HIGH-TOUGHNESS STEEL FOR VESSEL FOR HIGH-TEMPERATURE AND HIGH-PRESSURE SERVICE EXCELLENT IN STRENGTH AT HIGH TEMPERATURE AND SR CRACKING RESISTANCE

摘要

PURPOSE:To obtain a high-toughness steel for vessels for high-temp. and high- pressure service excellent in strength at high temp. and SR cracking resistance by providing a composition containing, as principal components, C, Si, Mn, P, S, Mo, SolAl, Cr, V, B, T, N and Fe and by limiting the composition. CONSTITUTION:The high-toughness steel for vessels for high-temp. and high- pressure service excellent in strength at high temp. and SR cracking resistance can be obtained by providing a composition containing, by weight, 0.07-0.20% C, 0.12-1.00% Si, 0.7-1.8% Mn, =0.020% P, =0.010% S, 0.35-0.70% Mo, 0.020-0.05% SolAl, 0.10-0.40% Cr, 0.01-0.02% V, 0.0003-0.0015% B, =40ppm T and =40ppm N, as principal components, satisfying (2P+S)=[0.07-0.05(Cr+10V)]%, further containing, if necessary, one or more among 0.05-1.00% Ni, 0.05-0.30% C and 0.003-0.05% Nb and having the balance consisting of Fe and inevitable impurities.