Solidification cracking prevention by thermal strain control via water-cooled gas tungsten arc welding

Abstract

During the U-type hot cracking test of gas tungsten arc welding (GTAW), water was flowed onto the back side of 310S stainless steel (water-cooled GTAW) to prevent solidification cracking. To investigate the prevention of solidification cracking, the relationship between the thermal strain curve and high temperature ductility curve was determined. A finite element simulation model was designed to obtain the thermal strain curve. The high-temperature ductility curve was obtained based on a combination of the solidification initiation and completion temperatures, in addition to the critical strain rate. The solidification initiation and completion temperatures were calculated using a supercooling model and segregation model, respectively. The critical strain rate was measured based on an in-situ observation method. The high-temperature ductility curves were constant under both welding conditions. The thermal strain curve of GTAW intersected the high-temperature ductility curve, thus resulting in solidification cracking. However, in the water-cooled GTAW, the decreased thermal strain curve did not intersect with the high-temperature ductility curve, and solidification cracking did not occur. In the water-cooled welding process, the thermal strain and stress of the weld bead decreased due to an increase in the yield strength.