Wissenschaftliche Artikel der BAM
Filtern
Dokumenttyp
Schlagworte
- Laser beam welding (25)
- Additive manufacturing (23)
- Welding (14)
- Microstructure (11)
- Additive Manufacturing (10)
- Hydrogen (10)
- Mechanical properties (10)
- Laser powder bed fusion (9)
- Residual stress (9)
- Residual stresses (9)
- Solidification cracking (8)
- Friction (7)
- Tribology (7)
- Ultrasonic-assisted milling (7)
- Wear (7)
- Creep-resistant steel (6)
- Laser metal deposition (6)
- Process monitoring (6)
- Thermography (6)
- Fatigue (5)
- Resistance spot welding (5)
- Surface integrity (5)
- TIG welding (5)
- AFM (4)
- AISI 316L (4)
- Diffusible hydrogen (4)
- Hardness (4)
- Heat accumulation (4)
- High-strength steel (4)
- Hybrid laser arc welding (4)
- Hybrid laser-arc welding (4)
- L-PBF (4)
- Laser Powder Bed Fusion (4)
- Neutron diffraction (4)
- Numerical modeling (4)
- Selective laser melting (SLM) (4)
- Stress relief cracking (4)
- Thick-walled steel (4)
- AGIL (3)
- Alloy 36 (3)
- Artificial neural network (3)
- Atomic force microscopy (3)
- DED (3)
- Deep penetration (3)
- Fatigue crack propagation threshold (3)
- Fatigue tests (3)
- Heat treatment (3)
- High entropy alloy (3)
- Hydrogen embrittlement (3)
- In situ measurement (3)
- In situ monitoring (3)
- Inconel 718 (3)
- Infrared thermography (3)
- LIBS (3)
- Laser powder bed fusion (L-PBF) (3)
- Mechanical Engineering (3)
- Numerical modelling (3)
- Polymers (3)
- Post weld heat treatment (3)
- Quality assurance (3)
- Steel (3)
- Submerged arc welding (3)
- Ti-6Al-4V (3)
- Tubular X-joints (3)
- Varestraint test (3)
- Weld pool shape (3)
- 316L (2)
- AISI 304L (2)
- Additive manufacturing (AM) (2)
- Alloy modification (2)
- Austenite-to-martensite transformation (2)
- Bragg-edge imaging (2)
- Bulge effect (2)
- Chemical composition (2)
- Computed Tomography (2)
- Computed tomography (2)
- Contact resonance (2)
- Crack (2)
- Cracking (2)
- Critical strain (2)
- Crystallographic texture (2)
- Cyclic R-curve (2)
- Data preparation (2)
- Debye–Waller factor (2)
- Deuterium (2)
- Diffusion (2)
- Directed Energy Deposition (2)
- Distortion (2)
- EBSD (2)
- Electron backscattered diffraction (2)
- Finite element simulation (2)
- Force-distance curves (2)
- Fracture (2)
- Full penetration (2)
- GMA welding (2)
- Gap bridgeability (2)
- Gas metal arc welding (2)
- Gas tungsten arc welding (GTAW) (2)
- Grain refinement (2)
- Hardmetal (2)
- Heat control (2)
- High strength steels (2)
- High-entropy alloy (2)
- High-power laser beam welding (2)
- High-strength structural steel (2)
- Hot cracking (2)
- Hot stamping (2)
- Hydrogen Embrittlement (2)
- Hydrogen assisted cracking (2)
- Hydrogen-assisted cracking (2)
- Implant test (2)
- Inter layer time (2)
- LPBF (2)
- Laser beam melting (LBM) (2)
- Laser energy distribution (2)
- Laser hybrid welding (2)
- Laser-metal-deposition (2)
- Liquid metal embrittlement (2)
- Low transformation temperature (LTT) steel (2)
- Lubricants (2)
- Machining (2)
- Mechanics of Materials (2)
- Medium entropy alloy (2)
- Metals and Alloys (2)
- Microstructure characterization (2)
- Neutron imaging (2)
- Neutron radiography (2)
- Niobium carbide (2)
- Niobium carbide (NbC) (2)
- Numerical process simulation (2)
- Numerical simulation (2)
- Offshore (2)
- Optical flow (2)
- Pipeline steel (2)
- Plasma-transferred arc welding (2)
- Porosity (2)
- Post-weld heat treatment (2)
- Preheating (2)
- Ray tracing (2)
- Refill friction stir spot welding (2)
- Representative specimens (2)
- Residual Stress (2)
- Residual stress analysis (2)
- SSRT (2)
- Selective Laser Melting (2)
- Selective Laser Melting (SLM) (2)
- Simulation (2)
- Single pass welding (2)
- Software (2)
- Surface modification (2)
- Technical crack detection (2)
- Tensile properties (2)
- Texture (2)
- Thermal history (2)
- ToF-SIMS (2)
- Tool wear (2)
- Tribologie (2)
- WAAM (2)
- Weld pool dynamics (2)
- Wire arc additive manufacturing (2)
- X-ray diffraction (2)
- i-TRIBOMAT (2)
- 100Cr6 (AISI 52100) steel (1)
- 2101 duplex stainless steel (1)
- 3D Scanning (1)
- 3D printing (1)
- 9% Ni Steel (1)
- 9%Ni steel (1)
- AC magnetic field (1)
- AHSS (1)
- AM feature integration (1)
- ASTM E647 (1)
- Abdichtbauwerk (1)
- Accoustic emission (1)
- Additive Manufacturing (AM) (1)
- Additives (1)
- Advanced high strength steels (1)
- Advanced high-strength steel (1)
- Aging (1)
- AlMg0.7SiTiB filler wire (1)
- AlSi10Mg (1)
- AlSi10Mg alloy (1)
- Alite (1)
- Alkyd resin-based coating (1)
