Effect of Grain Size on Solidification Cracking Susceptibility of Type 347 Stainless Steel during Laser Welding

Abstract

In this study, the effect of grain size on solidification cracking susceptibility of Type 347 stainless steel was investigated by using U-type hot cracking test with developed in-situ observation method and the effect of grain size of the weld metal on critical strain for solidification cracking was evaluated quantitatively. The grain size of the weld metal varied from about 70 to 210μm by changing in the grain size of the base metal. Consequently, it was concluded that according to the measurement of CST (Critical Strain Temperature), solidification cracking susceptibility increased with an increase in grain size of weld metal. Moreover, the area of the grain boundary for each unit area decreased when the grain size increased, and then strain which was applied for grain boundary increased and then critical strain for solidification cracking of grain boundary decreased with grain size. Therefore, it was guessed that the solidification cracking susceptibility increased with an increase in grain size.