METHOD FOR PRODUCTION OF HIGH-STRENGTH ULTRA LOW CARBON COLD-ROLLED STEEL WITH HIGH DUCTILITY Russian patent published in 2022 - IPC C21D8/04 C21D9/48 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to the cold-rolled strip production technology intended for the manufacture of automobile parts by stamping. The method for production of cold-rolled strips of high-strength special ultra low-carbon steel includes steel smelting, casting into slabs, hot rolling, winding, etching, cold rolling, recrystallization annealing and strip skin passing. Steel is smelted, containing, wt. %: carbon 0.001-0.006, silicon no more than 0.3, manganese 0.3-1.6, phosphorus no more than 0.1, aluminum no more than 0.1, titanium no more than 0.12, niobium no more than 0.09, sulfur no more than 0.012, nitrogen no more than 0.012, chromium no more than 0.07, nickel no more than 0.07, copper no more than 0.07, iron and unavoidable impurities the rest. Cold rolling is carried out with a total compression of 65-90%, and recrystallization annealing of the strip is carried out in bell-type furnaces to a temperature of 751 - 830°C. Alternatively, recrystallization annealing of the strip is carried out in bell-type furnaces at a temperature of 730 - 750°C, while the content of titanium and phosphorus is chosen so that the Ti/P ratio is at least 0.92. Otherwise, recrystallization annealing of the strip is carried out in bell-type furnaces at a temperature of 650 - 729°C, while the titanium and phosphorus content is selected so that the Ti/P ratio is in the range of 0.62 - 0.92.

EFFECT: high strength is obtained while maintaining high plasticity.

3 cl, 3 ex