- Aluminum alloys (1)
- Aluminum bronze (1)
- Analytical calculation (1)
- Applications (1)
- Artificial Intelligence (1)
- Artificial intelligence (1)
- As-built LPBF IN718 alloy (1)
- Atomic force microscope (1)
- Austenitic stainless steels (1)
- Automated arc welding (1)
- Automated manufacturing (1)
- Automotive (1)
- Backlight (1)
- Bainitischer Schmiedestahl (1)
- Bauteilauslegung (1)
- Bayesian technique (1)
- Bead-on-plate welds (1)
- Beam oscillation (1)
- Bending test (1)
- Betriebsfestigkeit (1)
- Binders (1)
- Bismuth titanates (1)
- Bohrlochsonde (1)
- Bruchmechanik (1)
- Bulge formation (1)
- Bulging (1)
- Bulging effects (1)
- CFD model (1)
- Cantilever microprobe (1)
- Carbide (1)
- Carbon (1)
- Carbon dioxide footprint (1)
- Carbon steel (1)
- Catalysis (1)
- Cellular substructure (1)
- Cermet (1)
- Characterisation (1)
- Characterization (1)
- Characterization of corrosion layers (1)
- Charakterisierung (1)
- Charpy impact toughness (1)
- Chunky graphite (1)
- Cimensional Accuracy (1)
- Circumferential weld (1)
- Clinker substitute (1)
- Clustering (1)
- Co-Cr-alloy (1)
- Cobalt-chromium alloy (1)
- Cold cracking (1)
- Cold cracking safety (1)
- Columnar crystal growth (1)
- Component test (1)
- Component-like test (1)
- Composites (1)
- Computed tomography (CT) (1)
- Computer vision (1)
- Condensed Matter Physics (1)
- Condition monitoring (1)
- Convolutional neural network (1)
- Convolutional neural networks (CNN) (1)
- Core-shell structures (1)
- Corrosion (1)
- Crack closure effect (1)
- Crack-tip constraint (1)
- Creep (1)
- Creep behavior (1)
- Creep-resisting materials (1)
- Critical strain rate (1)
- Cryogenic steel (1)
- Cryogenic temperature (1)
- Crystal branch development (1)
- Crystal plasticity (1)
- Cutting forces (1)
- Cutting tool (1)
- Cyclic loading (1)
- Cylindrical turning (1)
- DED-EB (1)
- DED-arc (1)
- Damage prediction (1)
- Damage tolerance (1)
- Data evaluation methods (1)
- Data fusion (1)
- Data-driven quality assurance (1)
- Debye-Waller-Faktor (1)
- Deep learning (1)
- Deep penetration laser beam welding (1)
- Defect detection (1)
- Defects (1)
- Dental materials (1)
- Dichtungen (1)
- Diffraction (1)
- Diffraction-elastic constants (1)
- Diffusion/diffusivity (1)
- Digital Image Correlation (1)
- Digital image correlation (1)
- Digitalisation (1)
- Digitalization (1)
- Direct laser deposition (1)
- Directed energy deposition (1)
- Dislocation density (1)
- Dispersive XAS (1)
- Displacement (1)
- Dissimilar joints (1)
- Dissimilar materials (1)
- Dissimilar metal weld (1)
- Distortion upon baseplate removal (1)
- Ditigtal image correlation (1)
- Dual phase steel (1)
- Duplex AISI 2205 (1)
- Duplex stainless steel (1)
- Duplex stainless steels (1)
- Duplex steels (1)
- Dwell-time (1)
- EBAM (1)
- Edge quality (1)
- Effect of scanning strategies (1)
- Elastic modulus (1)
- Elastomers (1)
- Electrochemical permeation (1)
- Electromagnetic backing (1)
- Electromagnetic field (1)
- Electromagnetic forces (1)
- Electromagnetic stirring (1)
- Electromagnetic weld pool support (1)
- Electromagnetic weld pool support system (1)
- Electron backscatter diffraction (1)
- Electron beam welding (1)
- Electron microscopy (1)
- Element transport (1)
- Embedded electronics (1)
- Emisssivity (1)
- End crater (1)
- Endurance limit (1)
- Energy Engineering and Power Technology (1)
- Environmental conditions (1)
- Environmental impact categories (1)
- Error sources analysis (1)
- Evaporation (1)
- Experimental determination (1)
- Experimental procedure (1)
- FAIR data (1)
- FAT class (1)
- FEM (1)
- Fatigue Strength (1)
- Fatigue damage (1)
- Fatigue life (1)
- Fatigue limit (1)
- Fatigue properties (1)
- Femtosecond laser (1)
- Femtosecond laser processing (1)
- Ferritic spheroidal graphite cast iron (1)
- Ferroelectricity/ferroelectric materials (1)
- Filler material distribution (1)
- Filler wire (1)
- Filler wire mixing (1)
- Finish milling (1)
- Finite Element Method (1)
- Finite element (FE) (1)
- Finite element analysis (1)
- Finite element method (1)
- Finite element method (FEM) (1)
- Flange width (1)
- Flaw detection (1)
- Flüssigmetallinduzierte Rissbildung (1)
- Formation (1)
- Fractography (1)
- Fracture Mechanics (1)
- Frequency domain (1)
- Frequenzanalyse (1)
- Friction stir welding (1)
- Fuel Technology (1)
- Fusion zone size (1)
- Galvanized steel (1)
- General analytical solutions (1)
- Geteilte Infrastruktur (1)
- Green Deal (1)
- HAZ-softening (1)
- HCF (1)
- HSLA steel (1)
