Laser-arc Hybrid Welding Research Articles

A pathway to mitigate macrosegregation of laser-arc hybrid Al-Si welds through beam oscillation

Macrosegregation is rather serious during laser-arc hybrid welding (LAHW) due to poor arc penetration ability. Here we presented a simple and effective method to improve solute transfer and mitigate macrosegregation by using beam oscillation. When oscillating amplitude A ≥0.8 mm and frequency f ≥ 300 Hz, the macrosegregation of the overall weld cross-section was 300% lower than that of the non-oscillation weld, and the longitudinal section reduced by 220%. The reduction of macrosegregation was attributed to the stirring and vortex suction effect produced by high-frequency oscillating beam, which improved turbulent flow and the convection of molten pool to homogenize the alloying elements of hybrid weld.

Microstructure and mechanical characterization of high strength low alloy steel welded joint by hybrid laser arc welding

Hybrid laser arc welding was developed to joint EQ70 steels. Welds with no visible defects were obtained. Investigations on microstructure and mechanical properties showed that: the welded metal (WM) consisted of acicular ferrite (AF), granular bainite (GB) and M-A constituents. The arc zone and laser zone possessed semblable HAZ microstructures. Coarse grained heat affected zone (CGHAZ) and fine grained HAZ (FGHAZ) were both composed of lath martensite (LM), GB and polygonal ferrite (PF). The intercritically HAZ (ICHAZ) consisted of martensite and M-A constituents. The microstructure of the subcritically HAZ (SCHAZ) was tempered sorbite. Partly cracked blocky M-A constituents were found at the grain boundary of intercritically reheated CGHAZ (ICCGHAZ). Some M-A constituents was slender and distributed in the grain of ICCGHAZ. The arc zone and laser zone had similar hardness and micro-shear strength distributions. The highest hardness and micro-shear strength of the backing and double-pass welded joints appeared near CGHAZs, reheated WM and ICCGHAZ. Slightly soften showed up at the SCHAZs. SCHAZ, CGHAZ and ICCGHAZ showed a reduction of micro-shear toughness. -40°C sub-size Charpy impact testing showed that FL specimens possessed the lowest impact values. The coarse CGHAZs and cracked blocky M-A constituents of ICCGHAZ may be the reason caused the toughness deterioration.

Numerical and experimental investigation of the formation mechanism and the distribution of the welding residual stress induced by the hybrid laser arc welding of AH36 steel in a butt joint configuration

Formation mechanism of the welding residual stress (WRS) is a key part of welding research. However, there is a lack of meaningful numerical models of the WRS. In this work, a thermal-metallurgical-mechanical (TMM) model was developed using SYSWELD to investigate the distribution and the formation mechanism of WRS during the hybrid laser arc welding of AH36 steel. A series of simulations were conducted to explore the effects of various factors on the WRS. The numerical results matched well with the experimental data. The computational accuracy was improved by considering the typical “wine glass” weld profile and the dilution rate during simulation. The evolution of the WRS is strongly affected by the interaction of phase transformation and strain hardening. The austenite-martensite transformation has a great potential to reduce the WRS whereas the austenite-bainite transformation produces high levels of WRS. The phase transformation temperature has a great influence on WRS.

Study on Application of Laser-Arc Hybrid Welding to Hull Construction Stage of General Merchant Ships

The application of advanced welding technologies is important for improving the efficiency of hull construction processes and reducing production costs. Laser-arc hybrid welding (LAHW) technology, which combines the advantages of laser and normal arc welding, is of high quality and is expected to improve productivity. However, there are some challenges in applying LAHW to the hull construction stage of general merchant ships, because the thickness of the main structural members is thicker than that of passenger ships and high-speed ships.

Fundamental plasma diagnostic study for guiding TIG arc phenomenon by laser beam irradiation

Laser-arc hybrid welding is divided into laser-based and arc-based welding. In the arc-based welding, the laser beam irradiation provides the guiding effect to the arc plasma. Some studies have repo...

Influence of Push and Pull Techniques on High-Speed Buried-Arc GMAW Process

Abstract: The GMAW torch orientation, whether pulling or pushing, influences both arc welding and hybrid processes. In hybrid laser-arc welding, for example, when the torch is pulled, a greater bead penetration is obtained. To promote greater penetration, the literature also indicates the use of a buried arc in GMAW, although it was initially developed to only operate with a vertically-positioned torch. Therefore, this work aims to investigate the influence of the push and pull techniques on the behavior of buried-arc GMAW at high welding speeds. Welds were performed with the push and pull techniques under the following conditions: buried and unburied (long) arc with welding speeds of 1.0, 1.5 and 2.0 m/min and current ranging from 450 to 470 A. The process tends to be more stable when pulling than when pushing (buried or long arc). Evidence of instability was only identified for the pushed buried arc, due to material accumulation at the front region of the molten pool, for the higher welding speeds. Only the 1.0 m/min buried-arc processes resulted in beads with an appropriate surface finish.

