COLD ROLLED STEEL PRODUCING METHOD FOR DEEP DRAWING Russian patent published in 2006 - IPC C21D8/04 C22C38/06 

FIELD: ferrous metallurgy, namely cold sheet forming, particularly motor vehicle parts.

SUBSTANCE: method comprises steps of melting steel, casting it, hot rolling in rough and finish stand group of continuous wide rolling mill, coiling strip, cold rolling, subjecting it to recrystallization annealing in hood furnace at temperature no less than 690°C and skin pass rolling of strip. Melt steel contains, mass %: carbon, 0.01 -0.06; silicon, 0.003 - 0.030; manganese, 0.05 - 0.25; phosphorus, 0.003 - 0.020; sulfur, 0.002 - 0.023; acid soluble aluminum, 0.01 - 0.06; nitrogen, 0.002 -0.007; iron and inevitable impurities, the balance while satisfying next relations: [Mn]x{S]≤ 0.045 and 5 ≤ [Al}/[N]≤ 20. Hot rolling in rough stand group is ended when thickness of rolled piece is 35 mm and more at temperature Tp ≥ 1050 + 8000[Mn][S]. Heating at recrystallization annealing is realized at first up to 450 - 500°C for time period no more than 10 h. After temperature 450 - 500°C is achieved heating is realized at rate no more than 20°C/h at least till 550 - 600°C and then at rate no more than 50°C/h till annealing temperature.

EFFECT: improved formability of steel at keeping its surface quality.

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