0.4% 窒素を含有する高 Cr-高 Ni オーステナイト鋼におけるπ相の生成と組成

概要

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The microstructural change in a 25%Cr-28%Ni-0.4%N austenitic stainless steel during aging at 800℃ for up to 10000 h was studied by means of optical microscopy and lattice parameter measurement. A dichromium nitride, Cr_2N, precipitated at an carlier stage of aging both as intergranular precipitation and as cellular precipitation. Further aging caused π phase (a nitride with the structure of β-manganese type) precipitation, accompanied by redissolution of Cr_2N. A nitride transformation from Cr_2N to π phase started at 100 h and completed after 10000 h aging in solution specimens without prior cold deformation. Cold rolling prior to aging accelerated the nitride reaction. A coarse dispersion of Cr_2N produced by aging at 900℃ retarded considerably the nitride reaction at 800℃. The chemical composition of the π phase formed after 10000 h aging was determined to be Cr_<12>(Ni_<0.5>Fe_<0.4>Cr_<0.1>)_8N_4. The solubility of nitrogen corresponding to Cr_2N and π phase was 0.15 and 0.12_5 wt%, respectively, in this austenitic steel at 800℃.
社団法人日本鉄鋼協会の論文
1981-09-01