Hybrid laser-arc welding of thick-walled pipe segments with optimization of the end crater

The study deals with the application of the high-power hybrid-laser arc welding process on up to 15 mm thick pipe segments with the intention to avoid end crater imperfections during closing of the circumferential welds, where the pipes were turned during welding in 1G- and 2G-positions. Different techniques such as laser power ramp-down, abrupt switch-off of the laser power and change of the magnification of the laser spot diameter and defocusing of the laser beam relative to the workpiece were tested to remove the laser energy from the process. It could be shown that a high defocusing of the optic system above 40 mm with a resulting beam diameter > 2.9 mm in a short overlap length of approx. 20 mm leads to the formation of a cup-shaped weld seam, which is preferred for avoidance of cracks and pores in the end crater. A laser optics with motor-driven lens system was used for the welding experiments to defocuse the laser beam without changing the position of the arc.

Microstructure and mechanical properties of high strength TMCP steel hybrid disk laser-MAG welded joint

Hybrid laser-arc welding (HLAW) was carried out on high strength thermo-mechanical controlled process (TMCP) steel of 14 mm thickness using single-pass welding (SPW) and multi-pass welding (MPW) processes. Well-formed weld joints with good performance were successfully obtained. The results showed that the microstructure of weld was pre-eutectoid ferrite, acicular ferrite and some granular bainite. There were mainly lath bainite, granular bainite and acicular ferrite in the heat-affected zone. The grain sizes of SPW were thicker than MPW, and the bainite content of MPW was higher than SPW. The average hardness value of the fusion zone was lower than that of the Heat affected zone, but higher than that of the base material. The weld was divided into upper arc domain zone (ADZ) and lower laser domain zone (LDZ). The ADZ was harder than the LDZ. The average absorbed energy of SPW and MPW in the fusion zone at −40[Formula: see text]C was 125.5 and 92 J/cm2, respectively. The influences of microstructure on impact toughness were summarized by analyzing the hardness distribution and microstructure of the welded joint. The brittle transition temperatures of the two processes obtained by the energy criterion and the morphology criterion were close to each other.

Laser induced arc dynamics destabilization in laser-arc hybrid welding

The interaction between laser and arc plasma is a central issue in laser-arc hybrid welding. We report a new interaction phenomenon called laser destabilizing arc dynamics in kilowatt fiber laser-TIG hybrid welding of 316L stainless steel. We found the laser action significantly oscillates the arc tail with a 1–3 kHz high frequency. Direct numerical simulation demonstrates that the destabilization mechanism is due to the high-speed oscillated metal vapor ejecting from the mesoscopic keyhole. More interestingly, the high-speed metal vapor could contrict the arc plasma by physical shielding. This provides a fundamentally different explanation from the generally adopted metal vapor ionization theory for laser constrict arc plasma phenomenon. Also, the results substantiate that the arc plasma cannot easily enter into the keyhole because of the violent metal vapor.

Hydrogen embrittlement behavior of SUS301L-MT stainless steel laser-arc hybrid welded joint localized zones

Hydrogen induced stress corrosion cracking behavior of SUS301L-MT laser-arc hybrid welded (LAHW) joints has been investigated in our previous works. However, the hydrogen embrittlement (HE) behavior in each zone of this joint is still unclear. In this work, in combination with microstructures, cracks propagation paths and fracture surface morphologies analysis, in situ electrochemical hydrogen charging during slow strain rate tensile (SSRT) tests were performed on the specimens cut from base metal (BM), heat-affected zone (HAZ) and weld metal (WM) in SUS301L-MT stainless steel LAHW joints to investigate the HE behavior of each zone. The results indicated that deformation induced martensite transformation occurred in BM and HAZ specimens during SSRT tests, resulted in cleavage morphologies on the fracture center and dimples on other areas. The fracture surface of WM specimen was all covered with dimples. During in situ hydrogen charging, the cracks in BM and HAZ specimens initiated along αˊ/γ interface near the specimen edge. The cracks in WM specimen initiated along the δ-ferrites distributed at austenitic grain boundaries. After the cracks initiated, the hydrogen concentration distribution in combination with stress field at the front of cracks tips would induce the cracks propagation by “hydrogen enhanced local plastic deformation” and “hydrogen enhanced decohesion” mechanisms. As a result, mainly fracture characterizations of intergranular cracking, transgranular cleavage and secondary cracks formed on the fracture surface.

