radiation with a counting rate of 2.5 Hz. The measurement results of a 10% Cr / 10% Ni LTT weld filler are compared to data monitored for the conventional weld filler material G89. The in-situ data clearly indicate a strong effect on the local strain evolution and the formation of compressive strain. This results from the restraint volume expansion during the postponed austenite to martensite transformation of the LTT weld filler, which counteracts the thermal shrinkage. In contrast, for the conventional weld filler material the thermal contraction strains lead to tensile residual strain during welding. Furthermore, the results of in-situ observation during welding Show that the transformation kinetic is dependent on the welding sequence.
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.
Submerged arc welded (SAW) components of creep-resistant low-alloyed Cr-Mo-V steels are used for thick-walled heavy petrochemical reactors (wall-thickness up to 475 mm) as well as employed in construction of modern high-efficient fossil fired power plants. These large components are accompanied by significant restraints during welding fabrication, especially at positions of different thicknesses like welding of nozzles. As a result, residual stresses occur, playing a domi-nant role concerning so-called stress relief cracking (SRC) typically during post weld heat treat-ment (PWHT). Besides specific metallurgical factors (like secondary hardening due to re-precipitation), high tensile residual stresses are a considerable influence factor on SRC. For the assessment of SRC susceptibility of certain materials mostly mechanical tests are applied which are isolated from the welding process. Conclusions regarding the influence of mechanical factors are rare so far. The present research follows an approach to reproduce loads, which occur during welding of real thick-walled components scaled to laboratory conditions by using tests designed on different measures. A large-scale slit specimen giving a high restraint in 3 dimensions by high stiffness was compared to a medium-scale multi-pass welding U-profile specimen showing a high degree of restraint in longitudinal direction and a small-scale TIG-re-melted specimen. The small-scale specimens were additionally subjected to mechanical bending to induce loads that are found during fabrication on the real-scale in heavy components. Results show for all three cases compa-rable high tensile residual stresses up to yield strength with high gradients in the weld metal and the heat affected zone. Those high tensile stresses can be significant for cracking during further PWHT.
Compared to conventional welding consumables using low transformation temperature (LTT) filler materials is an innovative method to mitigate tensile residual stresses due to delayed martensite transformation of the weld. For the effective usage of LTT filler materials, a deeper understanding of the complex processes that lead to the final residual stress state during multipass welding is necessary. Transformation kinetics and the strain evolution of multi-pass welds during welding were investigated in situ at the beamline HEMS@PETRAIII, Germany. Compared to conventional welds, the total strain was reduced and compression strain was achieved when using LTT filler materials. For an optimal use of the LTT effect in the root of multi-pass welds, the alloying concept must be adapted taking care of dilution.
Optimization of welding loads with narrow groove and application of modified spray arc process
(2017)
Current efforts for lightweight design result in a growing application of high-strength fine-grained structural steel in modern constructions, e.g. mobile cranes, with yield strength from 960 MPa. The design of welded structures and welding processes becomes more challenging with increasing material strength and elastic ratios. High residual stresses are able to diminish lifetime, load capacity and component safety and should be avoided. Recent analyses have shown strong influences of heat control and restraint of the weld due to arising reaction stresses, superimposing with local residual welding stresses. Modern inverter technologies allowed the development of numerous modified spray arc processes driven by power source manufacturers, which provide virtually similar features and several benefits, enabling welding of narrower seams with reduced weld volumes and total heat inputs. This research focuses on welding loads due to modified weld seams. The global reaction forces and moments and their superposition with local residual stresses in welded components due to external shrinkage restraints were investigated using a special testing facility and XRD. The restraint intensity, weld seam geometry and welding process were varied for statistical evaluations of resulting welding loads. When welding under restraint, a reduction of the weld seam volume causes significantly lower reaction stress levels.
Der verstärkte Einsatz höherfester Stähle und Zusatzwerkstoffe erfordert ein vertieftes Verständnis der Zusammenhänge zwischen Schweißverfahren, Wärmeeinbringung, Abkühlbedingungen sowie den daraus resultierenden metallurgischen Vorgängen in der Schweißnaht und deren Umgebung. Nur aus dem Zusammenwirken aller Einflussfaktoren lassen sich Strategien ableiten, mit deren Hilfe die Festigkeitseigenschaften bzw. die Lebensdauer von Schweißkonstruktionen in einem Maße verbessert werden können, die den Einsatz höherfester Werkstoffe rechtfertigen und somit deren Leichtbaupotenzial voll ausgenutzt werden kann. Vorgestellt werden einige beispielhafte Untersuchungen an Schweißverbindungen aus höherfesten Feinkornbaustählen zu Interaktionen der Haupteinflussgrößen auf die Kaltrissbildung.
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.
In the last decade, high-strength fine grained steels and welding consumables have gained a strong raise of application ranging from mobile cranes to bridge constructions. However, the cracking susceptibility of these steels increases significantly in correspondence with the achieved improvements in yield strength and the loss in plastic deformation reserves.
