MANUFACTURING METHOD OF LOW-ALLOY PLATE STRIPS Russian patent published in 2012 - IPC C21D8/02 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: for obtaining mechanical properties of strips 20-40 mm thick, which correspond to the requirements of strength category K60(X70)-K70(X90), at increase in cold resistance and corrosion resistance of the finished rolled metal, there obtained is steel workpiece containing the following, wt %: 0.04-0.07 C; 0.15-0.35 Si; 0.2-0.3 Cr; 0.2-0.3 Ni; 0.055-0.08 Nb; 0.2-0.3 Mo; Cu≤0.15; 0.02-0.04 V; manganese content is specified depending on carbon content on the basis of the ratio: Mn=(1.5+(0.00033/C²))±0.05, Fe and impurities - the rest; at that, carbon equivalent is C_equiv =0.41-0.46. Roughing-down of the workpiece is performed at temperature of not less than 950°C. Finishing rolling temperature T_"нп" is specified depending on actual thickness of semi-finished rolled stock at cooling-down on the basis of the following ratio: T_"нп" ⁼(K₁*H² _n+K₂*H_п+K₃)=10^oC, where K₁ - empirical coefficient, K₁=-0.15°C/mm²; H_"п" - thickness of semi-finished rolled stock at cooling down, mm; K₂ - empirical coefficient, K₂=45.61°C/mm; K₃ -empirical coefficient, K₃=-2684.1°C. Structure of the finished strips includes ferritic and bainitic components.

EFFECT: improving mechanical properties of strips.

2 cl, 1 ex