Effects of groove constraint space on plasma characteristics during Laser-MIG hybrid welding of Titanium alloy

Laser-MIG hybrid welding with groove shows great potential in thick plate joining. However, the plasma behaviors influenced by the groove space are not well understood. In this paper, special stair-stepping plates with groove were designed to form different groove configurations, and the effects of groove depth on the plasma characteristics were investigated systematically. The results showed that the plasma temperature decreased from 10,589 K to 8,527 K and the electron density increased from 1.30 × 1016 cm−3 to 1.44 × 1016 cm−3, when the groove depth increased from 0 to 20 mm. The reason may be that more laser-induced metal vapor, cooler than arc plasma, cannot leave the deeper groove space in time. The heat convection and radiation between the vapor and plasma resulted in the temperature decrease. Besides, as the groove constraint space increased, the plasma profile, frequency of droplet-transfer and weld width decreased, while the penetration depth increased to some extent. This research results would be inspirational and meaningful to the laser-arc hybrid welding of medium and thick plate.

Influence of welding angle on the weld morphology and porosity in laser-arc hybrid welding of AA2219 aluminum alloy

The influence of welding angle on weld morphologies and porosity characteristics was studied in laser-arc hybrid welding of AA2219 aluminum (Al) alloy. The upward sloping and vertical weld (USVW) was performed better than the downward sloping and vertical weld (DSVW). The high-speed camera was used to observe the welding process. It is found that the welding process becomes stable when the transitional position of the droplet was 2 mm away from the keyhole. By analyzing the force act on keyhole and characteristics of the pool, it is found that the weld morphologies and porosity characteristics were associated with gravity-laser angle (β), which affects the keyhole stability and characteristics of the pool. The results showed that the flow velocity was accelerated when the β increased, which was a benefit for decreasing porosity. This is because the gravity in the direction of the welding accelerates the pool flow. Due to the increasing of the β, the static pressure and the vapor pressure in the keyhole were increased, which improved the stability of the keyhole and decreased the porosity.

Cold Cracking Resistance of Butt Joints in High-Strength Steels with Different Welding Techniques

Investigation results are presented to improve the structural strength (cold crocking resistance) of weld joints in high-strength steels with the yield limit over 600 MPa. The effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and diffusion hydrogen saturation of build-up and fused base metals was experimentally studied. The diffusion hydrogen saturation of build-up (arc and hybrid welding) and fused (laser welding) metals was chromatographically examined. In gas-shielded arc welding, the diffusion hydrogen content in the fused base metal was shown to be limited to the concentration that does not exceed 0.4 ml/100 g due to an increase in the welding speed from 18 to 50 m/h. In laser and hybrid laser-arc welding of high-strength steels with the yield limit over 600 MPa, the diffusion hydrogen content in the fused metal makes up 0.07 and 0.2–0.3 ml/100 g, respectively, regardless of the welding speed. The cold cracking resistance was evaluated by a commonly accepted procedure of special reference butt samples. Optical and transmission microscopic studies permitted of revealing the effect of arc, laser, and hybrid laser-arc welding conditions on the weld metal structure and gaining detailed information on the dislocation density distribution. The relation between the level of local internal stresses and the structural factors of dislocation density distribution in the weld metal was established. In arc and laser welding, local internal stresses were shown to be reduced to the values that do not exceed 0.22 of the theoretical metal strength if the welding speed would make up 50 m/h. In hybrid laser-arc welding at 72–110 m/h, maximum local internal stresses are also less than 0.22 of the theoretical metal strength. An increase in the cold cracking resistance in butt weld joints of high-strength 14KhGN2MD and N-A-XTRA-70 steels was established to be reached due to a low concentration of diffusion hydrogen in fused metal and formation of the fine-grained structure of lower bainite with the uniform dislocation density distribution.

Особенности гибридной лазерно-дуговой сварки нержавеющей стали

Особенности гибридной лазерно-дуговой сварки нержавеющей стали

Peculiarities of hybrid laser-arc welding of stainless steel

Peculiarities of hybrid laser-arc welding of stainless steel

Modeling of Keyhole-Induced Pore Formation in Laser-Arc Hybrid Welding of Aluminum Alloy with a Horizontal Fillet Joint

A three-dimensional transient model is proposed to investigate the weld pool dynamic behavior in laser + metal inert gas (MIG) hybrid fillet welding of aluminum alloy in the horizontal position, which allows for the joint configuration and coupling of the keyhole, droplet and weld pool as well as the heat and mass exchange between gas and liquid phases and is able to simulate the temperature distribution, fluid flow and formation process of a keyhole-induced pore in hybrid welding with a horizontal fillet joint. The weld porosity is also measured using x-ray nondestructive testing technology. Keyhole behavior and the formation mechanism of keyhole-induced porosity were analyzed. The calculated results are in generally good agreement with the experimental ones. A clockwise vortex always exists at the middle part of the weld pool. The formation and growth of the molten metal bulge on the keyhole wall are responsible for the occurrence of a gas bubble, which has a variation in size and shape and can be split during welding. The keyhole collapses easily at its middle or upper part in horizontal fillet welding, and the capture of the bubble by the upper molten pool boundary enhances the possibility of porosity formation to some degree. The keyhole-induced pore is mainly formed at the regions near the keyhole bottom and the upper fusion line of the weld pool.

