Laser-arc Hybrid Welding Process Research Articles

Modeling of Yb:YAG Laser Beam Caustics and Thermal Phenomena in Laser-Arc Hybrid Welding Process with Phase Transformations in the Solid State.

This paper focuses on the mathematical and numerical modeling of the electric arc + laser beam welding (HLAW) process using an innovative model of the Yb:YAG laser heat source. Laser energy distribution is measured experimentally using a UFF100 analyzer. The results of experimental research, including the beam profile and energetic characteristics of an electric arc, are used in the model. The laser beam description is based on geostatistical kriging interpolation, whereas the electric arc is modeled using Goldak's distribution. Hybrid heat source models are used in numerical algorithms to analyze physical phenomena occurring in the laser-arc hybrid welding process. Thermal phenomena with fluid flow in the fusion zone (FZ) are described by continuum conservation equations. The kinetics of phase transformations in the solid state are determined using Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) equations. A continuous cooling transformation (CCT) diagram is determined using interpolation functions and experimental research. An experimental dilatometric analysis for the chosen cooling rates is performed to define the start and final temperatures as well as the start and final times of phase transformations. Computer simulations of butt-welding of S355 steel are executed to describe temperature and melted material velocity profiles. The predicted FZ and heat-affected zone (HAZ) are compared to cross-sections of hybrid welded joints, performed using different laser beam focusing. The obtained results confirm the significant influence of the power distribution of the heat source and the laser beam focusing point on the temperature distribution and the characteristic zones of the joint.

Development of laser-arc hybrid welding process of butt joint for bogie pipe crossbeam components

High-speed railway vehicle bogies are the main load-bearing components, which are welded together from steel plates and tubes. Butt joint and T-joint are the main types and the joint thickness is between 8–20mm. The stability of laser-arc hybrid welding (LAHW) process correlated strongly with keyhole behaviour. In this paper, the common quality defects in full penetration root pass by LAHW were analysed. Controlling the root gap is adopted to stabilize the keyhole, to improve the stability of weld quality. A novel type of butt joint with micro structure based on Y-shaped grooves has been designed, to meet both the requirement of controlling root gap and industrial large-scale batch production. Two new structure parameters, 2 mm of the remaining blunt edge thickness and 0.3 mm of the half width of root opening, were proved by the flat plates welding test. Finally, the joint with micro structure and the root pass welding parameters were transferred to the welding process of tube crossbeam components. The LAHW process verification was completed, and the test results showed the process meets the requirements of ISO 15614.

Defect monitoring of high-power laser-arc hybrid welding process based on an improved channel attention convolutional neural network

Defect monitoring of high-power laser-arc hybrid welding process based on an improved channel attention convolutional neural network

Stability analysis and porosity inhibition mechanism of oscillating laser-arc hybrid welding process for medium-thick plate TC4 titanium alloy

The influence of oscillating laser frequency and oscillation diameter on the stability and porosity of laser-arc hybrid welding of titanium alloys were investigated. The microstructure and basic mechanical properties of oscillating laser-arc hybrid welded joints were revealed. The results show that the oscillating laser significantly improved the macroscopic morphology of the joints, reducing the porosity from 5.48 % to 0.12 %. In the conventional laser-arc hybrid welding process, the number of keyhole surface closures was more and the time of droplet transition was longer, resulting in poor process stability. When the frequency was 150 Hz and the diameter was 1.5 mm at oscillating laser conditions, the number of keyhole closures within 200 ms was significantly reduced to 5 times compared to the conventional laser-arc hybrid welding (23 times). The droplet transition was stable, which resulted in a more stable hybrid welding process. In addition, after one oscillation cycle, the forward distance of the laser was relatively short, which can reopen the smaller pores generated in the previous cycle, leading to a significant reduction in porosity. When the frequency and diameter of oscillation decreased, the fluctuation for keyhole morphology was greater and the droplet transition was instability, resulting in an increase in porosity; When the oscillation increased, the fluctuation of the keyhole outer diameter was larger and the penetration depth decreased, which was not conducive to the welding of medium-thick plates. In the oscillating laser-arc hybrid welding process, columnar crystals in the middle of the molten pool grew towards the surface, reducing the segregation of impurities in the weld center. As a result, the elongation percentage of the joints was improved by 36.58 % compared to the conventional laser joints.

