STEEL MATERIAL SUITABLE FOR USE IN ACIDIC ENVIRONMENTS

摘要

A steel material that has a yield strength in a range of 965 to 1069 MPa (140 ksi grade) and also have excellent SSC resistance are provided. The steel material according to the present disclosure contains a chemical composition consisting of, in mass%, C: 0.20 to 0.50%, Si: 0.05 to 1.00%, Mn: 0.05 to 1.00%, P: 0.025% or less, S: 0.0100% or less, Al: 0.005 to 0.100%, Cr: 0.20 to 1.50%, Mo: 0.25 to 1.50%, Ti: 0.002 to 0.050%, B: 0.0001 to 0.0050%, N: 0.0100% or less and O: 0.0100% or less, with the balance being Fe and impurities. The steel material contains an amount of dissolved C within a range of 0.010 to 0.050 mass%. The steel material also has a yield strength within a range of 965 to 1069 MPa, and a yield ratio of the steel material is 90% or more.