METHOD FOR PRODUCING HIGH-STRENGTH STEEL SHEET AND PRODUCED SHEET Russian patent published in 2019 - IPC C21D8/02 C21D9/46 C22C38/38 

FIELD: metallurgy.

SUBSTANCE: steel sheet obtained by rolling steel containing, wt. %: 0.19–0.22 C, 2–2.6 Mn, 1.45–1.55 Si, 0.15–0.4 Cr, less than 0.020 P, less than 0.05 S, less than 0.08 N, 0.015–0.070 Al, the rest is Fe and inevitable impurities, maintained at an annealing temperature between 860–890 °C for 100–210 s, cooled to a hardening temperature of 220–330 °C, from a temperature of at least 500 °C at a cooling rate of at least 15 °C/s, heated for 115–240 s to the first temperature of overcooking above 380 °C, then within 300–610 seconds to the second overcooking temperature 420–450 °C, cooled to a temperature below 100 °C at a cooling rate of less than 5 °C/s. Steel structure contains more than 80 % of tempered martensite, more than 5 % residual austenite, less than 5 % ferrite, less than 5 % bainite, and less than 6 % fresh martensite.

EFFECT: invention relates to the production of high-strength steel sheet having a tensile strength of YS of more than 1000 MPa, a tensile strength of TS of more than 1150 MPa and an overall elongation of E of more than 8 %.

9 cl, 4 tbl