METHOD OF PRODUCTION OF HOT-ROLLED SHEETS FROM HIGH-STRENGTH STEEL

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to the field of metallurgy, namely to the production of thick steel sheets, used for structural elements operated in arctic conditions, for example, for the production of icebreakers and large-tonnage vessels. Method comprises producing a continuously cast billet of steel containing, mass%: carbon 0.07–0.12, silicon 0.15–0.40, manganese 0.3–0.9, the total content of chromium, nickel and copper is 3.4–4.2, the total content of vanadium, niobium and titanium 0.02–0.07, molybdenum 0.15–0.20, nitrogen is not more than 0.007, aluminum 0.01–0.05, sulfur not more than 0,003, phosphorus is not more than 0.010, iron and impurities remaining, at the same time, the resistance parameter of crack formation during P_st welding does not exceed 0.28 %, austenization of the billet at a temperature of 1,200–1,230 °C, rough rolling to a thickness of 2×t±5 mm, where t is the nominal thickness of the sheet, caving of the rolls, finishing rolling with its completion at a temperature not lower than A_r3+100 °C and thermal improvement of the metal by quenching followed by tempering at a temperature of not more than 680 °C.;EFFECT: obtaining a sheet thickness of 70 mm with a yield strength of at least 500 MPa, a high impact level at a test temperature of 60 °C below zero, including after mechanical aging, level of properties in the part of the temperature of the viscous-brittle transition T_kb and the zero ductility temperature of NDT, as well as increased resistance to layered fractures under tensile stresses in the direction of thickness.;1 cl, 3 tbl