METHOD OF PRODUCING LOW-ALLOY ROLLED STOCK Russian patent published in 2025 - IPC C21D7/13 C21D8/02 C22C38/58 C22C38/54 C22C38/50 C22C38/48 C22C38/46 C22C38/44 C22C38/42 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to production of rolled coils used for production of spiral seam pipes. Steel is melted with the following chemical composition, wt.%: carbon from more than 0.1 to 0.2, silicon from 0.1 to 0.4, manganese from 1.2 to 1.8, sulphur not more than 0.010, phosphorus not more than 0.015, chromium is not more than 0.04, nickel not more than 0.04, copper not more than 0.04, aluminium 0.02–0.08, molybdenum not more than 0.1, vanadium 0.01–0.1, titanium 0.005–0.05, niobium 0.01–0.1, boron not more than 0.0015, nitrogen not more than 0.01, iron and unavoidable impurities are the rest. Out-of-furnace treatment of steel is carried out, its continuous casting with production of slabs and their austenization at temperature of 1180–1300 °C. Rough rolling is performed to the thickness of the semi-finished product, which is equal to 2–4 times of the finished rolled stock, and finished at temperature of 1050–1130 °C. Finishing rolling is started at temperature from 940 °C to 1030 °C and finished at temperature of 820–910 °C. Rolled stock is cooled first at rate of 6–10 °C/s for 20–70 s, and then at a rate of not more than 7 °C/s to coiling temperature 550–620 °C and winding into a roll is performed.

EFFECT: rolled stock has the required level of mechanical properties, namely yield point, including at angle of 35 and 45 degrees, not less than 415 MPa, tensile strength, including at angle of 35 and 45 degrees, not less than 520 MPa, relative elongation, including at angle of 35 and 45 degrees, not less than 27%, impact work KV at minus 10 degrees of not less than 40 J/cm², ratio of yield strength to tensile strength is not more than 0.83% and hardness HV10 is not more than 250.

2 cl, 3 tbl