LOW ALLOY HIGH STRENGTH SEAMLESS STEEL PIPE FOR OIL WALL EXCELLENT IN SULFIDE STRESS CORROSION CRACK RESISTANCE AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method of a low alloy high strength seamless steel pipe for an oil wall excellent in high strength with yield strength of 110 Ks range and sulfide stress corrosion crack resistance under a sour environment.;SOLUTION: A steel raw material having a composition containing, by mass%, C:0.15 to 0.50%, Si:0.1 to 1.0%, Mn:0.3 to 1.0%, P:0.015% or less, S:0.005% or less, Al:0.01 to 0.10%, N:0.01% or less, Cr:0.8 to 1.7%, Mo:0.2 to 1.1%, V:0.01 to 0.12%, Nb:0.01 to 0.08%, B:0.0005 to 0.0030% is heated to 1200°C or less, supplied to piercing rolling and then drawing rolling with a cross section limitation rate of 40 to 60% in a temperature range of 1000°C or higher and 10 to 40% in a temperature range of less than 1000°C, cooled to a temperature of 300°C or less, then applied a hardening treatment which is heating to the Ac3 transformation point to 1000°C again and quick cooling, and a tempering treatment which is heating to a temperature of the Ac1 transformation point or less and tempering.;COPYRIGHT: (C)2014,JPO&INPIT