In order to determine this behavior a series of different standardized cold cracking tests has been developed. One remaining major problem of these tests is the uncertainty about the quantitative intensity of the restraint conditions as well as the corresponding welding residual stresses.
Consequently, the comparison of different tests and welding conditions as well as the transferability of the results onto real parts is difficult at best. The main topic of this paper is the analysis of the restraint conditions and their link with the welding induced residual stresses. The importance of the given standardized selfrestrained tests and first results about the transferability of
results onto real parts are discussed. The influence of the test specimen geometry on the restraint conditions of the test is investigated for a selected test with numerical Simulation using commercial FEA software. Additionally, the residual stresses caused by the welding process are measured and linked with the restraint conditions which are defined mainly by the geometry parameters.
Finally the transferability of the selected cold cracking test results is validated experimentally. The test results of a multilayer weld on high-strength fine grained steel of real size weldments are investigated. For these experiments a 16 MN large scale testing facility is used which is capable of applying the high reaction forces and clamping conditions found at large scale demonstrator parts.
The results show the importance of the quantitative knowledge of the restraint conditions and the welding residual stresses on the cold cracking resistance.
Today’s light weight design trends lead to a growing application of high-strength structural steels (yield strength ≥ 690 MPa). The mechanical properties of the weld and the component safety have to meet the increased requirements of these steel grades. However, high residual stresses in welded components are detrimental to their safety and integrity. Analyses concerning weld stresses in high-strength steels welded under component related restraint conditions revealed that heat control significantly affects global and local stresses. This occurs especially in highly restrained joints due to superimposing local and global stresses and may cause crack-critical stress-levels. In this study weld tests were performed with plates of high-strength steel in a special test facility. The experimental setup allowed transferring defined restraint conditions to the test welds similarly to real components. Temperature and reaction forces due to restraint were observed online while welding and cooling of multilayer-component MAG-welds. Mobile X-ray diffraction was used for local stress determination in the weld seam areas of the restrained specimens. It was found that interpass temperature has a major influence on the local and global welding forces and stresses. Thus, among the analysed results especially transverse residual stresses of the heat affected zone were strongly affected.
The increased application of higher-strength steels and filler materials necessitates a more profound understanding of the interactions between the welding process, the heat input, the cooling conditions and the resulting metallurgical processes in the weid and its surroundings. Strategies, which help to improve the strength properties and life-time of welded stmctures to such an extent that the utilisation of higher-strength materials can be justified and their lightweight construction potential can thus be exploited to the füll, can only be derived from the interaction between all the influencing factors. Examples of a few investigations on welded joints between higher-strength fine-grained structural steels with regard to the interactions between the main variables influencing the cold cracking are presented in this article.
Duplexstähle besitzen ein zweiphasiges Gefüge und werden aufgrund ihrer verbesserten Schweißeignung gegenüber den Vollausteniten häufig im Anlagen- bzw. Apparatebau eingesetzt. Aufgrund der hohen Abkühlgeschwindigkeit und dem Abbrand von Legierungselementen kommt es zu einer Ferritisierung des Schweißguts und damit zu einer Degradation der mechanischen Eigenschaften. Zur Vorhersage des Phasenverhältnisses im Schweißgut wird das WRC1992-Diagramm genutzt. Dieses Diagramm zeigt einige Ungenauigkeiten und benötigt zur genaueren Vorhersage der Phasenverhältnisse eine Überarbeitung. Um den Einfluss einzelner Elemente auf das Schweißnahtmikrogefüge besser zu verstehen, wurden drahtförmige Schweißzusatzwerkstoffe mit dem Ferrit-Bildner Nb und dem Austenit-Bildner Cu beschichtet und für Schweißungen verwendet. Die Messmethode der Laser-induzierten Plasmaspektroskopie (LIBS) bietet hier eine gute Möglichkeit der in situ Überwachung der chemischen Konzentrationen, während des WIG-Schweißens von Duplexstählen. Die LIBS-Messergebnisse, konnten mit der Ferritnummer und der Schweißnahtmikrostruktur korreliert werden.
For a significant increase in the strength of high-strength fine-grained structural steels with a nominal yield strength ≥690 MPa, the addition of microalloying elements such as Nb and Ti is required. The standard specifications for the chemical composition of these steels (e.g., in EN 10025-6) often only give the manufacturer limit contents to achieve the defined properties. The effect of the alloying elements in the heat affected zone (HAZ) is sometimes completely contrary.
This makes it difficult to adequately predict the batch dependency regarding weldability and the load-bearing behaviour of the welded joint. Three different micro-alloyed steels of the grade S690QL were produced on a laboratory scale, focusing on different Nb and Ti contents. To investigate the tempering effect, these were gas metal arc welded in three layers. In addition to metallographic investigations of individual HAZ areas, thermodynamic phase calculations were carried out using Thermo-Calc, following variations in the chemical composition. This provides an understanding of phase transformation, precipitation growth, and dissolution during welding as a function of temperature and cooling conditions. The results show
a divergent metallurgical behaviour in the HAZ of the three different micro-alloyed steels. Thereby, the Ti micro-alloyed grade showed a strong softening of the HAZ in contrast to the Nb micro-alloyed grade. This can be attributed to a contrary precipitation behaviour during welding.
