定電位二次電解法による 9Cr-1Mo 鋼中 Laves 相の形態分析

概要

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Based on the studies of electrochemical stability of precipitates in 9Cr-1Mo steels, a method for selective separation and state analysis of Laves phase was established. By use of this method, precipitation behavior of Laves phase and carbides was examined and the effect of Laves phase on the mechanical properties of this steel after long-time aging was studied. The results are summerized as follows. (1) Laves phase extracted from 9Cr-1Mo steel was electrochemically less stable than carbides (M_<23>C_6), and was selectively decomposed and separated from carbides by controlled-potential electrolysis at +0.8V vs. SCE in 10% acetylacetone-5%LiCl-methanol (secondary electrolysis). (2) The amount of Laves phase can be calculated from the total dissolved amount of Fe, Cr, Mo and Si after the secondary electrolysis. The amount of carbides (M as M_<23>C_6) can be analyzed from the total amount of Fe, Cr, and Mo in insoluble residues after the secondary electrolysis. (3) In the steels aged for 1000h, Laves phase was found at temperatures between 550 and 625℃, the amount was maximum at 600℃, and increased with aging. (4) Precipitation of Laves phase decreased the Charpy absorved energy of 9Cr-1Mo steel ; when precipitated 0.5mass% of Laves phase, about 120J of Charpy absorved energy decreased.
社団法人日本鉄鋼協会の論文
1992-09-01