321 および 347 型鋼の長時間時効後の組織および機械的性質の変化

概要

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18-8 series stainless steels, which being used widely for big boiler plants recently, reveal some changes of mechanical properties during their use at high temperature, resulting from the changes of structures, i.e., precipitation of carbide particles and their coalescence. Type 321 and 347 stainless steels were aged for up to 10000 hr at approximate service temperature in use of 650℃. The changes of structure, especially, the changes of observed shapes of precipitated carbides, were examined by optical and electron microscopies and those of mechanical properties were also investigated. As results, precipitated carbides had many shapes, i.e., massive, fiborid, dendric, net-like and rod-like M_<23>C_6 and spheroidal TiC on the grain boundaries and fine spheroidal TiC, needle-like TiC and fine spherroidal M_<23>C_6 within the grains in type 321 steel, and also massive and spheroidal carbides (NbC) on the grain boundaries and spheroidal and massive carbides (M_<23>C_6+NbC), rosettes of NbC and needle-like carbide within the grains in type 347 steel. The Charpy impact value at room temperature and the creep-rupture strength at 650℃ of both steels became lower owing to long time aging.
社団法人日本鉄鋼協会の論文
1969-02-01