Laser-arc Hybrid Welding Research Articles

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.

Microstructure and Texture Characterization of Duplex Stainless Steel Joints Welded by Alternating Magnetic Field-Assisted Hybrid Laser-GMAW Welding.

In this study, 2205 duplex stainless steel with 12 mm thickness was welded by alternating magnetic field-assisted laser arc hybrid welding. The effect of an alternating magnetic field on the proportion distribution of two phases of the welded joint was investigated. The texture distribution, grain boundary misorientation, and grain size of welded joints were analyzed and characterized. The uniform distribution of alloying elements in the two phases was improved by a 20 mT alternating magnetic field. The diffusion dissolution of Ni and N elements into the γ phase was promoted, which was conducive to the transition from the α to γ phase and reduced the precipitation of Cr2N, such that the ratio of γ to α was 43.4:56.6. The ratio of the two phases of the weld was balanced by the alternating magnetic field of 30 mT, such that the ratio of γ and α was 44.6:55.4 and the texture dispersion was weakened. The Σ3 twinning boundary of the austenite phase in the weld was transformed to HABs, the ferrite phase underwent dynamic recrystallization, and the austenite phase had a cube texture, copper texture, and goss texture.

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.

Beam oscillating parameters on pore inhibition, recrystallization and grain boundary characteristics of laser-arc hybrid welded AZ31 magnesium alloy

Oscillating laser-arc hybrid welding of AZ31B magnesium alloy was carried out, the effects of beam oscillation parameters on pore inhibition, microstructure, grain boundary characteristics and tensile properties were investigated. The results showed that the pore formation can be inhibited with oscillating frequency higher than 75 Hz and radius smaller than 0.5 mm. The columnar grains neighboring the fusion line can be broken by the beam oscillation behavior, while the grain growth was promoted with the increase of frequency or radius. It should be noted that the coincidence site lattice (CSL) boundaries were mainly Σ13b and Σ29 boundaries, which were contributed by {101¯2} tensile twins and {112¯2} compression twins, respectively. The total fraction of CSL boundaries reached maximum at radius of 0.25 mm and frequency of 75 Hz, which was also confirmed as the optimized parameters. In this case, the elongation rate increased up to 13.2%, 12.8% higher than that of the weld without beam oscillation. Finally, the pore formation and inhibition mechanisms were illustrated according to the state of melt flow and keyhole formation, the abnormal growth was discussed basing on secondary recrystallization, and the relationship among the pore formation, grain size, boundary characteristics and weld toughness were finally established.

Effect of welding stability on process porosity in laser arc hybrid welding of dissimilar steel

Welding porosity is an important factor affecting the mechanical properties of welded joints. This study investigated the effect of welding stability on weld porosity to solve the problem of welding porosities in laser-arc hybrid welding of dissimilar steels. The type and formation mechanism of welding porosity were analyzed. The study results showed that the porosities generated during the welding process were process welding porosities. The generation of bubbles was closely related to the instability of the steam pressure inside laser keyhole. The droplet transfer form was an essential factor affecting the stability of the laser keyhole. When the droplet was in the projected transfer mode, the weld porosity could be effectively reduced. Penetration weld was also greatly helpful in reducing weld porosity.

CNTs distribution and ductility improvement mechanisms in oscillating laser-arc hybrid welding of AZ31B magnesium alloy

Oscillating laser-arc hybrid welding of AZ31B magnesium alloy with different content of carbon nanotubes (CNTs) was carried out, the distribution characteristics of CNTs and its effect on microstructure and tensile properties were investigated. The results showed that the CNTs can increase the absorption rate of the Mg alloy to the laser. Compared with the weld without CNTs, the grain sizes of the welds with CNTs were refined by more than 50 % and the maximum intensities of {0001} texture were weakened by more than 60 %. The mechanical properties of welds were mainly related to the distribution characteristics of CNTs. The tensile strength and elongation rate of the weld employing 3 wt% CNTs ethanol dispersion reached the maximum value of 244 MPa and 12.5 %. Finally, the distribution and ductility improvement mechanism of CNTs were discussed basing on the viscosity of molten pool and the bonding between the CNTs with the matrix.

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.

