著者

東 司 田中 泰彦 石黒 徹

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.76, no.5, pp.783-790, 1990-05-01

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Grain refining behavior during austenitizing of 3.5%Ni-Cr-Mo-V turbine rotor shaft steel was investigated. Special attention was paid on the effect of Ni content and role of fine carbide precipitates on the austenite transformation and migration of the acicular austenite grain boundary. The microscopic observation of grain refining behavior reveals the following results. (1) The grain refining of 3.5%Ni-Cr-Mo-V steels during austenitizing occurs through two stages. The first stage is austenite transformation which γ-phases succeed to the acicular bainitic ferrite structure. The second stage is the formation of equiaxed grain at higher temperatures by the migration of grain boundary of the acicular austenite. (2) Driving force of the grain boundary migration in the second stage is considered to be the high density defects in the acicular austenite. (3) Increase of Ni content stabilize the acicular γ-phases up to higher temperatures. This decreases the formation of equiaxed grain due to the migration of acicular austenite grain boundary. (4) Increase of V content makes the grain refining difficult because the fine carbide precipitate such as VC works as a barrier against the grain boundary migration required for the formation of equiaxed grain.

著者

村田 純教 鷹見 恭平 神谷 美紗紀 森永 正彦 橋詰 良吉 三木 一宏 東 司 石黒 徹

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.88, no.4, pp.214-221, 2002-04

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In recent advanced high Cr ferritic steels, it is known that the Laves phase precipitates during creep test when the steels contain a relatively high level of Mo+W content. The Laves phase is believed to be granular in shape and to exist in the boundaries of lath, block, packet and prior austenite grains, but a number of fine Laves-phase precipitates are found to exist even inside the martensite lath in the tempered steels containing 10 mass% Cr and 4.6 mass% W. The shape of this Laves phase is plate-like, and the size is below 300 nm. The crystallographic relationship between the fine Laves phase and the matrix phase is as follows; (111)_<ferrite>//(001)_<Laves> and [01^^-1]_<ferrite>//[110]_<Laves>. In the microstruc ture aged at 923 K for 7〜14 Ms, the fine precipitates of the Laves phase disappear inside the martensite lath, and coagulated Laves phase is observed at the lath-, block-, or packet- boundaries. Only the low C steel containing 0.08% C and 3% W shows a few amounts of the fine precipitates of the Laves phase after aging at 923 K for 7.268 Ms. This compositional dependence of the precipitation behaviour can be understood qualitatively with the aid ofthe System-Free-Energy Concept.

著者

石黒 徹哉 髙田 正昭

出版者

日本租税研究協会

雑誌

租税研究 (ISSN:02880768)

巻号頁・発行日

no.756, pp.155-193, 2012-10