Review of Laser-Arc Hybrid Welding Process of Aluminum Alloys for New Energy Vehicles(Invited)

Review of Laser-Arc Hybrid Welding Process of Aluminum Alloys for New Energy Vehicles(Invited)

Fatigue behavior of 8 mm thick steel butt joints performed with hybrid laser arc welding

In the present research, the hybrid laser arc welding (HLAW) process has been applied to join 8 mm thick structural S355J2N steel under 1G configuration. Welding tests were performed at the Laser Welding Advanced Center available at the University of Cadiz, Spain. Different experimental welding parameters were fitted to obtain sound butt welds. The welds were subjected to different quality control tests, including visual inspection, metallographic characterization, microhardness measurements, and tensile and fatigue tests. The HLAW tests were performed at higher welding rates in 1G configuration than previously reported for 8 mm thick steels. Complete penetration was achieved in all welds, presenting suitable geometries without defects such as cracks, root humps, or porosities. Microhardness values measured at different welding zones were always below 350 HV. All welds broke at the base metal in the tensile tests. The present contribution reports novel fatigue results for these butt hybrid welds. The samples welded at the highest welding rate (2.5 m/min) were the ones providing the best fatigue response, due to the lower heat input applied under this condition.

Effect of laser-arc synergy on melting energy in laser-CMT hybrid welding of aluminum alloy

The physical process of laser-arc synergy in laser-cold metal transfer (CMT) hybrid welding of aluminum alloys is extremely complex and difficult to observe, which limits our understanding of laser-arc synergy and the industrial application of laser-CMT hybrid welding. In this paper, the laser-arc synergistic effect is studied quantitatively by the change of melting energy. Therefore, the dimensionless parameter (ψ) is introduced to discuss the effect of heat source guidance, energy distribution and distance of laser and arc (DLA) on melting energy increment. The results show that the novel laser-arc simultaneous co directional hybrid welding (no-guided) process increases ψ by 4.3 times and 1.8 times compared to CMT-guided and laser-guided processes, respectively. The laser-arc synergy is strongest when the laser power is 80% of the total power and DLA is 2 mm. The quantitative analysis method in this paper can be extended to the study of other hybrid heat sources, and this research can facilitate the optimization of the welding process and a better understanding of the hybrid welding mechanism.

Hybrid Laser-Arc Welding-Induced Distortion Analysis of Large-Scale Thin-Walled Cruise Ship Structures

Abstract In recent years, there has been increasing use of thin-walled structures with a plate thickness of 6–10 mm in the construction of cruise ships. As one of the important processes of cruise ship construction, hybrid laser-arc welding, combining the advantages of laser welding and arc welding, is increasingly applied in thin-walled cruise ships with the objective of reducing panel deformation. However, due to the weak stiffness of the thin-walled structure with a continuous weld length of 4–16 m, complex welding deformation, e.g., buckling deformation, will be prone to occur. This paper analyzed the deformation behavior of large-scale thin-walled cruise ship structures with the change of weld length, structural width, and plate thickness in the hybrid laser-arc welding process. The buckling mode induced by the welding deformation is predicted based on the combination method of thermal elastic–plastic and inherent strain, as well as experimental verification. By analyzing the deformation behavior with the weld length of 5–15 m, when the continuous weld length exceeds 7.5 m during butt welding of large thin-walled cruise ship structures, the welding deformation mode will change from bending deformation to buckling deformation, while the maximum deformation will be reduced by about 50%. Compared with the buckling mode of the traditional thick-walled structures, with the decrease of plate thickness, the buckling mode of large ship structures will change from wave buckling deformation of the whole structure to wave buckling at the edge of structures.

Microstructure evolution and mechanical properties in the depth direction of ultra-high power laser-arc hybrid weld joint of 316L stainless steel

