FIELD: metallurgy.
SUBSTANCE: steel plate contains base steel plate and formed on its surface by dip galvanising the coating layer with assurance of plate thickness from 0.6 to 5.0 mm. The base plate contains in wt %: C 0.075-0.40, Si 0.01-2.00, Mn 0.80-3.50, P 0.0001-0.100, S 0.0001-0.0100, Al 0.001-2.00, N 0.0001-0.0100, O 0.0001-0.0100, Fe and inevitable admixtures - rest. In range from 1/8 to 3/8 of thickness from surface of the base steel plate with centre 1/4 of plate thickness the structure of the base steel plate contains 3 vol % or more residual austenite phase, 50 vol % or below ferrite phase, and 40 vol % or more solid phase, made by beinite ferrite and/or beinite, tempering martensite and fresh martensite. Average density of dislocations is 5×1013/m2 or over. C content in solid solution of residual austenite phase is from 0.70 to 1.00 wt %. Ratio of intensity of X-ray radiation of iron with face-centred cube lattice during exposure in arbitrary direction of the texture of the residual austenite phase is 3.0 or below. Ratio between grain diameter of residual austenite phase in roll direction and grain size of residual austenite phase in plate width direction is from 0.75 to 1.33.
EFFECT: production of steel plate with high degree of heat strengthening.
11 cl, 18 tbl