- Hard metals (1)
- Hardly separable problem (1)
- Harmonisation (1)
- Hastelloy X (1)
- Heat Treatment (1)
- Heat source models (1)
- Heat-affected zone (1)
- High power laser beam welding (1)
- High process speeds (1)
- High strength steel (1)
- High-entropy alloys (1)
- High-pressure hydrogen environment (1)
- High-strength filler metals (1)
- High-strength steel filler metal (1)
- High-strength steels (1)
- Hochfester Stahl (1)
- Hollow Specimen Technique (1)
- Hollow specimen (1)
- Hollow specimen technique (1)
- Hot Cracks (1)
- Hot cracking test (1)
- Hot tensile test (1)
- Hot working tool steel (1)
- Hybrid Laser arc Welding (1)
- Hybrid repair (1)
- Hydraulic reactivity (1)
- Hydrogen Transfer Film (1)
- Hydrogen diffusion (1)
- Hydrogen measurement (1)
- IBESS (1)
- IBESS Approach (1)
- IN 718 (1)
- IN725 (1)
- ISO 12108 (1)
- Image processing (1)
- Image registration (1)
- Impact Absorbed Energy (1)
- Implants (1)
- In situ (1)
- In-situ process monitoring (1)
- In-situ tensile test (1)
- Inconel 625 (1)
- Industrial and Manufacturing Engineering (1)
- Instumented indentation test (1)
- Integrated alignment features (1)
- Intelligent tribological material characterization (1)
- Intelligente tribologische Werkstoffcharakterisierung (1)
- Inter-layer time (1)
- Interoperability (1)
- Iron aluminide (1)
- Joining dissimilar materials (1)
- Joining technology (1)
- Kernel average misorientation (1)
- Keyhole collapse (1)
- Keyhole dynamics (1)
- Kitagawa-Takahashi diagram (1)
- L-PBF IN718 material (1)
- LCF (1)
- LIBS TIG welding (1)
- LMD (1)
- LTT Weld Filler Materials (1)
- LTT filler metal (1)
- LTT weld filler materials (1)
- Lab-to-field up-scaling (1)
- Lab-to-field upscaling (1)
- Lack-of-fusion (1)
- Lamé curves (1)
- Large-scale test (1)
- Laser Metal Deposition (LMD) (1)
- Laser Powder Bed Fusion (L-PBF) (1)
- Laser Powder Bed Fusion (LPBF) (1)
- Laser Powder Bed Fusion (PBF-LB/M, L-PBF) (1)
- Laser Welding (1)
- Laser beam melting (1)
- Laser cutting (1)
- Laser energy absorption (1)
- Laser implantation (1)
- Laser metal deposition (LMD) (1)
- Laser powder-based directed energy deposition (1)
- Laser welding (1)
- Laser-based additive manufacturing (1)
- Laser-induced oxide layer (1)
- Laser-induced periodic surface strctures (LIPSS) (1)
- Laser-induced periodic surface structures (LIPSS) (1)
- Laser-plasma hybrid (1)
- Lead-free ceramics (1)
- Life cycle assessment (1)
- Lifetime (1)
- Liquid Metal Embrittlement (1)
- Liquid phase sintering (1)
- Local Weld Geometry (1)
- Local critical strain (1)
- Local fatigue approaches (1)
- Local fatigue spproaches (1)
- Localized laser dispersing (1)
- Lorentz force (1)
- Lorentz forces (1)
- Low-cycle fatigue (1)
- L‐PBF (1)
- MVT (1)
- MWIR (1)
- Machine learning (1)
- Machine vision (1)
- Magnesium Alloy (1)
- Magnesium alloy (1)
- Magnetic bath support (1)
- Magnetic field (1)
- Martensite (1)
- Matching ferritic filler metal (1)
- Materials database (1)
- Mechanical anisotropy (1)
- Mechanical mismatching (1)
- Mechanical property (1)
- Melt pool depth (1)
- Melt pool dynamics (1)
- Metal (1)
- Metal mixing (1)
- Microalloying influences (1)
- Microbiologically influenced corrosion (1)
- Microcracking (1)
- Microfocus X-ray computer tomography (μCT) (1)
- Mild steels (1)
- Minimum Waiting Time (1)
- Mining head gear (1)
- Misalignment of edges (1)
- Model calibration (1)
- Model order reduction (1)
- Modellierung (1)
- Modelling studies (1)
- Modification of structural morphology (1)
- Molten pool (1)
- Multi-materials joining (1)
- Multi-physical modelling (1)
- Multi-principal element alloy (1)
- Multi-principal element alloys (1)
- Multiple principal element alloy (1)
- Multiple reflections (1)
- NIR (1)
- Nanotribology (1)
- Nanowear (1)
- Natural silver wires (1)
- Near-surface X-ray diffraction (1)
- Neutron Diffraction (1)
- Neutron and X-ray diffraction (1)
- Ni alloy (1)
- Ni-based austenitic filler metal (1)
- Nickel (1)
- Notch stress approach (1)
- Novel metrology (1)
- Numerical Simulation (1)
- Numerical investigation (1)
- Numerical welding simulations (1)
- Offshore steel grade (1)
- Online Process Monitoring (1)
- Online monitoring (1)
- Open science (1)
- Open source (1)
- Optical Tomography (1)
- Optical tomography (1)
- Oscillating ball-on-disc test (1)
- Oscillating magnetic field (1)
- Oscillating vapor plume (1)
- Oxidation (1)
- PBF-LB/M (1)
- PBF-LB/M/316L (1)
- Parabolic flight (1)
- Partial penetration (1)
- Particle transfer (1)
