Suppression of solidification cracking via thermal strain control in multi-beam welding

While conducting U-type hot-cracking tests on gas tungsten arc welding (GTAW) specimens, we irradiate the specimens with a laser beam (multi-beam welding) to prevent solidification cracking. To account for the observed suppression of solidification cracking, we calculate the thermal strain and high-temperature ductility curve using finite-element simulation and metallurgical analysis models, respectively. The high-temperature ductility curves do not exhibit any variation between the welding conditions because the temperature history of the molten pool is unchanged for all three welding scenarios considered. The GTAW thermal strain curve intersects with the high-temperature ductility curve, corresponding to the occurrence of cracking. However, in multi-beam welding, cracking is suppressed because of the relative decrease in thermal strain. The area of laser beam irradiation is larger because of the resulting decrease in yield strength. As a result, in multi-beam welding, the reduced specimen expansion leads to reduced stress loading on the weld bead, thereby preventing cracking because of the thermal strain decrease.