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Tandem laser-gas metal arc welding joining of 20a??mm thick super duplex stainless steel: An experimental and numerical study
摘要： The present work covers the topic of strains and stresses prediction in case of welded steel structures. Steel sheets of 20 mm thickness made in URTM2507Cu are welded using a laser and gas metal arc welding processes combination. The focused laser beam leads the arc in a Y-shape chamfer geometry. Both sources are 20 mm apart from each other in order to avoid any synergic effect with each other. In order to predict residual strain, a 3D unsteady numerical simulation has been developed in COMSOL finite element software. A volume heat source has been identified based on the temperature measurements made by 10 K-type thermocouples, implanted inside the workpiece. The 50 mm deep holes are drilled in the workpiece using dye-sinking Electrical Discharge Machining (EDM) machine. Before the implantation in the hole, each thermocouple is surrounded by Inconel sheathing. Hot junctions of the thermocouples are positioned in a way to feel two advancing molten pools. The equivalent heat source is composed of three sources. First one is a Goldak source that represents the molten pool induced by gas metal arc welding. The second one is a cylinder with an elliptic cross-section that represents the focused laser beam penetrating into the workpiece. The third one is a surface Gaussian source that represents energy radiated by arc and blocked by workpiece surface. Concerning mechanical simulation, an elasto-plastic behavior with isotropic hardening is implemented. A weak coupling is established between equations governing heat transfer and mechanics thanks to the temperature dependent coefficient of linear expansion. This numerical simulation made with some simplifying assumptions predicts an angular distortion and a longitudinal shrinkage of the welded structure. The numerical results are consistent with the displacements measured by digital image correlation method.
关键词： welding,simulation,Finite element method,materials processing,laser-gas metal arc welding,thermomechanics
更新于2025-09-23 15:19:57
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Atomic Diffusion Behavior and Interface Waveform on the Laser Shock Welding of Aluminum to Nickel
摘要： Atomic diffusion behavior and interface waveform characteristics and formation mechanism during laser shock welding were investigated by using a molecular dynamics (MD) model and smooth particle hydrodynamics (SPH) modeling. The MD simulation showed that the diffusion coef?cient of Al atom was larger than that of the Ni atom. Ni atom is easily diffused deeply into the Al lattice during impact welding. The SPH simulation showed that the wavelength and amplitude of the welding interface increased with loading speed, and SPH simulations at different loading speeds demonstrated that the movement direction of the Ni wave peak is the same as the welding direction, whereas the movement direction of the Al wave peak is opposite to the welding direction. The effective plastic strain and temperature were mainly distributed at the interface waveform. The shear stress of the composite and substrate foil is in opposite direction near the collision point, and the pressure near the collision point was as high as about 10 GPa. Energy-dispersive spectroscopy line scanning analysis showed the presence of a 2.5-lm-thick element diffusion layer at the wavy interface between Al and Ni, verifying the element diffusion between Al and Ni in the MD simulation.
关键词： laser shock welding,molecular dynamics,smoothed particle hydrodynamics,welding characteristics
更新于2025-09-23 15:19:57
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Effect of Laser Positioning on the Microstructure and Properties of NiTi-Copper Dissimilar Laser Welds
摘要： Dissimilar pulsed laser welding of 400-lm NiTi and Cu wires was used to investigate the effect of laser positioning on NiTi-Cu joint performance. Laser positioning was found to have a significant role in the microstructure due to the difference in mixing patterns and composition distributions. Homogenous element distribution was observed in both the NiTi offset and the centerline joints, while complex mixing patterns were observed in the Cu offset joints. Changing the laser position resulted in a change in alloy content in the weld pool that affected the mixing patterns, and the phases that were formed in the weld zone of each sample. By moving the laser beam from NiTi toward Cu, NiTi and NiTiCu in the weld zone were replaced by pure Cu which resulted in a decreased average hardness from 512 to 158 HV. However, high hardness values were found inside the weld zone of Cu offset welds due to the presence of hard and brittle ternary intermetallic compounds. The 100-lm Cu offset joint displayed the worst mechanical response due to its inhomogeneous microstructure and the presence of cracks and pores. It was shown that positioning the laser beam on the NiTi or on the centerline resulted in a better transition in microstructure that led to acceptable mechanical properties without optimizing laser parameters or inserting any interlayers.