- Path planning (1)
- Peak stress method (1)
- Peak stress method (PSM) (1)
- Penetration depth (1)
- Periodic solidification pattern (1)
- Piezoresistive (1)
- Piezoresistive cantilever (1)
- Pipe weld preparation (1)
- Plasma cutting (1)
- Plasma-cut samples (1)
- Plasma-transferred-arc (1)
- Plastic deformation (1)
- Polymer (1)
- Polymere (1)
- Polyurethan (1)
- Position detection (1)
- Post Weld Heat Treatment (PWHT) (1)
- Potential drop technique (1)
- Potentiodynamic measurements (1)
- Ppreheating temperature (1)
- Precipitation hardening aluminum alloys (1)
- Pressure-dependent solubility (1)
- Prevention (1)
- Probabilistic assessment (1)
- Process chain (1)
- Process simulation (1)
- Projekt AGIL - Alterung additiv gefertigter metallischer Materialien und Komponenten (1)
- Proper generalized decomposition (1)
- Properties (1)
- Prostheses (1)
- Pulsed laser beam welding (1)
- Quality monitoring (1)
- Ray teacing (1)
- Ray-tracing methods (1)
- Reactor conditions (1)
- Reference data (1)
- Reference standards (1)
- Refraction (1)
- Renewable Energy, Sustainability and the Environment (1)
- Repair welding (1)
- Repair-welding (1)
- Research data management (1)
- Residual Stresses (1)
- Residual stress in AM (1)
- Residual stress state (1)
- Ripples (1)
- Rissbildung in Stahl (1)
- Roughness (1)
- S-N curve (1)
- S-Phase (1)
- SEM (1)
- SIMS (1)
- SLM printed plasma torch (1)
- SWIR (1)
- SWIR thermography (1)
- Sample random results (1)
- Scan strategy influence (1)
- Scanning kelvin probe force microscopy (1)
- Scattering (1)
- Schallemission (1)
- Seam geometry (1)
- Selective laser beam melting (1)
- Selektive-laser-melting (1)
- Shared infrastruture (1)
- Shear modulus (1)
- Ship building (1)
- Shipbuilding steel (1)
- Sicherheit (1)
- Single asperity (1)
- Single asperity contact (1)
- Single-pass welding (1)
- Sliding wear (1)
- Small-scale specimens (1)
- Solidification (1)
- Solubility (1)
- Spark plasma sintering (1)
- Stainless Steel (1)
- Stainless steel (1)
- Stainless steels (1)
- Staircase method (1)
- Statistical analysis (1)
- Steel and aluminium (1)
- Steelmaking slag (1)
- Stochastic sample functions (1)
- Strain fields prediction (1)
- Strain measurement (1)
- Strain-free lattice references (1)
- Strain-free lattice spacing (1)
- Stress Relief Cracking (SRC) (1)
- Stress balance (1)
- Stress balance condition (1)
- Structural stress approach (1)
- Structure analysis (1)
- Sub-oxide (1)
- Supermartensitic steel (1)
- Surface Integrity (1)
- Surface preparation (1)
- Surface processing (1)
- Surface structures (1)
- Synchrotron radiation (1)
- TEKKEN (1)
- Temperature (1)
- Temperature dependence (1)
- Tensile Strength (1)
- Tensile loading (1)
- Tensile resistance spot welding experiment (1)
- Tensile strength (1)
- Tensile testing (1)
- Thermal analysis (1)
- Thermal cycles (1)
- Thermodynamic modelling (1)
- Thermodynamic simulation (1)
- Thick materials (1)
- Thick plate welding (1)
- Thick-plate welding (1)
- Thick-walled (1)
- Titanium (1)
- Trapping (1)
- Tribo-Analytik (1)
- Tribo-analytics (1)
- Tungsten carbide (WC) (1)
- Two-dimensional solidification (1)
- Two-run welding technique (1)
- UV-blocker addition (1)
- Ultraschall-Echoverfahren (1)
- Ultraschall-Messtechnik (1)
- Ultrasonic Assisted Machining (1)
- Ultrasonic machining (1)
- Upscaling (1)
- V-notch impact toughness (1)
- Vaporization (1)
- Varestraint testing (1)
- Verschlussbauwerk (1)
- WRC 1992 diagram (1)
- Wear particles (1)
- Weathering tests (1)
- Weld metal cracking (1)
- Weld pool (1)
- Weldability (1)
- Welded Joints (1)
- Welded joint (1)
- Welded joints (1)
- Welding Simulation (1)
- Welding simulation (1)
- Welding thermal cycle (1)
- Weldx (1)
- Werkstoffdatenbank (1)
- White light interferometry (1)
- Widerstandspunktschweißen (1)
- Wind energy (1)
- Wire electron beam additive manufacturing (1)
- Wire feed laser beam welding (1)
- Wire-based additive manufacturing (1)
- X-ray Diffraction (1)
- X-ray and Neutron Diffraction (1)
- X-ray and neutron diffraction (1)
- X-ray computed tomography (XCT) (1)
- X-ray refraction (1)
- Young's modulus (1)
- Zero wear (1)
- Zerstörungsfreie Prüfung (1)
- Zink (1)
- contact resonance (1)
- infrared Thermography (1)
- µ-gravity (1)
- µCT (1)
- µCT-analysis (1)
- μCT-analysis (1)
Organisationseinheit der BAM
- 9 Komponentensicherheit (215) (entfernen)
Paper des Monats
- ja (9)
