Arc characteristics in alternating magnetic field assisted narrow gap pulsed GTAW

Joining and welding is an essential component of manufacturing technology. New developments in joining and welding are evolved in order to acquire extraordinary benefits such as unique joint properties, synergistic mix of materials, cost reduction of component, increase productivity and quality, complex geometrical configurations, suitability and selection of material to manufacture new products. This chapter provides an update on recent developments of welding and joining to showcase above benefits. Theoretical background, process parameters, novel aspects, process capabilities, and process variants along with its application are presented in this chapter. Advanced welding and joining techniques are addressed under different headings of fastening and bonding processes, developments of arc welding processes, advanced beam welding techniques, sustainable welding processes, micro-nano joining and hybrid welding.

Advanced Joining and Welding Techniques: An Overview

In this study, the main defect, i.e., lack of fusion (LOF), occurring at the sidewalls in narrow gap laser-arc hybrid welding (NGHW) was confirmed to depend on the cross-sectional shape of previous pass, which was classified into four types, namely concave, convex, middle convex, and inclined shapes. Only the concave shape was effective in suppressing the LOF because the sharp corner between the weld and sidewalls could not be completely filled by next pass in the other three types. The effects of the welding parameters on the concave degree of weld cross-sectional shape were obtained from the dimensionless analysis related to the driving forces in the molten pool. It was found that the welding parameters, namely the arc current, welding speed, and groove width had a significant effect on the concave degree, whereas the laser power and laser-arc distance had no direct effect. A semi-quantitative criterion was proposed to predict the occurrence of the LOF. The LOF was suppressed when the ratio of the electromagnetic force to the liquid viscosity force was larger than 3.21 × 105, and the ratio of the surface tension gradient to the liquid viscosity force was larger than 1.28 × 104. The suppression mechanism of the LOF in NGHW was discussed in terms of the forces and melt flow in the molten pool.

Formation and suppression mechanism of lack of fusion in narrow gap laser-arc hybrid welding

Effects of groove parameters on space constraint of narrow gap laser-arc hybrid welding

Porosity suppressing and grain refining of narrow-gap rotating laser-MIG hybrid welding of 5A06 aluminum alloy

Laser arc hybrid welding became a useful method to weld thick plates. But a sound weld is not so easy to obtain because of the uncontrollability of droplet transfer state, especially in ultra-narrow gap welding process. In this study, V-like ultra-narrow gap welds were carried out using 80 % Ar + 20 % CO2 blend as shielding gas. A high-speed video system was used to observe the droplet transfer behaviors. The results showed that the transfer mode did not change with the same welding current. The transfer mode changed from the short circuiting transfer to the mixture of the short circuiting and the globular transfer and then to spray transfer as the welding current increased. The relationship between the droplet transfer process and the welded defects was studied to obtain high-quality weld joint with a stable transfer process. The optimal parameter window between welding current and groove size was found. Only when the welding current was 200 to 270 A and groove gap was 2 to 3 mm, can a good welded joint be got. Finally, 30-mm-thick plate with 5.49-mm maximum groove gap was welded well by one pass laser autogenous welding and seven passes laser arc hybrid welding process.

Ran Sun

Papers

A study of droplet transfer behavior in ultra-narrow gap laser arc hybrid welding