Microstructure homogeneity and mechanical properties of laser-arc hybrid welded AZ31B magnesium alloy

Laser-arc hybrid welding of AZ31B magnesium alloy was carried out, the effects of welding parameters on weld formation, microstructure homogeneity and mechanical properties were investigated. The results showed that laser-arc hybrid welding was beneficial to improve the weld formation of magnesium alloy by inhibiting the defect of undercut and pores. The weld microstructure was mainly columnar grains neighboring the fusion line and equiaxed grains at the weld center. It was interesting that the grain size at the upper arc zone was smaller than that at the lower laser zone, with the difference mainly affected by laser power rather than welding current and welding speed. The welding parameters were optimized as laser power of 3.5 kW, welding current of 100 A and welding speed of 1.5 m/min. In this case, the weld was free of undercut and pores, and the tensile strength and elongation rate reached 252 MPa and 11.2%, respectively. Finally, the microstructure homogeneity was illustrated according to the heat distribution, and the evolution law of tensile properties was discussed basing on the weld formation and microstructure characteristics.

Comparisons of laser and laser-arc hybrid welded carbon steel with beam oscillation

Laser welding and laser-arc hybrid welding of Q235 steel with and without beam oscillation were carried out, the weld formation, microstructure and mechanical properties were investigated. It was found that the width of the heat affected zone (HAZ) increased by beam oscillation during laser welding, while decreased during laser-arc hybrid welding. The side-plate ferrite (FS) increased by the beam oscillation, while the blocky ferrite (FB) was broken up and the proeutectoid ferrite (FP) was reduced. Moreover, the beam oscillation was beneficial to improve the elongation rate from 6.8% to 7.6% for laser welds and 8.3% to 9.8% for hybrid welds, while decrease the micro-hardness of the welds by 85 HV10 for the laser welds and 10 HV10 for the hybrid welds. Finally, the variation in width of HAZ was illustrated according to the heat distribution of the laser source, arc column and oscillating behavior of the laser beam. The relation between microstructure and mechanical properties was established, according to the stirring effect of the oscillated laser beam within the molten pool, and the solidification theories.

Laser-Arc Hybrid Cladding of Al-Mg Alloy Coating on AZ80 Mg Alloy: Effect of Laser Beam Oscillations Amplitude.

The effect of beam oscillating amplitude on the microstructure and performance of AZ80 Mg alloy cladded with Al-Mg alloy coating by laser–arc hybrid welding was studied. The penetration depth decreases significantly while welds are widened because of the increase in the oscillating area of a laser beam. Alloy segregation and keyhole-induced porosity can be suppressed by the laser beam oscillation. With the increase in the oscillating amplitude, the Al distribution becomes uniform in the weld seam because of the rapid and fierce stirring by the oscillating laser. However, the diluting of the cladded Al alloy restrains the formation of the brittle Mg17Al12 phase, and then causes the weakening of hardness and wear resistance of the cladded layer. Considered comprehensively, the optimized oscillating amplitude was 1 mm, which can produce the weld seam with good appearance, fewer segregation and porosity defects, and acceptable hardness and wear resistance.

Carbon emission modeling and mechanical properties of laser, arc and laser–arc hybrid welded aluminum alloy joints

Reducing environmental impact while achieving desired processing performance is increasingly sought after. Various welding processes are widely employed in advanced manufacturing, but their carbon emission characteristics vary. However, few studies have compared the carbon emissions of different welding methods. Therefore, it is urgent to analyze the carbon emission characteristics of commonly used welding methods, and to consider the welding performance for a comprehensive comparison. In this study, we construct the carbon emission models of three welding methods (laser, arc, and laser–arc hybrid welding) by building the monitoring platform. The characteristics and proportions of carbon emissions of each system in three welding methods are analyzed. Additionally, the bead morphology, microhardness, and microstructure of aluminum alloy joints are investigated to explain the results of tensile tests. The experimental results show that the appropriate welding heat inputs (WHI) of laser, arc, and laser–arc hybrid welding lead to the ultimate tensile strength (UTS) of 229.1 ± 2.6, 186.1 ± 3.0, and 250.0 ± 0.8 MPa, with the carbon emissions of 43.12, 26.06, and 120.25 g respectively. However, the carbon efficiency of laser–arc welding is lower than laser welding, while arc welding has the lowest carbon efficiency and the highest carbon emission. Increased welding speed can help reduce carbon emissions. For each welding method, properly penetrated joints have better tensile properties than joints with insufficient or excessive WHI, and too high WHI results in low carbon efficiency due to increased carbon emissions and decreased UTS. The welding process with lower WHI help to narrow the fusion zone (FZ) and heat affected zone, and refine the grains in the FZ. This study provides an empirical understanding on the relationship of welding method–carbon emission characteristic–mechanical property.

