METHOD OF PRODUCING HIGH-STRENGTH SHEET STEEL, CHARACTERIZED BY HIGH PLASTICITY, DEFORMABILITY AND WELDABILITY, AND PRODUCED SHEET STEEL Russian patent published in 2020 - IPC C21D6/00 C21D8/02 C23C2/02 C21D9/46 C22C38/02 

FIELD: metallurgy.

SUBSTANCE: for producing sheet steel with applied coating, having given mechanical properties together with high weldability, especially high weldability when contact spot welding is used, method involves production of cold-rolled sheet steel containing the following, wt %: 0.15 ≤ C ≤ 0.23, 1.4 ≤ Mn ≤ 2.6, 0.6 ≤ Si ≤ 1.3, wherein C + Si/10 ≤ 0.30, 0.4 ≤ Al ≤ 1.0, wherein Al ≥ 6 (C+Mn/10) − 2.5, 0.010 ≤ Nb ≤ 0.035, 0.1 ≤ Mo ≤ 0.5, sheet annealing at temperature in range of 860–900 °C to obtain a structure consisting of at least 90 % of austenite and at least 2 % intercritical ferrite, hardening to temperature in range from Ms −10 °C to Ms −60 °C at speed Vc of more than 30 °C/s, heating to temperature RT in range from 410 °C to 470 °C during 60 to 130 s, coating is applied onto the sheet as a result of immersion into the melt and cooling to room temperature. Microstructure contains from 45 to 68 % of martensite, consisting of 85 to 95 % of martensite, subjected to redistribution of carbon and characterized by level of content of C, making, at most, 0.45 %, and fresh martensite; from 10 % to 15 % of residual austenite; from 2 % to 10 % of intercritical ferrite; from 20 % to 30 % of lower bainite.

EFFECT: invention discloses a method of producing high-strength sheet steel characterized by high plasticity, deformability and weldability, and produced sheet steel.

31 cl, 1 dwg, 11 tbl