laser-GMA Hybrid Welding Research Articles

Application of robust prediction for a laser–GMA hybrid welding process and parameter optimization of 6061-T6 aluminium alloy

A methodology to predict and optimize the ultimate tensile strength of 6061-T6 aluminium (Al) alloy under a laser–GMA hybrid welding process is presented. Experiments were performed by changing welding process parameters. For the evaluation of weldability, the ultimate tensile strength in the weld zone was considered to be the most important criterion. In order to determine the optimum welding parameters, a robust regression analysis was performed to present a reliable prediction and a genetic algorithm was used. Based on the results of robust regression analysis and the genetic algorithm, the optimal process parameters were obtained. The ultimate tensile strength result obtained by the optimal parameters was much improved, when compared with that specified by the American Welding Society.

Duplex Stainless Steel for Bridges Construction: Comparison between SAW and Laser-GMA Hybrid Welding

Using duplex stainless steels for bridge decks would be a major step forward in providing durable, low maintenance structures, exploiting both their corrosion resistance and high mechanical properties, while fulfilling the required structural safety performances. In this work we investigated the possibility to replace the longitudinal welded joint between the deck plate and the girder trapezoidal stiffeners, performed by SAW, with a comparable one fabricated by hybrid laser welding (LB-GMAW). Potential advantages that could be achieved are, among others, productivity improvement, better detail fatigue resistance and lower distortion of the welded structure. The main differences obtained using SAW and LB-GMAW for the specific structural detail made in duplex stainless steel (UNS S32205) are presented. Technological, metallurgical features and weld integrity were mainly investigated. The utilization of the LB-GMAW technique resulted in welded joint fully penetrated, differently from the case of SAW, a higher productivity and reduced distortions. From a metallurgical point of view (i.e. austenite-ferrite phase balancing), results are still subjected to be improved but acceptable figures were already achieved.

레이저-GMA 하이브리드 용접에서 유동에 의한 기포 및 기공 형성 해석

Three-dimensional transient simulation of laser-GMA hybrid welding involving multiple physical phenomena is conducted neglecting the interaction effect of laser and arc heat sources. To reproduce the bubble and pore formations in welding process, a new bubble model is suggested and added to the established laser and arc welding models comprehending VOF, Gaussian laser and arc heat source, recoil pressure, arc pressure, electromagnetic force, surface tension, multiple reflection and Fresnel reflection models. Based on the models mentioned above, simulations of laser-GMA hybrid butt welding are carried out and besides the molten pool flow, top and back bead formations could be observed. In addition, the laser induced keyhole formation and bubble generation duo to keyhole collapse are investigated. The bubbles are ejected from the molten pool through its top and bottom regions. However, some of those are entrapped by solid-liquid interface and remained as pores. Those bubbles and pores are intensively generated when the absorption of laser power is largely reduced and consequently the full penetration changes to the partial penetration.

Application of grey relational analysis to determine welding parameters for Nd:YAG laser GMA hybrid welding of aluminium alloy

Grey relational analysis is carried out to develop a new approach for optimization of Nd:YAG laser and gas metal arc hybrid welding parameters. The qualities of a welded material depend on various welding parameters. The parameters chosen for the current study include wire type, shielding gas, laser power, laser focus, travelling speed and wire feedrate. The welding experiments are performed on 6K21-T4 Al alloy sheet which are mostly used in automotive industries. The ultimate tensile stress, the bead width, and the penetration are chosen as the criterion for optimising the welding parameters. The method based on an orthogonal array following Taguchi's recommendation is adopted in the present study. Based on the results of grey relational analysis, a set of optimal welding parameters are obtained. The results show that the optimal welding parameters determined by the grey relational analysis are much improved compared to those from the preliminary set of experimental parameters.

Fiber laser-GMA hybrid welding of commercially pure titanium

Fiber laser-gas metal arc (GMA) hybrid welding process was introduced to weld of commercially pure titanium (CP-Ti) of 1.5 mm in thickness. Effect of welding parameters on the hybrid weldability was investigated concerning the bead shape, hardness, tensile properties and microstructures of welded joints compared with those of a fiber laser welded joint. As a result, fiber laser-GMA hybrid welding process has been shown to weld of CP-Ti sheets in 1.5mm thickness at speeds of up to 9 m/min. In addition, fiber laser-GMA hybrid welding produces higher Vickers hardness and tensile strength than that of the base metal. Compared with the laser welded joints, it is obvious that the hybrid welded joints have better combination of strength and ductility.

Optimization of Laser-Arc Interspacing Distance during CO2 Laser-GMA Hybrid Welding by Using High-Speed Imaging

Laser welding has not easily been adopted in shipbuilding industry because of its poor gap bridging ability. Recently, laser-GMA hybrid welding process showed possibility to overcome the tight gap tolerance with improved productivity. The laser-arc hybrid welding process is inherently complex because it has three kinds of process parameters: arc welding, laser welding and hybrid welding parameters. In this study, welding phenomena were investigated to optimize the hybrid process parameter; interspacing distance between laser and arc. The bead surface and cross-sectional shapes were evaluated, and weld pool shape and droplet transfer were monitored by high speed camera to clarify welding phenomena.

Modeling of Weld Beads for Laser-GMA Hybrid Welding

For laser-GMA hybrid welds, the relationship between the process parameters and bead shapes was investigated by using the experimental design and the non-linear regression. The weld beads were fitted by two quadratic functions. By the statistical analysis, the primary bead was mainly affected by GMA welding parameters and the root bead was mainly by laser welding parameters. The root bead shaped deeper penetration and shallower width, as the laser power increased for the constant arc power. High laser power resulted in the martensite phase, therefore exhibiting the sudden increase of hardness as approached to the fusion line of the root bead.

Use of Synergistic Effects in High Power Laser-GMA Hybrid Welding for Manufacturing of Thick Walled Structural Pipes

In the manufacturing thick structural pipes recently a new process has been developed. This Paper describes this newly discovered process called Laser Hybrid welding. In laser hybrid welding two processes i.e. laser welding and Gas Metal Arc (GMA) welding are combined together to create synergistic effects. In laser GMA hybrid welding of plates with thicknesses of up to 20 mm, the problem of pore formation and of centre rib defects occurs frequently which have, up to now, not yet been subject to detailed scientific analysis. It was the objective of this research work to reduce these weld defects by weld parameter investigations (of a geometrical and also metallurgical nature) or to even avoid them completely. It was investigated to determine the extent to which shielding gas composition, (root) gap width and misalignment of the joining partners affect the techno-mechanical properties. For this purpose, the welds were subjected to non-destructive test methods (viz. visual inspections and X-ray examinations) and also to destructive test methods (viz. transverse sections hardness measurements, tensile tests and notch bending tests). The synergistic effects have been discussed in the light of the mechanical and metallurgical characterisations of the weldments. Optimum process parameters have been evolved which could tolerate up to 0.4mm root gap and 0.8mm of misalignment without causing any centreline cracking. Combinations of helium and argon gas shielding have been found to produce porous free welds. It has been concluded that it is possible to replace submerged arc welds by laser GMA hybrid welds in the manufacturing of longitudinally welded pipes.