LOW ALLOY STEEL

摘要

A low alloy steel subjected to thermal treatment after welding, the low alloy steel containing, in mass%, 0.01 to 0.15% C, 3% or less Si, 3% or less Mn, 0.08% or less Al, and one or more element selected from among Ti, V and Nb in a range satisfying equation (1), the remainder being Fe and impurities, wherein the impurities contain 0.01% or less N, 0.05% or less P, 0.03% or less S, and 0.03% or less O. Said low alloy steel exhibits excellent resistance to embrittlement caused by hydrogen such as stress corrosion cracking in a wet hydrogen sulfide environment in a HAZ. Equation (1): 0.1×[C(%)]<=[Ti(%)]+[V(%)]+0.5×[Nb(%)]<=0.2. (Each element symbol in the equation represents the content (mass%) of each element.)