关键词： dissimilar welding,copper,laser welding,laser positioning,shape-memory alloys,NiTi alloy
更新于2025-09-23 15:19:57
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Fatigue behavior improvements of laser-induction hybrid welded S690QL steel plates
摘要： In this paper, the improvements of fatigue performances of S690QL steel welded by laser-induction hybrid welding (LIHW) method were performed, mainly through the infrared imaging device to obtain the weld thermal cycle, fatigue machine to test the fatigue strength and scanning electron microscope to observe the fracture morphology. In fatigue tests, tension-tension fatigue loading and stress ratio R = 0.1 was selected. The LIHW fitted S-N curves were derived. It was found that the cracks with symmetrical grooves were initiated at the weld center (WC), while the single-laser welding (SLW) fatigue samples were fractured at the WC. However, the LIHW samples were finally fractured near heat-affected zone (HAZ). The fracture morphology of fatigue samples with stress amplitude of 108 MPa and 144 MPa were further selected to analysis. Due to different degree of defects or stress concentration, and different welding heat input absorption ability and cooling rate, in sudden fracture region, SLW fatigue samples mainly contained the brittle transient failure mode, LIHW fatigue samples mainly showed a ductile failure mode. It can thus be concluded that the LIHW method could improve the fatigue performance of S690QL steel joints.
关键词： Transient failure mode,Single-laser welding,Cracks,Laser-induction hybrid welding,Fatigue strength
更新于2025-09-23 15:19:57
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Microstructure and Corrosion Properties of Laser-Welded SAF 2507 Super Duplex Stainless Steel Joints
摘要： SAF 2507 super duplex stainless steel has been welded using laser beam (LB) welding and laser/gas metal arc hybrid (LGH) welding processes. The pitting and intergranular corrosion properties of the welding joints have been tested using electrochemical testing and microstructure observations. The volume fraction of the ferrite phase reaches 70% in the weld zone of the LB welding joint, while the volume fraction of the ferrite phase is 60% for the welding joint of LGH due to the introduction of Ni from welding wire. The pitting corrosion resistance of the welding joint for LB is better than that of LGH. The pitting corrosion is easily conceived in the heat-affected zone (HAZ) because of the formation of Cr2N in the HAZ during welding.
关键词： intergranular corrosion,pitting corrosion,super duplex stainless steel,laser-GMAW hybrid welding,laser beam welding
更新于2025-09-23 15:19:57
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Process studies on copper laser beam welding over gap by using disc laser at green wavelength
摘要： The increasing demand for the substitution of the internal combustion engine vehicles to the battery electric vehicles requires beside battery cells high performance power electronic devices such as power control units (PCU). However, a combined requirement of high junction temperature stability and a large joint area of the interconnection on the PCU is a challenge for the conventional joining method such as soldering and wire bonding process. The Laser Impulse Metal Bonding (LIMBO) process enables a high temperature stable weld joint and large joint area. During the LIMBO process only minimized thermal stress is induced into the underlying substrate by a spatial separation between both joining partners in an overlap configuration with a gap. Hence, an energetic separation between the melting and joining phase is given. In this paper, the LIMBO process is firstly investigated with the disc laser at wavelength λ = 515 nm. Due to the enhanced absorptivity of the laser beam at this wavelength on copper material, the process duration of the LIMBO process is about the half compared to the LIMBO process with wavelength λ = 1064 nm.
关键词： Shadow projection,Green laser beam,Heat conduction welding mode,Laser beam micro joining,LIMBO
更新于2025-09-23 15:19:57
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Experimental investigation on Ytterbium fiber laser butt welding of Inconel 625 and Duplex stainless steel 2205 thin sheets
摘要： In this study, welding of Superalloy Inconel 625 and duplex stainless steel 2205 (DSS 2205) has been successfully performed through Ytterbium fiber laser at different heat inputs. With decreasing energy input, width of the weld bead narrowed and the mechanical properties of the joint improved. Characterization of the weld joint was carried out using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and micro-hardness testing. No solidification cracks or porosity was observed in the microstructure of the weld metal (WM). Cellular dendritic and columnar dendritic grains were main grain types observed in the weld metal. At heat input of 43 J/mm, inter-dendritic arms of the weld metal witnessed more segregation of Molybdenum and Niobium in comparison of welded samples at heat input of 21.5 J/mm. Carbides of Cr, Mo and Ni are formed in the weld joint interface as revealed by the XRD analysis. Tensile strength study reveals the maximum strength of 890 MPa when the heat supplied is low i.e. 21.5 J/mm. This strength value is more than that of the base metal (DSS 2205). The result obtained in terms of comprehensive structure-property correlation, recommends the effectiveness of laser beam welding for joining of the said dissimilar alloys.