Ultra-high power laser-arc hybrid welding (LAHW) provides a novel and effective method for joining thick-section with single-pass owing to the advantages of ultra-high penetration and efficiency. However, the evolution of microstructure and properties along penetration direction under ultra-high power LAHW (25 kW-level laser power) are still unclear. In this study, the distribution regularities of microstructure and properties in the depth direction of ultra-high power LAHW joint of 316L stainless steel are explored under the optimal weld formation. Results show that along the penetration direction, the cooling rate exhibits a significantly increasing trend by temperature field simulation. The macroscopic growth direction of δ dendrites changes from “Ʌ” to “→←” and “▪’’, and the microscopic dendrites changes from disordered coarse skeletal to directional fine skeletal and lathy morphology. Besides, the increase in cooling rate in the depth direction refines the grain size and reduces the texture composition types but increases the {001} 〈100〉 texture strength. Notably, “teardrop-like” boundary is formed in the lower layer and shrinkage cavities present in its central zone, the formation mechanism is investigated in detail. Finally, the tensile properties of joints in the depth direction exhibit a decreasing trend. The final fracture of the lower layer is in the weld center due to the existence of shrinkage cavities. This study points out the evolution of microstructure and mechanical properties in ultra-high power LAHW process, which provides a theoretical and experimental basis for regulating the performance of thick plates.

Effect of Hybrid Laser Arc Welding on the Microstructure and Mechanical and Fracture Properties of 316L Sheet Welded Joints

To explore the influence of different welding modes on the properties of 316L thin-plate welded joints, a new type of laser arc compound gun head similar to a coaxial one was used in this experiment. A high-speed camera was used to record the welding process and analyze the droplet splash behavior of the molten pool. The microstructure, microhardness change, and tensile test results of welded joints under different welding modes were analyzed. The results showed that laser welding (LW) is more prone to molten pool splash than hybrid laser arc welding (HLAW). The HLAW pool area was significantly increased compared with that of LW. The HLAW joint microstructure was more uniform than that of LW, which can improve the microhardness of welded joints. HLAW improved the tensile properties of the joint, with the maximum tensile strength of the joint increasing from 433 to 533 MPa. This test can provide guidance for the HLAW process.

Numerical simulation analysis of laser-arc hybrid welding of austenitic stainless steel

Laser-arc hybrid welding heat source has high energy density, and the temperature field is very uneven and unstable. It is impossible to systematically study the welding temperature field only through process tests. For this reason, the calculation of the thermal process of hybrid welding is of great significance to the systematic study of the temperature field of hybrid welding. In this paper, the laser-arc hybrid welding process of 8mm thick austenitic stainless steel was simulated by SYSWELD software. The results indicate that with the increase of laser energy, the melting time increases, and the peak temperature rises from 1,230°C to about 2,000°C; When the laser energy is 3.0 kW, the welding deformation reaches the minimum value of 0.68 mm, but the peak value of equivalent stress is high, which is 476.8193 MPa. When the arc voltage increases, the peak temperature rises from 1,650°C to 1,850°C, and the melting time increases. The arc voltage has little effect on the equivalent stress of the weld and has a clear impact on the welding deformation. When the voltage is 18 V, the maximum deformation reaches 2.191 mm.

Investigations on laser beam welding of thick steel plates using a high-power diode laser beam source

For joining of thick steel plates, commonly arc welding and partially laser-arc hybrid welding are used. Both techniques offer individual disadvantages besides their advantages. Arc welding processes are typically characterized by low welding speeds, high heat inputs, high distortions, and high filler material consumptions. Laser-arc hybrid welding processes are limited to weldable material thicknesses regarding weld imperfections as well as the ability to bridge gaps. Therefore, the investigations presented are about high-power diode laser beam welding of steel with plate thicknesses t between 15 and 30 mm using output powers PL of up to 60 kW and welding speeds v between 0.5 and 1.0 m/min. The welding experiments contain butt welds by using weld backing materials. Among other things, influence of energy per unit length (laser beam power PL, welding speed v), focal position z, and plate thickness t are analyzed for different reproducible processes. The evaluation of weld seams includes visual inspection, metallographic analyses regarding geometric characteristics, and weld imperfections as well as radiographic inspections. The investigations show achievable qualities and characteristics of the weld seams depending on the plate thickness t by using high-power diode laser beam sources. Weld seams on plates with thicknesses t of 15 and 22 mm were welded without cracks or other weld imperfections according to metallographic analyses and radiographic testing by using a laser beam power PL of 40 kW and the suitable process parameters developed. As a result, relatively high plate thicknesses t can be welded in a single layer with high quality as well as comparatively high welding speed v.

