2009 年 27 巻 2 号 p. 144s-148s
The effect of Ce addition on microcracking susceptibility in the multipass weld metal of alloy 690 was investigated in order to improve the microcracking susceptibility in it. The ductility-dip cracking susceptibility in the reheated weld metal could be greatly improved by adding 0.015-0.025mass%Ce to the weld metal. Conversely, the excessive Ce addition to the weld metal led to liquation and solidification cracking in the weld metal. Hot ductility of the weld metal at the cracking temperature was greatly improved by adding 0.01-0.03mass%Ce, implying that the ductility-dip cracking susceptibility was decreased as a result of the desegregation of impurity elements of P and S to grain boundaries due to the scavenging effect of Ce. The excessive Ce addition to the weld metal resulted in the liquation and solidification cracking attributed to the formation of liquefiable Ni-Ce intermetallic compound. The multipass welding test confirmed that microcracks in the multipass welds were completely prevented by using the filler metal added 0.032mass%Ce.
