1995 Volume 35 Issue 10 Pages 1232-1238
The variations of toughness of reheated weld metals were studied in the Pcm range of 0.13 to 0.20 mass%, using welding thermal cycle simulator. The reheating temperature dependence of toughness is quite different between weld metal of low Pcm and that of high Pcm. There is more remarkable toughness degradation in the range of 900 to 1000°C than that of 1200 to 1350°C in reheating of weld metals with high Pcm. The toughness degradation in 900 to 1000°C is characterized by Ti-B bearing weld metal with high Pcm. The toughness degradation of high Pcm weld metal in 1200 to 1350°C is not more remarkable than that of low Pcm such as Si-Mn weld metal. By increasing the Pcm, the toughness degradation in 900 to 1000°C is more intensified, and that in 1200 to 1350°C is more recovered. The following quantitative evaluation on the toughness degradation is conducted by microstructural analysis using Petch's relationship. The toughness degradation in reheating at 1000°C which is corresponding to be 72°C in Charpy impact transition temperature comes from the component of grain coarsening, about 46°C, and that of MA constituents, about 26°C. On the other hand, the toughness degradation in reheating at 1350°C, 32°C in Charpy impact transition temperature comes from the component of grain coarsening, about 11°C, and that of MA constituents, about 21°C.