LOW ALLOY HIGH STRENGTH SEAMLESS STEEL PIPE FOR OIL WELL EXCELLENT IN SULFIDE STRESS CORROSION CRACKING RESISTANCE AND PRODUCTION METHOD THEREOF, AND SELECTION METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a low alloy high strength seamless steel pipe having high strength with a yield strength of 110 ks level or more and excellent sulfide stress corrosion cracking resistance (SSC resistance) and a production method thereof.;SOLUTION: The low alloy high strength seamless steel pipe for an oil well excellent in sulfide stress cracking resistance is provided which has a composition containing, by mass%, C:0.15 to 0.50%, Si:0.8% or more, Mn:0.3 to 1.0%, P:0.012% or less, S:0.020% or less, Al:0.01 to 0.10%, N:0.01% or less, Cr:0.1 to 1.7%, Mo:0.4 to 1.2%, V:0.01 to 0.10%, Nb:0.01 to 0.08%, Ti:0.005 to 0.03% and B:0.0005 to 0.0030%. The steel pipe is produced by subjecting a steel pipe raw material having the same composition as that of the steel pipe to hot working thereby obtaining a seamless steel pipe, then subjecting the seamless steel pipe to hardening and tempering, so that percentage to all number of measurement points of hardness, of a measurement point with 1.6 or more of Mo segregation degree defined by C_Mo/(C_Mo)₀ where Mo concentration at each measurement point of a mapping analysis of Mo in an area exhibiting maximum hardness HRC_max of Rockwell hardness measurement points in a cross section orthogonal to a pipe axial direction of the steel pipe is 2.0% or less.;COPYRIGHT: (C)2016,JPO&INPIT