HOT-GALVANISED COLD-ROLLED STEEL SHEET AND METHOD OF ITS PRODUCTION Russian patent published in 2015 - IPC C22C38/04 C22C38/06 C22C38/38 C21D8/02 C23C2/02 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: plate is made from steel containing the following in wt %: C over 0.10 and below 0.25, Si over 0.50 and below 2.0, Mn over 1.50% and maximum 3.0, P below 0.050, S: 0.010 or less, soluble Al 0.50 or less; N: 0.010 or less, optionally one or more elements selected from Ti, Nb, V, Cr, Mo, B, Ca, Mg, REM and Bi. The sheet structure contains basic phase containing martensite and/or beinite, and/ort beinite ferrite, and secondary phase containing residual austenite. Volume part of the residual austenite is from over 4.0 to below 25.0% of the entire structure, average size of grains is below 0.80 microns, and number density of grains of the residual austenite with size 1.2 mcm or over is 3.0×10^-2 grains/mcm² or below.

EFFECT: sheet has tensile strength 750 MPa or over, has high plasticity, suitability for strain hardening and flanging-drawing.

7 cl, 3 tbl, 1 ex