Microstructure and performance of hybrid laser-arc welded high-strength low alloy steel and austenitic stainless steel dissimilar joint

Effects of hybrid laser-arc welding process parameters on the weld formation of a dissimilar steel joint were studied. A full penetrated weld with minimum defects was obtained under the optimized parameters. Different thermal conductivities and phase transition temperature resulted in a wider heat affected zone (HAZ) of high-strength low alloy steel (EH36) than that of austenitic stainless steel (316L). Owing to the limited penetration of arc, the laser zone could be only heated by laser while the hybrid zone was heated by not only laser but also arc, resulting in higher heat input and larger grain size in hybrid zone than in laser zone. The addition of filler wire led to higher contents of chromium (Cr) and nickel (Ni) in hybrid zone than laser zone, which inhibited the formation of austenite and led to the formation of martensite in laser zone. Small grain size and existence of martensite resulted in higher hardness of laser zone than hybrid zone. Tensile samples of both laser zone and hybrid zone failed at the EH36 side with massive dimples distributing on the fracture surfaces, indicating good tensile property of the welds and typical characteristics of ductile fracture. Corrosion resistance of laser zone was weaker than that of hybrid zone, which was closely related to the formation of martensite with poor corrosion resistance instead of austenite with good corrosion resistance.

2016S-GS5-13 レーザ・アークハイブリッド溶接により製作された完全溶込みT継手に生じる溶接残留応力

2016S-GS5-13 レーザ・アークハイブリッド溶接により製作された完全溶込みT継手に生じる溶接残留応力

Mechanical Properties and Depth Penetration Optimization Using NSGA-III in Hybrid Laser Arc Welding

ABSTRACTHybrid welding is a process used in aeronautical materials to obtain benefits such as complete penetration, narrow heat affected zones, reduce filler material used, among others, mainly due the ability of the process to control filler-metal additions and heat input in materials such as steels, titanium and aluminum alloys. Recently a new industrial revolution is taken place called manufacturing 4.0, the aeronautical and automotive industry have a great interest in all the pillars which making it up, one of the principal pillars is the big data analysis such as welding parameters applied in advances welding processes. The present work describes a welding optimization applying non-dominated sorting genetic algorithm-III (NSGA-III) to find and predict depth penetration (DP) and mechanical properties, specifically ultimate tensile strength (UTS) in ASTM 1520 steel welded by a hybrid laser arc welding with the objective to improve the weld quality. A diverse experiment were used in order to obtain a suitable model, considering welding speed (WS), wire feed rate (WF), voltage (V), current (A) and laser power (P). The experimental results demonstrated that the pareto front values obtained by NSGA-III improve the DP and UTS. Microstructural phases and mechanical properties were discuss to complement the values obtained and chosen.

Effect of Quenching Tempering-Post Weld Heat Treatment on the Microstructure and Mechanical Properties of Laser-Arc Hybrid-Welded Boron Steel.

In the present study, we have investigated the effect of post-welding heat treatment (PWHT) of quenching and tempering (QT) on the microstructure and mechanical properties of welded boron steel joints processed using laser-arc hybrid welding on two commercial filler materials, SM80 (Type-I) and ZH120 (Type-II). The microstructure and mechanical properties of the weld joints were characterized via optical microscopy, Vickers microhardness, and the uniaxial tensile test. The macrostructure of the weld joint was composed of a fusion zone (FZ), heat-affected zone (HAZ), and base metal zone (BMZ). After the QT-PWHT, the QT specimens revealed the V-shape hardness distribution across the weld joint, while the as-welded specimen exhibited the M-shape hardness distribution. As a result, the QT specimens revealed the premature fracture with little reduction in the area at the interface between the HAZ and FZ, while the as-welded specimen exhibited the local necking and rupture in the BMZ. In addition, the Type-II filler material with a greater value of equivalent carbon content was rarely influenced by the tempering, maintaining its hardness in the as-quenched status, while the Type-I filler material showed a gradual decrease in hardness with the tempering time. The results demonstrate that the Type-II weld joint outperformed the Type-I weld joint in terms of the structural integrity of welded parts.