关键词： Mechanical properties,Laser beam welding,Duplex stainless steel 2205,Microstructure,Inconel 625
更新于2025-09-23 15:19:57
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Experimental and Numerical Simulation on Laser welding of High Manganese TWIP980 Steel
摘要： In this paper, the numerical simulation of laser tailoring process for the 2mm thickness TWIP980 steel sheet is carried out using Simufact welding software. The results show that the center of the laser welding heat source is small, and temperature is high. The front of the weld pool has a drop-shaped profile and a funnel-shaped cross section. The simulated weld joint has a high degree of conformity comparing to the actual weld joint. As the heat input (line energy) increases, the peak temperature of the thermal cycle and the weldment width increase. The simulated results indicate that the residual stress of the weld joint perpendicular to the weld along the surface is greater than that along the weld direction, and are both greater than the residual stress perpendicular to the weld along the thickness direction. The residual stress generated by welding is mainly concentrated in the direction perpendicular to the weld seam. With the heat input increase, the deformation after welding increases. For the studied TWIP980 steel, the recommending laser tailored blank (LTB) weld parameters are: power 3kW and welding speed 3m/min, which is the optimum welding process in the practical welding. The guiding significance of the software for laser welding simulation of TWIP980 steel was verified.
关键词： numerical simulation,laser welding,residual stress,temperature field,TWIP980 steel
更新于2025-09-23 15:19:57
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Filler metal distribution and processing stability in laser-arc hybrid welding of thick HSLA steel
摘要： Welds made by high power laser beam have deep and narrow geometry. Addition of filler wire by the arc source, forming the laser-arc hybrid welding (LAHW) process, is very important to obtain required mechanical properties. Distribution of molten wire throughout the entire weld depth is of concern since it tends to have low transportation ability to the root. Accurate identification of filler metal distribution is very challenging. Metal-cored wires can provide high density of non-metallic inclusions (NMIs) which are important for acicular ferrite nucleation. Accurate filler distribution can be recognized based on statistical characterization of NMIs in the weld. In the present study, it was found that the amount of filler metal decreased linearly towards the root. The filler metal tends to accumulate in the upper part of the weld and has a steep decrease at 45–55 % depth which also has wavy pattern based on longitudinal cuts. Substantial hardness variation in longitudinal direction was observed, where in the root values can reach > 300 HV. Excessive porosity was generated at 75 % depth due to unstable and turbulent melt flow based on morphology of prior austenite grains. The delicate balance of process parameters is important factor for both process stability and filler metal distribution.
关键词： Filler metal distribution,Microstructure,Thick steel,Non-metallic inclusions,High strength steel,Mechanical properties,Laser-arc hybrid welding
更新于2025-09-23 15:19:57
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Modelling and optimization of process parameters to obtain maximum tensile strength for laser butt welding of 316L austenitic stainless steel sheets
摘要： The attribute of high power density but low energy-input in Laser welding offers exciting solutions to the commonly encountered disadvantages with conventional joining techniques. In this paper, 316L Austenitic Stainless Steel metal sheets were butt welded using Nd:YAG Laser welding system. Owing to its low cost and specific properties such as excellent toughness, higher creep, stress to rupture at elevated temperatures, 316L A.S.S finds wide range of applications in the industrial arena especially in the automobile and marine sectors. Hence, it becomes imperative to examine its post weld properties after performing laser welding and find optimized values of the parameters. The prominent process parameters like Laser Power, Travel speed and Focal length were analysed and optimised. Design of experiment statistical tool was embraced for the systematic conduct of the tests. Response Surface Methodology (RSM) and analysis of variance (ANOVA) techniques were employed to identify the significant process parameters affecting the weld. An empherical relationship involving the parameters was developed to predict the ultimate tensile strength. The 3D response surface plot and contour plots were generated for this model to elucidate the interaction effect of Laser parameters (Travel speed and Focal length), (Laser Power and Focal Length) & (Laser Power and Travel Speed) on Ultimate Tensile Strength. The welded specimens cut by electric discharge machining were prepared for tensile testing as per the ASTM standard. The Universal Testing Machine was used to test the welded specimen. Microhardness Testing was also carried out on the base material and the Heat Affected Zone (HAZ) using Vickers Hardness Testing machine. The tensile tested specimens were used for metallurgical analysis using Scanning Electron Microscope (S.E.M.). Specimen prepared for metallurgical analysis were sectioned, mounted, ground and polished in accordance with recommended procedures in ASTM practice E 3-11. The metallurgical observations showed the existence of undulating topography of ductile fracture surfaces. The investigations reveals that the actual values of the Ultimate tensile strength of the weld were falling close with the predicted strength obtained through the proposed model. It can be concluded that the proposed model in this work can be utilised to predict tensile strength of the weld with more precision.
关键词： Design of Experiments,Ultimate tensile strength,316 L A.S.S,Response Surface Methodology (RSM),Nd:YAG Laser welding
更新于2025-09-23 15:19:57