The steel for the oil well and production mannered null mass is superior in resistance sulfide stress corrosion crack Characteristic of the steel oil well casing which uses

摘要

PROBLEM TO BE SOLVED: To stably produce a high strength low alloy steel pipe for oil well use excellent in sulfide stress corrosion cracking resistance at a low cost.;SOLUTION: (1) This steel for oil well use has a composition containing 0.15 to 0.30% C, 0.05 to 1.0% Si, 0.10 to 1.0% Mn, ≤0.025% P, ≤0.005% S, 0.1 to 1.5% Cr, 0.1 to 1.0% Mo, 0.003 to 0.08% Al, ≤0.008% N, 0.0005 to 0.010% B and ≤0.008% Ca+O(oxygen) and moreover containing one or more kinds among 0.005 to 0.05% Ti, ≤0.05% Nb, ≤0.05% Zr and ≤0.30% V, and in which the properties of inclusions in the steel satisfy the following inequalities (a) and (b): the maximum length Lx≤80 μm...(a), and the number Kz of the ones with the grain sizes of ≥20 μm≤10 pieces/100 mm2...(b). (2) In the method for producing a steel pipe for oil well use, at the time of producing a steel pipe using the above steel, after tube making by hot working, without cooling, the pipe is directly quenched as it is, or is quenched after holding at a temperature of the Ac3 transformation point or more and is next tempered at the Ac1 transformation point or less.;COPYRIGHT: (C)2001,JPO