Method for producing a high Cr ferritic steel with excellent ductility and creep rupture strength

摘要

PURPOSE: To improve creep ructure strength and ductility by subjecting a high Cr ferritic steel, having a specific composition where the amounts of impurities are controlled, to specific final hot working, to specific cooling, and to respectively specified normalizing and final tempering. ;CONSTITUTION: At the time of applying final hot working to the steel having a composition which contains, by weight, 0.02-0.20% C, ≤1% Si, ≤1.5% Mn, ≤1% Ni, 8-14% Cr, 0.01-3% Mo, 0.1-0.3% V, 0.01-0.2% Nb, 0.001-0.1% N, 0.001-0.05% Al, and 0.01-3.5% Cu and further contains, if necessary, 0.01-3% W and/or 0.0001-0.02% B and where the contents of P, S, and O among impurities are regulated to ≤0.025%, ≤0.015%, and ≤0.015%, respectively, this steel is held at 1100-1250°C for ≥1min and worked at ≥1000°C at ≥15% draft. This steel is cooled at ≥1°C/min cooling rate, held at 700-850°C for ≥1min and successively at 1000-1150°C for ≥1min, and cooled at ≥1°C/min cooling rate to undergo normalizing. Further, the final tempering is done at 650-850°C.;COPYRIGHT: (C)1994,JPO&Japio