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.

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

A study on process development of super-TIG welding for 9% nickel steel with Alloy 625

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 ERNiCr-3 butter layer on the microstructure and mechanical properties of API 5L X65/AISI304 dissimilar joint

Effects of post-weld heat treatment on dissimilar laser welded joints of austenitic stainless steel to low carbon steel

A comparative study on microstructure and mechanical properties near interface for dissimilar materials during conventional V-groove and narrow gap welding

Two types of welded joints were prepared using low alloy carbon steel and austenitic stainless steel as base materials In one variety, buttering material and weld metal were Inconel 82 In another type, buttering material and weld metal were Inconel 182 In case of Inconel 82, method of welding was GTAW For Inconel 182, welding was done by SMAW technique For one set of each joints after buttering, stress relief annealing was done at ~923 K (650 °C) for 90 minutes before further joining with weld metal Microstructural investigation and sub-size in situ tensile testing in scanning electron microscope were carried out for buttered–welded and buttered–stress relieved–welded specimens Adjacent to fusion boundary, heat-affected zone of low alloy steel consisted of ferrite–pearlite phase combination Immediately after fusion boundary in low alloy steel side, there was increase in matrix grain size Same trend was observed in the region of austenitic stainless steel that was close to fusion boundary between weld metal-stainless steel Close to interface between low alloy steel-buttering material, the region contained martensite, Type-I boundary and Type-II boundary Peak hardness was obtained close to fusion boundary between low alloy steel and buttering material In this respect, a minimum hardness was observed within buttering material The peak hardness was shifted toward buttering material after stress relief annealing During tensile testing no deformation occurred within low alloy steel and failure was completely through buttering material Crack initiated near fusion boundary between low alloy steel-buttering material for welded specimens and the same shifted away from fusion boundary for stress relieved annealed specimens This observation was at par with the characteristics of microhardness profile In as welded condition, joints fabricated with Inconel 82 exhibited superior bond strength than the weld produced with Inconel 182 Stress relief annealing reduced the strength of transition joints and the reduction was maximum for specimen welded with Inconel 82

R Nivas

Papers

A comparative study on microstructure and mechanical properties near interface for dissimilar materials during conventional V-groove and narrow gap welding

Effect of Stress Relief Annealing on Microstructure & Mechanical Properties of Welded Joints Between Low Alloy Carbon Steel and Stainless Steel