オーステナイト系ステンレス鋼溶接継手部におけるＬＴＳ現象に関する解析的評価法 第一報 各種溶接継手部におけるＬＴＳ感受性とその評価

Abstract

Recently, it has been reported that sensitization in welded joints could be promoted remarkably in the range of lower temperature, in which region, sentization would be hardly indcued for solution heat treated materials. This phenomenon, known as LTS (Low Temperature Sensitization), is becoming a serious problem for operating all sort of reactors and pressure vessels in the high temperature condition. This would be caused by fine carbide nucleation which was induced in weld thermal cycle duration.In this paper, effects of weld thermal cycle on the susceptibility to LTS were discussed by unstable heat conduction analysis. The following properties became evident after examining the experimental results. The peak temperature in weld thermal cycles which could cause LTS in the post weld heat duration, was decreased gradually and LTS region was extended with the increase of weld heat input. And it was also recognized that the susceptibility to LTS in Type 304L was much lower than that in Type 304. According to welding method to imporve the resistance to LTS, application of water quenching welding method was very effective, because of preventing of the carbide nucleation by rapid cooling in weld thermal cycle duration.