MANUFACTURING METHOD OF HOT-GALVANISED ROLLED STOCK OF INCREASED STRENGTH Russian patent published in 2009 - IPC C21D8/04 C21D9/48 C22C38/06 C23C2/04 

FIELD: metallurgy.

SUBSTANCE: it is implemented steel smelting, pouring, hot rolling, cooling by water, winding of strips into coils, cold rolling, recrystallisation annealing with application of galvanised coating and temper rolling, herewith it is smelted steel, containing, wt %: 0.025-0.10 carbon, 0.41-0.70 manganese, 0.04-0.12 phosphorus, 0.01-0.08 aluminium, not more than 0.009 nitrogen, iron and unavoidable admixtures - the rest, temperature of hot rolling is maintained in the range 840-905°C, winding temperature - 560-690°C, recrystallisation annealing is implemented at 750-880°C, and temper rolling of strips is implemented with cobbing 0.8-2.1%. Content of carbon, phosphorus and annealing temperature are related with required strength grade by correlations: [C]=(0.0005·K_st-0.065)±0.02; [P]=(0.0005·K_st-0.05)±0.02; T_ann.≥ (900-0.5-K_st), where: [C] - content of carbon in steel, wt %, [P] - content of phosphorus in steel, wt %, T_ann. - recrystallization annealing temperature, °C, K_st - nondimensional factor, numerically equal to required minimal yield point; 0.0005; 0.065; 0.05 - empirical coefficients, %; 900; 0.5 - empirical coefficients, °C.

EFFECT: increasing of steel strength properties with keeping of formability, receiving of steel of required strength grade.

4 cl, 6 tbl