STEEL MATERIAL AND STEEL PIPE FOR OIL WELLS Russian patent published in 2019 - IPC C22C38/30 C22C38/52 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to steel material used for production of steel pipes for oil wells. Material contains, wt. %: C: 0.15–0.45; Si: 0.10–1.0; Mn: 0.10 – less than 0.90, P: 0.05 or less, S: 0.01 or less, Al: 0.01–0.1; N: 0.010 or less; Cr: 0.1–2.5; Mo: 0.35–3.0; Co: 0.50–3.0; Cu: 0–0.5; Ni: 0–0.5; Ti: 0–0.03; Nb: 0–0.15; V: 0–0.5; B: 0–0.003; Ca: 0–0.004; Mg: 0–0.004; Zr: 0–0.004; rare-earth metal: 0–0.004, the rest being Fe and impurities. Microstructure contains volume ratio of 90 % or more of tempered martensite, and composition satisfies the following expressions: C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15-Co/6+α≥0.50, (3C+Mo+3Co)/(3Mn+Cr)≥1.0 and an effective B=B-11(N-Ti/3.4)/14, where α is 0.250 with an effective B of 0.0003 % or more and equal to 0 with an effective B of less than 0.0003 %.

EFFECT: material has excellent resistance to SSC even in a medium with high pressure H₂S.

17 cl, 3 dwg, 2 tbl