Mikrolegierungselementen, wie Nb und Ti sind für eine signifikante Festigkeitssteigerung von vergüteten, hochfesten Feinkornbaustählen mit einer Nominalstreckgrenze ≥ 690 MPa unerlässlich. Normvorgaben zur chemischen Zusammensetzung dieser Stähle geben zur Erzielung der vorgeschriebenen Eigenschaften dabei oft nur Grenzgehalte für die Hersteller vor. Die Wirkung der Mikrolegierungselemente bzw. ihrer Karbide und/oder Nitride ist teilweise komplett konträr, insbesondere bei Auflösung und Wiederausscheidung in der WEZ bei identischem Schweißzusatz. Somit wird eine adäquate Vorhersage der Chargenabhängigkeit hinsichtlich der Schweißeignung und des Tragverhaltens der Schweißverbindung erschwert. Eine unerwünschte Eigenschaft ist dabei die Erweichung der WEZ, wie auch u.U. der gegenteilige Effekt der Aufhärtung.
Vor diesem Hintergrund werden im Rahmen eines DFG-Vorhabens systematisch Mikrolegierungs-routen mit variierenden Ti- und Nb-Gehalten des hochfesten und vergüteten Feinkornbaustahls S690QL untersucht. Dazu wird das MAG-Schweißen mit modifizierten Sprühlichtbogen verwendet, welches durch hohe Abschmelzleistung gekennzeichnet ist und schmalere Nahtöffnungswinkel (α = 30°) ermöglicht. An Dreilagen-Schweißungen wird der Effekt der metallurgischen Zusammensetzung in Kombination mit hoher Wärmeeinwirkung auf die Ausbildung einer kritischen WEZ-Gefügezone mit Erweichung und/oder exzessiver Aufhärtung untersucht. Ein besonderes Augenmerk wird auf die Phasenumwandlungen und das Ausscheidungsverhalten im Gefüge der Wärmeeinflusszone gelegt. Neben umfangreichen metallographischen Untersuchungen einzelner WEZ-Bereiche wurden, unter Variation der chemischen Zusammensetzung,
thermodynamische Phasenberechnungen mittels Thermo-Calc durchgeführt. Hierdurch wird ein Verständnis zur Phasentransformation und Ausscheidungswachstum und -auflösung während des Schweißens in Abhängigkeit von Temperatur und Abkühlbedingungen geschaffen. Das Ziel ist es, den Einfluss der Wärmeeinwirkung auf die Gefügeausbildung in der WEZ und dessen mechanischer Eigenschaften zu analysieren. Insbesondere wird hier auf die Auswirkung der unterschiedlichen Mikrolegierungskonzepte (Ti oder Nb) geachtet.
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.
AbstractThe sustainable and resource-efficient production of wind energy plants requires the use of modern high-strength fine-grain structural steels. This applies to both foundation and erection structures, like mobile or ship cranes. During the assembly of steel structures, unacceptable defects can occasionally be found in the weld area. In most cases, the economical solution would be local thermal gouging of the affected areas and re-welding. Due to the high shrinkage restraint of the joint groove in the overall structure, the superposition of global and local welding-induced stresses may lead to crack formation and component failure, particularly in interaction with the degradation of the microstructure and mechanical properties of high-strength steels during the repair process. However, manufacturers hardly have any information about these issues and there is a lack of recommendations and guidelines to take these safety-relevant aspects into account in adequate repair concepts. The aim of this research is to derive recommendations for repair concepts appropriate to the stresses and materials involved providing a basis for standards and guidelines to avoid cold cracking, damage and expensive reworking especially for high-strength steels. Part 1 of this study involves systematic investigations of influences of shrinkage restraint during repair welding of two high-strength steels S500MLO for offshore application and S960QL for mobile crane structures. The quantification of the shrinkage restraint of repair weld joints was achieved by means of experimental and numerical restraint intensity analysis. In welding experiments with self-restrained slot specimens, restraint intensity and introduction of hydrogen via the welding arc using anti spatter spray were varied systematically to analyse the effect on welding result, residual stresses and cold cracking. It could be shown that increasing restraint intensities result in significantly higher transverse residual stress levels. In the case of hydrogen introduction S500MLO showed no cold cracking independent of the restraint conditions. However, S960QL was found to be considerably cold cracking sensitive if hydrogen is introduced. With increasing restraint intensity length and number of cold cracks increases significantly. Part 2 [1] of this study is focussed on microstructure and residual stresses due to gouging and stress optimization via adequate heat control parameters in repair welding.