LOW-ALLOY STEEL FOR PIPE FOR OIL WELL AND METHOD FOR PRODUCTION OF PIPE FOR OIL WELL FROM LOW-ALLOY STEEL Russian patent published in 2018 - IPC C22C38/26 C21D8/10 C21D9/08 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to low-alloyed steel for a pipe used in an oil well. Steel has the following chemical composition, in wt %: C: more than 0.45 and up to 0.65; Si: 0.05 to 0.50; Mn: 0.10 to 1.00; P: up to 0.020; S: up to 0.0020; Cu: up to 0.1; Cr: 0.40 to 1.50; Ni: up to 0.1; Mo: 0.50 to 2.50; Ti: up to 0.01; V: 0.05 to 0.25; Nb: 0.005 to 0.20; Al: 0.010 to 0.100; B: up to 0.0005; Ca: 0 to 0.003; O: up to 0.01; N: up to 0.007; the rest is iron and impurities. Steel has a microstructure consisting of tempering martensite and residual austenite in an amount of less than 2 % by volume. Size number of the crystal grains of the previous austenite grains is 9.0 or more, numerical density of carbonitride based inclusions with a particle diameter of 50 mcm or more is 10 inclusions/100 mm² or less, and the yield strength is 965 MPa or higher.

EFFECT: high strength and good resistance to sulfide stress cracking.

6 cl, 6 dwg, 3 tbl