Abstract
Recently, it has been reported that sensitization in welded joints of austenitic stainlness steels could be promoted by post weld heat treatment at lower temperature region, where sensitization would be hardly induced for solution heat treated materials. This phenomenon is known as LTS (Low Temperature Sensitization), which becomes a serious problem for operating all sort of reactors and pressure vessels used in high temperature conditions. This LTS would be caused by the formation of nuclei of fine carbides which was induced by heat cycles during weldings. In this paper, effects of welding methods on the susceptibility to LTS were discussed. The following properties became evident through the experimental results. Type 304 steel was senistized in welding process in the case of large heat input welding. On the other hand, in the case of low heat input welding such as EBW, LTS was detected, even if it was not sensitized under as weld condition. These results suggested that it was difficult to prevent LTS only by controlling the weld heat inputs. In addition to that, the susceptibility of several type of austenitic stainless steels for LTS was studied. As the results, stabilized stainless steels were found to be almost immune for LTS.
