MANUFACTURING METHOD OF HOT-GALVANISED ROLLED METAL OF HEAVY DUTY Russian patent published in 2009 - IPC C21D8/04 C21D9/48 C22C38/06 C23C2/04 

FIELD: metallurgy.

SUBSTANCE: in manufacturing method of hot-galvanised rolled metal of heavy-duty made of low-alloyed steel for cold-pressing, including steel melting, pouring, hot rolling, cooling by water, winding of strips into coil, cold rolling, recrystallisation annealing with application of galvanised coating and temper rolling, according to invention it is smelted steel, containing, wt %: carbon - 0.05-0.10, manganese - 0.25-0.90, aluminium - 0.01-0.07, nitrogen - not more 0.009, niobium and/or titanium - 0.01-0.08 of each, iron and unavoidable admixtures - the rest. Finishing temperature of hot rolling is maintained in the range 840-905°C, and winding temperature of got-rolled strips - in the range 560-690°C, recrystallisation annealing is implemented at temperature 710-850°C, temper rolling of strips is implemented with draught 0.8-2.1%. C, manganese and annealing temperature are relates to required minimal yield strength (strength grade) by correlations: [C]=[0.0416•ln(K_st)-0.167] ±0.015; [Mn]=(0.0016·K_st+0.034)±0.20; T_ann ≥ (900-0.455·K_st), where [C] - carbon content in steel, %; [Mn] - manganese content in steel, %; T_ann - recrystallisation annealing temperature, °C; K_st - nondimensional factor, numerically equal to required minimal yield strength; 0.0416; 0.167; 0.0016; 0.034 are empirical coefficients, %; 900; 0.455 - empirical coefficients, °C.

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

4 cl, 6 tbl, 1 ex