HIGH-HARDNESS HOT-ROLLED STEEL PRODUCT AND METHOD OF MANUFACTURING SAME Russian patent published in 2018 - IPC C21D8/02 C22C38/08 C22C38/04 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, specifically the production of a hot-rolled steel product, which is a hot-rolled strip or steel plate. Steel slab having the following chemical composition, wt %: C 0.25–0.45, Si 0.01–1.5, Mn more than 0.35 and less than or equal to 3.0, Ni 0.5–4.0, Al 0.01–1.2, Cr less than 2.0, Mo less than 1.0, Cu less than 1.5, V less than 0.5, Nb less than 0.2, Ti less than 0.2, B less than 0.01, Ca less than 0.01, the balance is iron and inevitable impurities, is heated to temperature T_heat in the range of 950–1350 °C. Temperature equalization stage is provided, hot rolling is performed in the temperature range from A_r3 up to 1300 °C to obtain hot-rolled steel material and direct quenching of hot-rolled steel material from rolling heating to a temperature below Ms. Steel product has a martensitic structure, wherein the structure of the initial austenitic grain of the obtained steel product is elongated in the rolling direction and has a ratio of length to width greater than or equal to 1, 2.

EFFECT: high Brinell hardness of at least 450 HBW, improved weldability, high low-temperature toughness and low risk of cracking during hardening.

19 cl, 4 dwg, 3 tbl