MANUFACTURING METHOD OF COLD-ROLLED STRIP (VERSIONS) Russian patent published in 2011 - IPC C21D8/04 C21D9/48 C22C38/20 

FIELD: metallurgy.

SUBSTANCE: there performed is steel making, pouring, hot rolling, water cooling, strip rolling, etching, cold rolling, recrystallisation annealing in bell furnaces and pinch rolling; at that, steel containing the following components is molten, wt %: carbon 0.001-0.006, silicium of not more than 0.30, manganese 0.26-1.60, phosphorus of not more than 0.12, chrome of not more than 0.15, nickel of not more than 0.15, copper of not more than 0.50, vanadium of not more than 0.010, molybdenum of not more than 0.015, aluminium 0.01-0.09, nitrogen of not more than 0.007, sulphur of not more than 0.018, iron and inevitable impurities are the rest; as per the first version, steel includes titanium 0.01-0.09 and niobium of not more than 0.010 at compliance with ratios Ti≥4C+3.43N+1.5S; as per the second version the steel includes titanium 0.01-0.07 and niobium 0.01-0.07 at compliance with ratios Ti≥3.43N, Nb≥7.75C. Hot rolling is completed at 810-910°C; strip coiling is performed at 510-710°C, cold rolling - with total reduction of 40-95%; recrystallisation annealing is performed at 600-750°C with exposure of 8-35 hours, and pinch rolling of strips is performed with reduction of 0.4-2.5% In addition, steel contains boron 0.0005-0.005 wt % and/or calcium 0.0003-0.001 wt %. Carbon equivalent of steel is determined by the ratio C_equiv=C+(Mn+Si)/6≤0.28.

EFFECT: improving strength characteristics of the strip and maintaining high ductility, and provision of deep forming.

6 cl, 5 tbl