PRODUCTION METHOD OF COLD-ROLLED STEEL FOR DEEP DRAWING Russian patent published in 2013 - IPC C21D8/04 C22C38/06 C21D9/48 

FIELD: metallurgy.

SUBSTANCE: steel which contains the following, wt %, is made of a strip: carbon 0.02-0.06, silicon 0.005-0.030, manganese 0.08-0.20, phosphorus 0.005- 0.018, sulphur 0.005-0.025, acid-soluble aluminium 0.02-0.05, nitrogen 0.002-0.006, chrome of not more than 0.05, nickel of not more than 0.06, copper of not more than 0.07, vanadium of not more than 0.006, iron and inevitable impurities are the rest; steel pouring, rolling on a continuous wide-band mill, strip coiling, cold rolling, recrystallisation annealing in a bell-type furnace at the temperature of not less than 690°C with regulated heating and pinch rolling is performed. Regulated heating for annealing is performed first at the speed of not less than 30°C/hour to temperature T₁ determined from the ratio of T₁≥350+970[Cr+Ni+Cu] °C; then, from temperature T₁ the heating is performed at the speed of not more than 25°C/hour at least during 3 hours, and after that, at the speed of not more than 40°C/hour to the annealing temperature of not more than 720°C; with that, time of metal residence at temperatures of not less than 690°C is determined from the following ratio: τ₆₉₀≥4+950[V].

EFFECT: improving formability.

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