| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material superior in thermal cracking resistance, which can prevent initiation/propagation of thermal cracking even when subjected to an intense heat cycle, and can greatly prolong the life. SOLUTION: This steel material is characterized by including, by mass, 0.15-0.43% C, 0.2-1.0% Si, 0.5-2.0% Mn, 11.5-15.0% Cr, 0.9-4.0% (Ni+Co), 0.5-1.0% Mo, 0.05-0.50% Nb, 0.10-0.50% V, 0.3-1.0% W, and the balance Fe with unavoidable impurities; and having a mean crystal grain size of the observed old austenite of 5-50μm due to precipitated carbides, a fine martensite lath structure inside it, and a structure in which the micro carbides are dispersively precipitated in the martensite lath structure and the lath borders.
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