Two-phase steel and method for the fabrication of the same

Abstract

The invention describes a two-phase steel comprising 8-12 wt. % Mn, 0.3-0.6 wt. % C, 1-4 wt. % Al, 0.4-1 wt. % V, and a balance of Fe. The steel has martensite and retained austenite phases, and may include vanadium carbide precipitations. A method for making the two-phase steel involves the steps of (a) hot rolling the ingots of the composition to produce a plurality of thick steel sheets, (b) treating the steel sheets by an air cooling process, (c) warm rolling the steel sheets at a temperature in the range of 300-800° C. with a thicknesses reduction of 30-50%, (d) annealing the steel sheets a first time at a temperature in the range of 620-660° C. for 10-300 min, (e) cold rolling the steel sheets at room temperature with a thickness reduction of 10-30% to generate hard martensite, and (f) annealing the steel sheets a second time at a temperature in the range of 300-700° C. for 3-60 min to facilitate the partitioning of carbon and release the residual stress n martensite.