HIGH-STRENGTH STEEL PRODUCTS AND THEIR MANUFACTURING METHODS Russian patent published in 2021 - IPC C21D1/18 C21D1/26 C21D6/00 C22C38/06 C23C2/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to products made of high-strength steel with favorable properties, and to methods for annealing such products. The method of heat treatment of a cold-rolled sheet of high-strength steel containing, wt %: from 0.12 to 0.5 C, from 1 to 3 Mn, from 0.8 to 3 combinations of Si and Al, includes a two-stage annealing of the sheet. The first stage of annealing includes stages, at the first of which the sheet is heated to a temperature from 820 to 980°C and held for 20-500 sec., and at the second stage - quenching at a temperature below the end temperature of the martensitic transformation (M_F), followed by cooling below 300°C at a rate that ensures the formation of the martensitic structure. The second stage of annealing includes stages, at the first of which heating and thermal soaking are carried out at a temperature of 720 to 850°C for 15-300 seconds, followed by cooling to the second stage, at which an exposure is carried out at a temperature of 360 to 440°C for no more than 800 seconds. The structure formed during the two-stage annealing in the sheet contains ferrite grains and equiaxed residual austenite grains with an average aspect ratio of residual austenite grains of less than 3:1, and the tensile strength and total relative elongation of the USTTE sheet exceeding 25,000 MPa%.

EFFECT: sheets have high mechanical properties and are characterized by high formability.

31 cl, 16 dwg, 3 tbl, 12 ex