METHOD OF PRODUCING ULTRA-HIGH-STRENGTH SHEET STEEL SUBJECTED TO ZINC-PLATING WITH ANNEALING, AND OBTAINED SHEET STEEL SUBJECTED TO ZINC-PLATING WITH ANNEALING Russian patent published in 2019 - IPC C21D9/46 C22C38/00 C22C38/06 C22C38/22 C22C38/34 C22C38/38 C23C2/02 C23C2/06 C23C2/28 C23C2/40 

FIELD: metallurgy.

SUBSTANCE: disclosed method involves the following successive steps: obtaining cold-rolled sheet steel made from steel, having chemical composition, wt. %: 0.34 ≤ C ≤ 0.45, 1.50 ≤ Mn ≤ 2.30, 1.50 ≤ Si ≤ 2.40, 0 < Cr ≤ 0.7, 0 ≤ Mo ≤ 0.3, 0.10 ≤ Al ≤ 0.7, optionally 0 ≤ Nb ≤ 0.05 and a residue in form of Fe and unavoidable impurities, annealing of cold-rolled sheet steel at annealing temperature of AT greater than the Ac3 transformation temperature for steel, quenching of annealed sheet steel as a result of its cooling down to quenching temperature QT, which is lower than temperature of Ms conversion for steel, and enclosed within 150 °C to 250 °C, and repeated heating of steel sheet subjected to hardening to distribution temperature of RT in range from 350 °C to 450 °C and storage of sheet steel at temperature of distribution of PT during time distribution Pt, which is at least 80 seconds, and coating steel sheet by zinc coating with annealing at GAT fusion temperature, which is in range from 470 °C to 520 °C. Also disclosed is sheet steel, which is subjected to galvanizing with annealing, and made from said steel, which has steel structure consisting of 50–70 % of martensite, residual austenite and bainite.

EFFECT: invention relates to production of coated steel sheet characterized by ultimate tensile strength TS of at least 450 MPa and total TE elongation of at least 17 %.

24 cl, 2 tbl