HIGH STRENGTH GALVANISED STEEL PLATE WITH EXCELLENT DEFLECTIVITY AND METHOD OF ITS MANUFACTURING Russian patent published in 2015 - IPC C22C38/06 C22C38/04 C21D8/02 C23C2/06 C23C2/26 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, particularly, to high-strength galvanised steel plate used in motor-car production. Steel contains the following, wt %: C from 0.075 to 0.30, Si from 0.30 to 2.50, Mn from 1.30 to 3.50, P from 0.001 to 0.05, S from 0.0001 to 0.01, Al from 0.005 to 1.50, N from 0.0001 to 0.01, O from 0.0001 to 0.01, and rest is for Fe and inevitable admixtures. In range from 1/8 to 3/8 of thickness of basic steel plate the coefficient of excess K* of hardness distribution between 2% hardness and 98% hardness is -0.30 or below, and plate structure contains residual austenite 8% or below of volume. Ratio between Vickers hardness of the surface layer of the basic steel plate and Vickers hardness at 1/4 of thickness of the basic steel plate is from 0.35 to 0.70, and iron content in the alloyed layer of the galvanic coating is from 8 wt % to 12 wt %.

EFFECT: production of plate with maximum tensile strength 900 MPa or over, and high bending ability.

9 cl, 23 tbl, 1 ex