Effect of heat dissipation on solidification cracking behaviour of austenitic stainless steel during gas tungsten arc welding

Abstract

During the U-type hot cracking test of gas tungsten arc welding (GTAW), the back side stainless steel was subjected to a continuous water flow (water-cooled GTAW) to prevent solidification cracking. The solidification cracking susceptibility was evaluated by electron backscatter diffraction and a finite element method. As the misorientation angle of the dendrite structure decreased due to the water-cooling process, the solid-liquid interface energy increased, making the liquation film unstable, and bridging occurred between the secondary dendrite arms. The increased heat dissipation resulted in the formation of highly ordered dendrites. Therefore, uniformity in the growth directions of columnar dendrites can be promoted. Furthermore, decreased critical coalescence undercooling reduced the residual liquation film stability and decreased stress concentration in the weld bead.