Steelmaking slag is a by-product of steel production, of which 4.5 Mt were produced in 2020 in Germany alone. It is mainly used in road construction, earthwork and hydraulic engineering. A smaller part is returned to the metallurgical cycle, used as fertiliser or landfilled.
With this use, iron oxides still contained in steelmaking slag are lost. In addition, the possibility of producing higher-grade products from steelmaking slag is foregone. In recent decades, many researchers have investigated the production of Portland cement clinker and crude iron from basic oxygen furnace slags (BOFS) via a reductive treatment. Carbothermal treatment of liquid BOFS causes a reduction of iron oxides to metallic iron, which separates from the mineral phase due to its higher density. Simultaneously, the chemical composition of the reduced slag is adapted to that of Portland cement clinker.
In this study, German BOFS was reduced in a small-scale electric arc furnace using petrol coke as a reducing agent. The resulting low-iron mineral product has a similar chemical composition to Portland cement clinker and was rich in the tricalcium silicate solid solution alite (Ca3SiO5). Based on its chemical and mineralogical composition, similar to that of Portland cement clinker, the reduced BOFS has the potential to react comparably. In our study, the reduced BOFS produced less hydration heat than OPC, and its hydraulic reaction was delayed. However, adding gypsum has shown to accelerate the hydration rate of the reduced BOFS compared to that known from the calcium silicates of Portland cement clinker.
Further research to improve the hydraulic properties of the reduced slag is essential. If successful, producing a hydraulic binder and crude iron from BOFS has economic and ecological benefits for both the cement and steel industries.
The effect of the oscillating metal vapor plume on the keyhole and molten pool behavior during the laser beam welding of AlMg3 aluminum alloys is investigated by experimental and numerical methods. The real-time height of the metal vapor plume is measured by high-speed camera observation. The obtained experimental results are used to evaluate the additional heating source and laser beam attenuation caused by the scattering and absorption based on the Beer–Lambert theory. Furthermore, the dynamic behavior of the metal vapor plume is incorporated into a 3D transient heat transfer and fluid flow model, coupled with the ray tracing method, for the laser beam welding of the AlMg3 alloy. It is found that additional heating resulting from the scattered and absorbed laser beam energy by the metal vapor plume significantly expands the shape of the molten pool on the top region. Moreover, the oscillating metal vapor plume caused the fluctuation of the high-temperature region in the molten pool. The probability of keyhole collapse at the bottom increases 17% due to the oscillating laser power induced by the laser beam attenuation. The internal interplay between the metal vapor plume, molten pool shape, and keyhole collapse is obtained. The developed model has been validated by experiments, which shows a good agreement.
The spatial laser energy absorption inside the keyhole is decisive for the dynamic molten pool behaviors and the resultant weld properties in high-power laser beam welding (LBW). In this paper, a numerical simulation of the LBW process, considering the 3D transient heat transfer, fluid flow, and keyhole dynamics, is implemented, in which the free surface is tracked by the volume-of-fluid algorithm. The underlying laser-material interactions, i.e., the multiple reflections and Fresnel absorption, are considered by an advanced ray-tracing method based on a localized level-set strategy and a temperature-dependent absorption coefficient. The laser energy absorption is analyzed from a time-averaged point of view for a better statistical representation. It is found for the first time that a significant drop in the time-averaged laser energy absorption occurs at the focus position of the laser beam and that the rest of the keyhole region has relatively homogeneous absorbed energy. This unique absorption pattern may lead to a certain keyhole instability and have a strong correlation with the detrimental bulging and narrowing phenomena in the molten pool. The influence of different focus positions of the laser beam on the keyhole dynamics and molten pool profile is also analyzed. The obtained numerical results are compared with experimental measurements to ensure the validity of the proposed model.