Plasticity improvement coupled by carbon nanotubes and beam oscillation in laser-arc hybrid welding of magnesium alloy

Laser-arc hybrid welding of AZ31B magnesium alloy was carried out employing carbon nanotubes (CNTs) and beam oscillation. The beam oscillation was beneficial to inhibit the easily occurred agglomeration of CNTs by stirring the molten pool, and thus improve the weld plasticity due to grain refinement effect of the dispersed CNTs.

Effect of Dynamic Preheating on the Thermal Behavior and Mechanical Properties of Laser-Welded Joints.

The high cooling rate and temperature gradient caused by the rapid heating and cooling characteristics of laser welding (LW) leads to excessive thermal stress and even cracks in welded joints. In order to solve these problems, a dynamic preheating method that uses hybrid laser arc welding to add an auxiliary heat source (arc) to LW was proposed. The finite element model was deployed to investigate the effect of dynamic preheating on the thermal behavior of LW. The accuracy of the heat transfer model was verified experimentally. Hardness and tensile testing of the welded joint were conducted. The results show that using the appropriate current leads to a significantly reduced cooling rate and temperature gradient, which are conducive to improving the hardness and mechanical properties of welded joints. The yield strength of welded joints with a 20 A current for dynamic preheating is increased from 477.0 to 564.3 MPa compared with that of LW. Therefore, the use of dynamic preheating to reduce the temperature gradient is helpful in reducing thermal stress and improving the tensile properties of the joint. These results can provide new ideas for welding processes.

Characteristics of Laser-arc Hybrid Welding and the Effect of Heat Input Ratio on Welded Joint Performance

Characteristics of Laser-arc Hybrid Welding and the Effect of Heat Input Ratio on Welded Joint Performance

Effect of preheating and preplaced filler wire on microstructure and toughness in laser-arc hybrid welding of thick steel

Acicular ferrite (AF) is the most important microstructural constituent to achieve high toughness at low temperatures in weld metal of steels. This is due to the relatively small grain size and large misorientation angles. AF is known to form at non-metallic inclusions (NMIs), but under high cooling rates, as in deep and narrow laser-arc hybrid welding (LAHW), this phenomenon is scarcely studied. In deep and narrow LAHW, insufficient transportation of filler wire to the root results in low amount of NMIs, thus bainite-martensite mainly forms due to fast cooling. In this work, a 45 mm thick high strength low alloy steel was welded by double-sided LAHW using different groove preparations. The effect of different cooling times on the microstructure in the weld metal and the heat-affected zone was studied. A low fraction of AF and high hardness were achieved in the root of weld metal when using standard LAHW. This was related to a rapid cooling time (Δt8/5 < 1.0 s) and a low population of NMIs due to lack of filler wire. Micro X-ray computed tomography revealed centerline solidification cracks and porosity. Two external methods were conducted to assist the formation of AF and to reduce hardness, base plate preheating and preplaced metal-cored filler wire into the weld groove prior to welding. Preheating reduced hardness and increased the AF fraction due to increased cooling time. In addition, preheating showed to mitigate porosity. Preplaced filler wire provided an enhanced population of NMIs in the root thus significantly increased the fraction of AF. It was found that the diameter and chemical composition of NMIs has a strong correlation with the cooling time Δt8/5. High impact toughness (> 35 J) was achieved at −50 °C by combining preheating and preplaced filler wire, and up to 45 % fraction content of AF was reached. However, many NMIs were still inactive due to a small diameter (< 200 nm) and unfavorable chemical composition related to the high cooling rate. The external methods had no influence on the occurrence of weld centerline cracks in the root, which will require further attention to secure mechanical properties and integrity.

