| 摘要 |
PROBLEM TO BE SOLVED: To provide high Cr ferritic heat resistant steel excellent in high temperature long time creep strength so as to withstand use in high temperature steam of >=625 deg.C and toughness. SOLUTION: This heat resistant steel has a composition containing <=0.12% C, <=1% Si, 0.05 to 1.5% Mn, <=0.03% P, <=0.015% S, 8 to 15% Cr, 0.2 to 3% Nb, <=4% Ta, one or two kinds of 0.02 to 4% W and 0.01 to 2.5% Mo, 0.001 to 0.1% N, 0.0001 to 0.01% B and 0.001 to 0.05% Al, if required, containing one or more kinds selected from Co, Ni, Cu, V, Nd and Ti, and the balance Fe with impurities, in which the contents of Nb, Ta, W and Mo also satisfy the following inequality (1), and the contents of Nb and Ta further satisfy the following inequality (2): 2.5×(Nb+1/2Ta)0.15-0.6×(Nb+1/2Ta)-(Mo+1/2 W)>; 0...(1), and Nb+1/2Ta<; 3.5...(2).
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