METHOD OF PRODUCTION OF COLD ROLLED METAL OF UPGRADED STRENGTH Russian patent published in 2009 - IPC C21D8/04 C21D9/48 C22C38/06 

FIELD: metallurgy.

SUBSTANCE: method consists in steel melting, in casting slabs, in slabs hot rolling into bands, in water cooling, in winding bands in coils, in cold rolling, in re-crystallisation annealing in bell-type furnace and in pinch rolling; also there is melted steel containing, wt %: carbon - 0.05-0.10, silicon - not more, than 0.30, manganese - 0.25-1.20, aluminium 0.01-0.07, nitrogen - not more, than 0.009, niobium and /or titanium - 0.01-0.08, iron and unavoidable impurities - the rest; hot rolling is performed with the temperature of rolling finish 820-875°C; winding of hot rolled bands is carried out with the temperature 510-640°C; re-crystallisation annealing is performed at the temperature of 600-700°C; duration of re-crystallisation annealing in the bell-type furnace lasts 9-21 hours, pinch rolling is executed with reducing 0.8-2.1%. According to the invention contents of carbon, manganese and temperature of annealing are connected with minimal yield point (grade of strength) by dependencies [C]=[0.0416·1n(G_str)-0.167]±0.015, %, [Mn]=(0.0035·Gstr-0.46)±0.20, %; T_anneal≥(810-0.5·Gstr), °C, where [C], [Mn] is contents of carbon and manganese in steel, %, G_str - is dimensionless parametre numerically equal to required minimal yield point; 0.0416; 0.167; 0.0035; 0.46; - are empirical coefficients,%, 810; 0.5 are empirical coefficients, °C.

EFFECT: upgraded strength properties of steel at maintaining forming ability, producing steel of required grade of strength.

4 cl, 7 tbl, 3 ex