Investigation on microstructure and impact toughness of simulated heat affected zone of high strength low alloy steels by laser-arc hybrid welding

The microstructure and impact toughness of the simulated heat affected zone (HAZ) of a high strength low alloy steels by laser-arc hybrid welding (LAHW) were investigated in this paper. Homogeneous simulated HAZ specimens with different grain sizes were prepared using the welding thermal simulating technique. Instrumented impact test was conducted to investigate the toughness of the simulated HAZ. Multi-scale sub-structure characterization of the simulated HAZ specimens was implemented by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back-scattered diffraction (EBSD). The instrumented impact test found that the peak temperature T M mainly affected the crack propagation process, the crack propagation energy E p decreased as the increase of T M , while the crack initiation energy E i barely changed, the decrease of crack stable energy E a led to the change of E p . The multi-scale sub-structure characterization showed that the prior austenite grain size (PAGS), packet width, block width both increased with the rise of T M . The block width was similar to the facet size in the crack unstable propagation zone of the simulated HAZ specimens. The block was the microstructure unit controlling the crack propagation process of the LAHW simulated HAZ specimens.

Microstructure and mechanical properties of spray formed 7055 aluminum alloy by fiber laser-arc hybrid welding

The spray formed 7055 aluminum alloy with 4.2mm thickness was welded by laser-arc hybrid heat source. The microstructures and properties of the welded joints are studied. The results show that the weld appearance is very full and the weld zone is primary composed of equiaxed crystals. Those equiaxed crystals morphology in different positions are also different, and only a small amount of columnar crystals are locally formed in the fusion zone. The average microhardness values of the weld zone and the heat affected zone are lower than that of the base metal, reaching 64% and 82% respectively. The average tensile strength of welded joints with as-welded state reaches 51% of the base metal. However, the tensile properties of the joints are significantly improved after the two-stage solution and aging heat treatment, and the average tensile strength can reach 515MPa, which was about 84% of the strength of the base metal.

Dynamic formation characteristics and mechanism of hybrid laser arc welding surface layer by Ni-based filler metal based on rotating laser induction

This study used a nickel-based filler metal to fabricate a surfacing layer on a low-carbon steel substrate by a hybrid welding process with a rotating laser and arc. The surfacing layer's weld formation was studied using optical microscopic observation (OM). The microstructure of the layers was studied by using the scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The arc, metal transfer, molten pool flow behaviors, and U–I characteristics during hybrid laser arc welding (HLAW) were analyzed using the arc analyzer and high-speed camera. The results show that a rotating laser improves the weld formation of gas metal arc welding (GMAW). The microstructure of the two surfacing layers consists of dendritic γ phase and a small amount of Laves and NbC phases. The high dilution rate of the HLAW surfacing layer results in relatively more Laves and fewer NbC phases. The arc length of HLAW is dynamically deflected with the rotation of the laser, which expands the arc action and heating area of the molten pool. The droplet transfer mode changed from globular transfer dominant in GMAW to the projected transfer dominant in HLAW. The location where the droplet transfer into the molten pool is dynamic changed, forming a multi-point impact on the molten pool. Combined with the deflected arc with the laser rotating laser, the HLAW has a broad and deep molten pool. Understanding the metal transfer behavior of Ni-based alloys in rotating laser-induced arc hybrid surfacing is of great significance for improving surfacing forming.

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.

Joining 30 mm Thick Shipbuilding Steel Plates EH36 Using a Process Combination of Hybrid Laser Arc Welding and Submerged Arc Welding

This article presents a cost-effective and reliable method for welding 30 mm thick sheets of shipbuilding steel EH36. The method proposes to perform butt welding in a two-run technique using hybrid laser arc welding (HLAW) and submerged arc welding (SAW). The HLAW is performed as a partial penetration weld with a penetration depth of approximately 25 mm. The SAW is carried out as a second run on the opposite side. With a SAW penetration depth of 8 mm, the weld cross-section is closed with the reliable intersection of both passes. The advantages of the proposed welding method are: no need for forming of the HLAW root; the SAW pass can effectively eliminate pores in the HLAW root; the high stability of the welding process regarding the preparation quality of the weld edges. Plasma cut edges can be welded without lack of fusion defects. The weld quality achieved is confirmed by destructive tests.