Microstructure, mechanical properties and residual stress of a 2205DSS/Q235 rapidly formed LBW joint

Welding seam (WS) of a 2205DSS/Q235 laser-beam welded (LBW) joint consisted of a martensitic phase and a small amount of residual austenite. The microstructure of the heat-affected zone (HAZ) of the 2205DSS side was ferrite-dominated. The HAZ of the Q235 side consisted of a coarse-grained zone (near the WS) and a fine-grained zone which was a result of the thermal cycling. The WS had the was highest hardness, and the hardness value of the HAZ was slightly higher than that of the respective base metal. The strength of these welding joints was approximately 460 MPa. The residual stress was investigated using a finite element method, hole-drilling method, and X-ray diffraction analysis. The results revealed two high stress regions on either side of the WS. The residual stress of the WS was relieved substantially because of the martensitic transformation at 400 °C.