| 摘要 |
Provided is a ferrite-based heat-resistant steel that achieves an improvement in creep rupture ductility in the long-term region without impairing creep strength. This ferrite-based heat-resistant steel has a chemical composition comprising, in mass%, 0.03-0.15% C, 0-0.8% Si, 0.1-0.8% Mn, 8.0-11.5% Cr, 0.2-1.5% Mo, (0.4-3.0% W), 0.1-0.4% V, 0.02-0.12% Nb, 0.02-0.08% N, and iron and inevitable impurities as the remainder, and has a tempered martensite microstructure, wherein, by an intermediate tempering heat treatment in a two-phase state wherein a portion of an austenite phase has undergone martensitic transformation, internal strain or internal stress introduced by the martensitic transformation is relaxed, and excellent creep rupture ductility is achieved, even when a load within the elastic limit at the temperature of use of a steel material made of said ferrite-based heat-resistant steel is applied. |