Liquid metal embrittlement (LME) cracking is a phenomenon observed during resistance spot welding (RSW) of zinccoated advanced highstrength steels (AHSS) in automotive manufacturing. In this study, severe cracks are observed at the edge of the sheet under reduced flange widths. These cracks, traversing the AHSS sheet, culminate at the edge with a width of approximately 1.2 mm.
Through combined numerical and experimental investigations, and material testing, these cracks are identified and validated as a new type of LME crack. The mechanism behind this crack formation is attributed to unique geometric conditions that, when compared to center welding, amplify radial material flow by ninefold to 0.87 mm. The resultant tangential tensile stresses approximate 760 MPa, which exceed the yield strength of the examined advanced highstrength steel (AHSS) under heightened temperature conditions, and when combined with liquid zinc, promote the formation of this new type of LME crack.
Effect of Tensile Loading and Temperature on the Hydrogen Solubility of Steels at High Gas Pressure
(2023)
The hydrogen solubility in ferritic and martensitic steels is affected by hydrostatic stress, pressure, and temperature. In general, compressive stresses decrease but tensile stresses increase the hydrogen solubility. This important aspect must be considered when qualifying materials for high‐pressure hydrogen applications (e.g., for pipelines or tanks) by using autoclave systems. In this work, a pressure equivalent for compensating the effect of compressive stresses on the hydrogen solubility inside of closed autoclaves is proposed to achieve solubilities that are equivalent to those in pipelines and tanks subjected to tensile stresses. Moreover, it is shown that the temperature effect becomes critical at low temperatures (e.g., under cryogenic conditions for storing liquid hydrogen). Trapping of hydrogen in the microstructure can increase the hydrogen solubility with decreasing temperature, having a solubility minimum at about room temperature. To demonstrate this effect, the generalized law of the hydrogen solubility is parameterized for different steels using measured contents of gaseous hydrogen. The constant parameter sets are verified and critically discussed with respect to the high‐pressure hydrogen experiments.
The capability to produce complexly and individually shaped metallic parts is one of the main advantages of the laser powder bed fusion (PBF LB/M) process. Development of material and machine specific process parameters is commonly based on results acquired from small cubic test coupons of about 10 mm edge length. Such cubes are usually used to conduct an optimization of process parameters to produce dense material. The parameters are then taken as the basis for the manufacturing of real part geometries. However, complex geometries go along with complex thermal histories during the manufacturing process, which can significantly differ from thermal conditions prevalent during the production of simply shaped test coupons. This may lead to unexpected and unpredicted local inhomogeneities of the microstructure and defect distribution in the final part and it is a root cause of reservations against the use of additive manufacturing for the production of safety relevant parts. In this study, the influence of changing thermal conditions on the resulting melt pool depth of 316L stainless steel specimens is demonstrated. A variation of thermo-graphically measured intrinsic preheating temperatures was triggered by an alteration of inter layer times and a variation of cross section areas of specimens for three distinct sets of process parameters. Correlations between the preheating temperature, the melt pool depth, and occurring defects were analyzed. The limited expressiveness of the results of small density cubes is revealed throughout the systematic investigation. Finally, a clear recommendation to consider thermal conditions in future process parameter optimizations is given.
This study was carried out to investigate the neutron transmission signal as a function of sample temperature during a welding process. A theoretical description that includes the Debye-Waller factor was used to describe the temperature influence on the neutron crosssections. Neutron imaging using a monochromatic beam helps to observe transmission variations related to the material temperature. In-situ neutron imaging of welding experiments show the distribution of the temperature in bulk steel samples. The performed finite element modelling of expected temperature distributions shows good agreement with the obtained experimental data.
AbstractLaser beam welding has become widely applied in many industrial fields in recent years. Solidification cracks remain one of the most common welding faults that can prevent a safe welded joint. In civil engineering, convolutional neural networks (CNNs) have been successfully used to detect cracks in roads and buildings by analysing images of the constructed objects. These cracks are found in static objects, whereas the generation of a welding crack is a dynamic process. Detecting the formation of cracks as early as possible is greatly important to ensure high welding quality. In this study, two end-to-end models based on long short-term memory and three-dimensional convolutional networks (3D-CNN) are proposed for automatic crack formation detection. To achieve maximum accuracy with minimal computational complexity, we progressively modify the model to find the optimal structure. The controlled tensile weldability test is conducted to generate long videos used for training and testing. The performance of the proposed models is compared with the classical neural network ResNet-18, which has been proven to be a good transfer learning model for crack detection. The results show that our models can detect the start time of crack formation earlier, while ResNet-18 only detects cracks during the propagation stage.
