ROLLED STOCK FOR CASING AND TUBING PIPES AND METHOD OF ITS PRODUCTION

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to metallurgy, namely, to production of roll stock with thickness of 4–20 mm for production of high-strength tubing and casing pipes, mainly of small diameter, which are used in aggressive media containing hydrogen sulphide and carbon dioxide. Rolled stock is made from steel of the following chemical composition, wt%: carbon 0.27–0.40, manganese 1.0–1.5, silicon 0.30–0.80, aluminum 0.02–0.06, chromium not more than 0.08, nickel not more than 0.08, copper not more than 0.08, vanadium not more than 0.01, niobium not more than 0.01, titanium not more than 0.01, molybdenum not more than 0.01, calcium not more than 0.005, nitrogen not more than 0.008, sulfur not more than 0.005, phosphorus not more than 0.012, iron and unavoidable impurities – balance, wherein value of carbon equivalent, calculated by expression C_eq=C+Mn/6, ranges from 0.47 to 0.63. Rolled iron has a ferrite-pearlite microstructure containing ferrite of polyhedral morphology with low density of dislocations and pearlite with equilibrium morphology, perlite fraction is not less than 55 %, time resistance σ_t is not less than 665 MPa, yield point σ_y is from 379 to 552 MPa, relative elongation δ₅ is not less than 19 % and KV impact operation at 20 °C is not less than 27 J.;EFFECT: high complex of mechanical properties.;2 cl, 1 tbl, 1 ex