Cold-rolled martensite steel plates and the method of manufacturing them.

Abstract

The composition of cold-rolled graphite steel sheets includes the following elements: 0.3% < C < 0.4%; 0.5% < Mn < 1%; 0.2% < Si < 0.6%; 0.1% < Cr < 1%; 0.01% < Al < 1%; 0.01% < Mo < 0.5%; 0.001% < Ti < 0.1%; 0% < S < 0.09%; 0% < ρ < 0.09%; 0% < N < 0.09%; 0% < Nb < 0.01%; 0% < V < 0.1%; 0% < Ni < 1%; 0% < Cu < 1%; 0% < B < 0.05%; 0.001% < Ca < 0.01%; 0% <Sn< 0.1%; 0% < Pb< 0.1%; 0% < Sb< 0.1%; The remaining composition includes iron and unavoidable impurities due to the processing, the microstructure of the steel, expressed as a percentage of area, at least 95% niactensite, the cumulative amount of ferrite and bainite is between 1% and 5%, and the arbitrary amount of remaining austenite is between 0% and 2%. The invention also relates to the method of producing this steel plate.