Hybrid laser-arc welding (HLAW) was applied for butt welding of 14.5 mm thick plates of ferritic cryogenic steel X8Ni9 containing 9% Ni, which is used for manufacturing storage and transport facilities of liquefied natural gas (LNG). The weld seam formation and the achievable metallurgical and mechanical properties of the hybrid welds were investigated experimentally for two types of filler wire, an austenitic wire dissimilar to the base metal (BM) and an experimentally produced matching ferritic wire. Safe penetration and uniform distribution of the austenitic filler metal in the narrow hybrid weld could only be achieved in the upper, arcdominated part of the weld. The pronounced heterogeneous distribution of the austenitic filler metal in the middle part and in the root area of the weld could not ensure sufficient notched impact toughness of the weld metal (WM). As a result, a decrease in the impact energy down to 17±3 J was observed, which is below the acceptance level of ≥34 J for cryogenic applications. In contrast, the use of a matching ferritic filler wire resulted in satisfactory impact energy of the hybrid welds of up to 134±52 J at the concerned cryogenic temperature of -196 °C. The obtained results contribute to an important and remarkable conversion in automated manufacturing of LNG facilities. In other words, the results will help to develop a new laser-based welding technology, where both quality and productivity are considered.The efficiency of the developed welding process has been demonstrated by manufacturing a prototype where a segment of the inner wall of large size LNG storage tank was constructed. In this concern, hybrid laser arc welding was conducted in both horizontal (2G) and vertical (3G) positions as a simulation to the actual onsite manufacturing. The prototype was fabricated twice where its quality was confirmed based on non-destructive and destructive examinations.
Welded joints show large variation of the weld toe geometry along the weld seam, which is one important reason for the comparably large scatter in fatigue life. Therefore, it is crucial to take the local geometry at the weld toe into account, to reduce the conservatism in fatigue assessment of welded joints. This study is based on the IBESS procedure for the calculation of the fatigue strength, whereby the evaluation of local geometrical parameters is carried out by means of 3D surface scans. The approach is validated against 26 fatigue test series. The fatigue life is in general overpredicted, whereas good agreement is achieved for high stress ratio (R = 0.5). A sensitivity analysis conducted with IBESS shows that weld toe radii ρ < 2 mm and flank angle α < 30° have a significant influence on the calculated fatigue strength. In contrast to this, no strong correlation between ρ and the fatigue strength was determined experimentally in this study.
Through experimental observation and auxiliary numerical simulation, this investigation studies the different types of grain refinement of 5754 aluminum alloy laser beam welding by applying a transverse oscillating magnetic field. Scanning electron microscope results have proved that the application of a magnetic field can reduce the average crystal branch width and increase its number. The interaction between the induced eddy current generated by the Seebeck effect and the applied external magnetic field produces a Lorentz force, which is important for the increase in the number of crystal branches. Based on the theory of dendrite fragmentation and the magnetic field-induced branches increment, the grain size reduction caused by the magnetic field is studied. Furthermore, the effects of the magnetic field are analyzed by combining a phase field method model and simulations of nucleation and grain growth. The grain distribution and average grain
size after welding verify the reliability of the model. In addition, the introduction of a magnetic field can increase the number of periodic three-dimensional solidification patterns. In the intersection of two periods of solidification patterns, the metal can be re-melted and then re-solidified, which prevents the grains, that have been solidified and formed previously, from further growth and generates some small cellular grains in the new fusion line. The magnetic field increases the building frequency of these solidification structures and thus promotes this kind of grain refinement.
The amount of absorbed energy in the keyhole as well as its spatial and temporal distribution is essential to model the laser beam welding process. The recoil pressure, which develops because of the evaporation process induced by the absorbed laser energy at the keyhole wall, is a key determining factor for the macroscopic flow of the molten metal in the weld pool during high-power laser beam welding. Consequently, a realistic implementation of the effect of laser radiation on the weld metal is crucial to obtain reliable and accurate simulation results. In this paper, we discuss manyfold different improvements on the laser-material interaction, namely, the ray tracing method, in the numerical simulation of the laser beam welding process. The first improvement relates to locating the exact reflection points in the ray tracing method using a so-called cosine condition in the determination algorithm for the intersection of reflected rays and the keyhole surface. A second correction refers to the numerical treatment of the Gaussian distribution of the laser beam, whose beam width is defined by a decay of the laser intensity by a factor of 1/e2, thus ignoring around 14% of the total laser beam energy. In the third step, the changes in the laser radiation distribution in the vertical direction were adapted by using different approximations for the converging and the diverging regions of the laser beam, thus mimicking the beam caustic. Finally, a virtual mesh refinement was adopted in the ray tracing routine. The obtained numerical results were validated with experimental measurements.
Fatigue tests were performed on the forged aluminum alloy EN AW-2618A in the T61 state. Different stress ratios (R = -1, R = 0.1) were selected to study the influence of mean stress on fatigue life. Two overaged states (10 h/230 ◦C, 1000 h/230 ◦C) were also tested to investigate the influence of overaging on fatigue life. Transmission electron microscopy (TEM) was used to characterize the precipitates (S-phase), which are mainly responsible for the strength of the alloy. A fractographic analysis was also performed to determine the failure mode. Overaging reduces the fatigue life compared to the T61 state. The longer the aging time, the lower the fatigue resistance. The reason is the decrease in (yield) strength, which correlates with the radius of the S-phase: the precipitate radius increases by a factor of approximately two for the overaged states compared to the initial state. The analysis of the fracture surfaces showed crack initiation occurs predominantly on the outer surface and is
associated with the primary phases.