Effects of laser-arc hybrid welding on microstructure and mechanical properties of dissimilar steel joint

Laser-arc hybrid welding can improve production efficiency, and thus, it is being used in an increasing number of industries. Herein, the effects of laser-arc hybrid welding process parameters on the microstructure and mechanical properties of welded joint of low- and medium-carbon steels were investigated. Welding seam with best quality and no defects was obtained at welding current, arc voltage, laser power, and welding speed of 260 A, 24.8 V, 3300 W, and 0.8 m/min, respectively. Moreover, the enrichment of Mn in the weld zone promoted bainite formation. Rapid cooling led to the pseudo-eutectic phenomenon in the heat-affected zone (HAZ) on both sides of the weld; therefore, when an HAZ was closer to the weld on both sides, the pearlite content was higher. For low-carbon steel, the microstructure of the HAZ comprised ferrite, pearlite, and ferrite widmanstatten. For medium-carbon steel, the microstructure of the HAZ comprised a large amount of pearlite and a small amount of ferrite. In welded joint of both types of steels, differences in microstructure and internal stress altered the nanostructure morphology and distribution characteristics of cementite. The welded joint also had considerably better tensile strength due to a large number of dislocations and better grain refinement, which led to tensile fractures in the base metal zone of low-carbon steel. For a prefabricated weld notch, the tensile fracture mode was a ductile fracture with massive dimples.

Effect of liquid column on process stability and weld formation under ultra-high power fiber laser-arc hybrid welding of thick plates

Liquid column was a common problem in ultra-high power fiber laser-arc hybrid welding (UHLAHW) process, which has an adverse effect on the welding stability and weld formation. Hence, the influence of welding parameters on the behavior of liquid column was investigated systematically, including laser arc recombination process, laser power, and welding speed. As a result, the violent rising liquid column under laser was suppressed markedly after arc addition. However, it was hard to restrain liquid column upturn when laser power was extremely high, because the huge recoil pressure and shear force between metal vapor/plasma and molten pool could increase the upward momentum of melt. Besides, the height of liquid column and volume of spatters were directly influenced by welding speed, due to the welding line energy could significantly influence the flow of melt on the front of keyhole. By optimizing the welding process, the liquid column could be controlled, thereby significantly improving the welding process stability. Finally, a sound weld bead with qualified weld formation and 15.82-mm penetration was produced when the laser power was 21 kW and welding speed was 1.2 m/min under UHLAHW process. This work provides technical guidance for achieving stable welding process and qualified weld formation for thick plates.

Effect of the Cooling Rate of Thermal Simulation on the Microstructure and Mechanical Properties of Low-Carbon Bainite Steel by Laser-Arc Hybrid Welding

A new kind of low-carbon bainite steel with excellent strength and toughness was developed, serving as the bogie of the next-generation high-speed train. However, the softening of the heat-affected zone (HAZ) in laser-arc hybrid welding (LAHW) needs to be overcome. In this study, the effect of the cooling rate of the LAHW process on the microstructure and mechanical properties in the HAZ was explored via thermal simulation. The results showed that with increased cooling rate, the grain size increased, the content of lath martensite decreased, and the lath bainite gradually changed to a granular shape in the thermal simulation specimen. With the decrease in the cooling rate, i.e., with the increase of t8/5, the strength–toughness matching of the material showed a downward trend. The thermal simulation specimen with a t8/5 of 6~8 s had higher strength and good toughness, which can be considered a potential welding parameter reference. The content of martensitic austenite (M-A) constituents was the main factor that determined the strength and toughness of the joint. During the tensile test, the axial force caused the material to tighten, and the transverse stress as obvious in the part of the M-A constituents that are prone to microcracks and many defects, resulting in cracks, paths, and multi-component layers in the center. As a result, the thermal cycle specimens had mixed fracture characteristics.

Investigation of welding parameters effects on temperature field and structure field during laser-arc hybrid welding

Thermo-structural weak coupling model was adopted in numerical simulation of laser-arc hybrid T-joint welding. Gauss surface heat source and Rotary-Gauss body heat source were used to form a combined heat source in the temperature field analysis and simulate the arc and laser heat source. The laser-arc hybrid overlaying welding test of 304 stainless steel was carried out, and the weld molten pool morphology was obtained by metallographic corrosion test. The test results of a molten pool morphology show that the combination heat source can better simulate the laser-arc hybrid welding process. The effects of laser power, arc power and welding speed on residual stress and deformation of T-joint in laser-arc hybrid welding were studied by orthogonal experiments. Experimental results show that the arc power has great influence on the depth-width ratio, the laser power has great influence on the welding residual stress, and the welding speed has great influence on the thermal deformation. Through quantitative analysis and comparison, the optimal parameters were found during laser-arc hybrid welding.

