STEEL MATERIAL AND STEEL PIPE FOR OIL WELL Russian patent published in 2019 - IPC C22C38/52 C21D8/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to steel material used for production of steel pipes of oil wells. Material has a chemical composition consisting of, wt%: C: from 0.15 to 0.45; Si: from 0.10 to 1.0; Mn: from 0.10 to 0.8; P: 0.050 or less; S: 0.010 or less; Al: from 0.01 to 0.1; N: 0.010 or less; Cr: from 0.1 to 2.5; Mo: from 0.35 to 3.0; Co: from 0.05 to 2.0; Ti: from 0.003 to 0.040; Nb: from 0.003 to 0.050; Cu: from 0.01 to 0.50; Ni: from 0.01 to 0.50; V: from 0 to 0.5; B: from 0 to 0.003; W: from 0 to 1.0; Ca: from 0 to 0.004; Mg: from 0 to 0.004; rare-earth metal: 0 to 0.004, the rest is iron and impurities. Composition of material satisfies the following conditions: C+Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15 - Co/6+α≥0.70, (3C+Mo+3Co)/(3Mn+Cr)≥1.0 and Effective B = B-11(N-Ti/3.4)/14, where α is equal to 0.250 when the effective B amount is 0.0003 wt% or more, or is equal to zero when the effective B amount is less than 0.0003 wt%. Microstructure contains total of 90 vol% or more of tempered martensite and tempered bainite, the diameter of the preceding austenite grain in the microstructure is less than 5 mcm, and the martensite and bainite block diameter in the microstructure is less than 2 mcm.

EFFECT: manufactured pipes have high resistance to sulphide cracking under stress even in medium H₂S with high pressure.

9 cl, 2 dwg, 7 tbl