AISI 2205 duplex stainless steel is used in a variety of industries, including the chemical and petrochemical industries. This is due to its high tensile strength combined with good ductility and corrosion resistance. However, in laser beam welding, these properties are negatively afected by the high cooling rates typical of the welding process. The resulting higher ferrrite content in the weld metal than in the base material leads to a reduction in the ductility and corrosion resistance of the welded joint. To overcome this problem, in this study, thick plates were coated by direct energy deposition (DED) prior to laser beam welding, whereas a duplex powder mixture containing a higher nickel concentration was used as a coating material. To improve the weld quality for the proposed two-step process, a method of additional material deposition instead of conventional tack weld was investigated. The resulting welded joints showed a well-balanced austenite to ferrite ratio and their properties and microstructure were verifed by metallographic analysis, electron backscatter difraction and Charpy impact testing. Using the standard ASTM G48 test method, it was found that the corrosion resistance of the welds was improved by a factor of four in average compared to the conventionally welded joints. The resulting properties, such as good ductility and corrosion resistance, of the welds with pre-coated edges showed good agreement with those of the base metal and confrmed the proposed two-step process as a promising alternative to the conventional approaches for welding thick duplex stainless steel plates.
In recent years, in addition to the commonly known wire-based processes of Directed Energy Deposition using lasers, a process variant using the electron beam has also developed to industrial market maturity. The process variant offers particular potential for processing highly conductive, reflective or oxidation-prone materials. However, for industrial usage, there is a lack of comprehensive data on performance, limitations and possible applications. The present study bridges the gap using the example of the high-strength aluminum bronze CuAl8Ni6. Multi-stage test welds are used to determine the limitations of the process and to draw conclusions about the suitability of the parameters for additive manufacturing. For this purpose, optimal ranges for energy input, possible welding speeds and the scalability of the process were investigated. Finally, additive test specimens in the form of cylinders and walls are produced, and the hardness profile, microstructure and mechanical properties are investigated. It is found that the material CuAl8Ni6 can be well processed using wire electron beam additive manufacturing. The microstructure is similar to a cast structure, the hardness profile over the height of the specimens is constant, and the tensile strength
and elongation at fracture values achieved the specification of the raw material.
A new simplified and effective method has been formalised to estimate the Constant Amplitude Fatigue Limit (CAFL) of stress-relieved steel welded joints subjected to uniaxial push–pull loading and failing from the weld toe. Starting from the sharp V-notch assumption of the NSIF approach and the cyclic R-curve of the material in the heat affected zone, the proposed method identifies the CAFL as threshold level of the local stress field at the V-notched weld toe in the uncracked configuration. Such threshold stress field assures the crack arrest at the V-notched weld toe, according to the cyclic R-curve analysis. The method has been validated against experimental results and proved effective for a straightforward assessment of the CAFL of welded joints, as the stable crack propagation analysis of classical fracture mechanics approaches can be avoided.
The application of anti-corrosion coated, high-strength steels in the automotive industry has increased in recent years. In combination with various zinc-based surface coatings, liquid metal embrittlement cracking can be observed in some of these materials. A high-quality, crack-free spot-welded joint is essential to realize the lightweight potential of the materials. In this work, the LME susceptibility of different coatings, which will be determined by the crack length and the occurrence rate, will be investigated using a welding under external load setup. The uncoated specimens did not show any LME. EG, GI and GA showed significantly less LME than ZM coatings. The latter coatings showed much larger crack lengths than the EG, GI and GA coatings. Furthermore, two mechanisms regarding the LME occurrence rate were observed: the occurrence of LME in zinc–magnesium coatings was theorized to be driven by the material properties of the coatings, whereas the occurrence of LME at EG, GI and GA samples was forced mainly by the application of the external tensile load.
In the experimental setup of this work, the materials were exposed to unusually high mechanical loads (up to 80% of their yield strength) to evoke LME cracks.
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.
This article reports temperature-dependent elastic properties (Young’s modulus, shear modulus) of three alloys measured by the dynamic resonance method. The alloys Ti-6Al-4V, Inconel IN718, and AISI 316 L were each investigated in a variant produced by an additive manufacturing processing route and by a conventional manufacturing processing route. The datasets include information on processing routes and parameters, heat treatments, grain size, specimen dimensions, and weight, as well as Young’s and shear modulus along with their measurement uncertainty. The process routes and methods are described in detail. The datasets were generated in an accredited testing lab, audited as BAM reference data, and are hosted in the open data repository Zenodo. Possible data usages include the verification of the correctness of the test setup via Young’s modulus comparison in low-cycle fatigue (LCF) or thermo-mechanical fatigue (TMF) testing campaigns, the design auf VHCF specimens and the use as input data for simulation purposes.