Welding and Riveting Hybrid Bonding of 6061 Al and Carbon Fiber Reinforced Composites.

Welding and riveting hybrid bonding technology was applied to join 6061 aluminum alloy and carbon fiber reinforced plastics (CFRP). The laser-arc hybrid welding process and stepped rivets were used in the experiments to reduce the impact of the poor heat resistance of composites. The effect of hybrid welding arc current on the formation and mechanical properties of 6061 Al/CFRP joints was studied. Tensile shear load up to 4.65 kN was achieved by adjusting process parameters. The welding process and mode of the fracture were analyzed. The hybrid bonded joint obtained consisted of two parts: a welded joint of Al plate and Al rivet, and a bonded interface between Al plate and CFRP plate. The mechanical properties of the hybrid joint were mainly determined by the Al plate/Al rivet welded joint. The results of the study show that there are three interfacial bonding mechanisms between aluminum and CFRP. In addition to mechanical bonding between the Al plate and CFRP plate, there were also metallurgical bonding of Al-Mg intermetallic compounds with resin matrix and chemical reactions of aluminum with resin and carbon fibers at the interface, which could improve the mechanical properties of the joints.

Innovations in Monitoring, Control and Design of Laser and Laser-Arc Hybrid Welding Processes

With the rapid development of high power laser, laser welding has been widely used in many fields including manufacturing, metallurgy, automobile, biomedicine, electronics, aerospace etc. Because of its outstanding advantages, such as high energy density, small weld size, easy automation. Combining the two heat sources of laser and arc for welding can achieve excellent results due to the synergistic effect. Laser welding is a complicated physical and chemical metallurgical process, involving the laser beam and molten pool, keyholes and materials melting, evaporation and multiple physical process. Process monitoring and quality control are important content of research and development in the field of laser welding, which is the premise to obtain fine weld with high quality. Numerical simulation technology can describe many complex physical phenomena in welding process, which is very important to predict weld forming and quality and clarify the underline mechanism. In this paper, the research progress of process monitoring, quality control and autonomous intelligent design of laser and laser-arc hybrid welding based on numerical simulation were reviewed, and the research hotspots and development trends of laser welding in the future are predicted.

Double-sided Hybrid Laser-Arc Welding of 25 mm S690QL High Strength Steel

Hybrid Laser-Arc Welding (HLAW) technique is an enabler for the next generation high efficiency we lding, bu t in dustrial ad option ha s be en li mited du e to pr ocess complexity. Previously documented challenges with root cracks posed by incomplete penetration were significant; h owever, t his w ork p resents s uccessful w eld s amples p repared f rom S 690QL steel welded from two sides with a 16 kW disc laser. Weld travel speeds below 500 mm/min and weld line energies between 1.7 and 1.9 kJ/mm gave sound weld samples, evaluated for yield strength, elongation, hardness and Charpy-V toughness according to DS/EN ISO 10025-6:2004+A1. The results shown here indicate a significant i ncrease i n t he overall e fficiency of but t wel ds in high strength steels and further cement the HLAW process for high strength steels. It is shown that the consecutive nature of the weld procedure led to non-negligible interpass temperatures for the second weld.

Thermo-metallurgical simulation and performance evaluation of hybrid laser arc welding of chromium-molybdenum steel

The phase constitution of the joint had a significant effect on the mechanical properties of the welded components. In this study, a thermo-metallurgical finite element model was developed for the hybrid laser arc welding process to predict the phase field and melt-pool dimensions of double-sided butt-welded chromium-molybdenum steel plates. The good agreement of the predicted phase fields and melt-pool dimensions with experimental results showed the potential of the numerical model to guide process development for the hybrid laser arc welding process. Further investigation via the Vickers hardness test and the bending test was performed on the fabricated welds. Tensile test results demonstrated superior tensile properties in the fusion zone, where specimen failure occurred within the base metal region. Microstructure analyses revealed the strengthening of the fusion zone by the formation of the martensite phase and grain refinement at the heat-affected zone (HAZ). No failure or cracks were observed in the samples after the bend test, indicating the high quality of the weld. Analysis of the HAZ of the weld overlap region indicated a reduction in the hardness and martensite volume percentage.