MATERIAL FOR HIGH-STRENGTH OIL WELL STEEL TUBE AND METHOD OF MANUFACTURING HIGH-STRENGTH OIL WELL STEEL TUBE USING THE MATERIAL

摘要

PROBLEM TO BE SOLVED: To provide a material for high-strength oil well steel tube excellent in SSC resistance and having suppressed change of strength depending on a tempering condition when made into a steel tube having YS satisfying 862 MPa or more and less than 963 MPa, and a method of manufacturing a high-strength oil well steel tube using the material.SOLUTION: There is provided a material for high-strength oil well steel tube having a composition containing, by mass%, C:0.20 to 0.50%, Si:0.05 to 0.40%, Mn:0.3 to 0.9%, P:0.015% or less, S:0.005% or less, Al:0.005 to 0.10%, N:0.006% or less, Cr:0.1 to 0.8%, Mo:0.1 to 2.0%, V:0.02 to 0.3%, Nb:0.001 to 0.04%, B:0.0003 to 0.0030%, O:0.0030% or less and the balance Fe with inevitable impurities and having Rockwell hardness HRC satisfying the (1) formula. 15.6×[%C]+29.2≤HRC60.5×[%C]+31.1 (1), where [%C] is mass% of C content.SELECTED DRAWING: None