2017 Volume 35 Issue 2 Pages 13s-17s
Stress corrosion cracking (SCC) has recently been observed in Ni-based alloy welds in nuclear power plants, despite countermeasures to prevent it. In the repair welding, temper bead welding (TBW) is applicable when post weld heat treatment (PWHT) is difficult to carry out. In TBW, the welding process variables are appropriately controlled so that the thermal cycles of the subsequent passes provide the area hardened by previous passes with the temper effect, so the hardened area size and thermal cycle tempering parameter (TCTP) are very important. However, very few studies have discussed the quantitative relationships among the hardened area size, TCTP and the welding process variables. In this study, we conducted a combined weld bead surface profile and heat conduction analysis for simulating temper bead welding with Ni-based filler metal to SQV2A plate under various welding conditions. We quantified the hardened area size and TCTP as linear functions of the welding process variable parameter, which was derived from welding heat conduction theory with a moving heat source. Consequently, we concluded that the appropriate welding conditions in temper bead repair welding can be determined based on the welding process variable parameter.
