FIELD: metallurgy.
SUBSTANCE: invention relates to metallurgy, namely to steel material for steel pipes of oil wells for use in acid medium. Material has a chemical composition consisting of, wt %: C: more than 0.45–0.65, Si: 0.10–1.0, Mn: 0.1–1.0, P: 0.050 or less, S: 0.010 or less, Al: 0.01–0.1, N: 0.01 or less, Cr: 0.1–2.5, Mo: 0.25–5.0, Co: 0.05–5.0, Cu: 0–0.50, Ni: 0–0.50, Ti: 0–0.030, Nb: 0–0.15, V: 0–0.5, B: 0–0.003, Ca: 0–0.004, Mg: 0–0.004, Zr: 0–0.004, and rare-earth metal: 0–0.004, Fe and impurities – the rest. Microstructure of material 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 ≥ 0.70, (3C + Mo + 3Co)/(3Mn + Cr) ≥ 1.0 and an effective B = B–11 (N–Ti/3.4)/14, where α in expression is 0.250 with an effective B value of 0.0003 % or more and is equal to 0 with an effective B value of less than 0.0003 %.
EFFECT: providing high strength and excellent resistance to stress corrosion cracking.
17 cl, 2 dwg, 2 tbl
