PROCEDE DE FABRICATION DE PIECES D'ACIER A HAUTE RESISTANCE MECANIQUE ET DUCTILITE AMELIOREE, ET PIECES OBTENUES PAR CE PROCEDE

A method for manufacture of a hot-rolled steel sheet which includes: producing a liquid steel to which manganese, silicon, niobium, and chromium are added, the additions being made in a vacuum chamber, then desulfurizing the liquid metal without increasing its nitrogen content, then adding titanium, said additions being made so as to obtain a liquid metal having a chemical composition where the titanium and nitrogen contents satisfy: Ti/N>3.42, and the carbon, manganese, chromium, and silicon contents satisfy: 2.6C+Mn/5.3+Cr/13+Si/15>=1.1%, then casting a semi-finished product, then heating said semi-finished product to a temperature between 1250° C. and 1300° C. for a holding period at this temperature between 20 minutes and 45 minutes, then hot rolling said semi-finished product to a rolling end temperature TFL between 825° C. and 950° C., to obtain a hot-rolled sheet, then coiling said hot-rolled sheet at a temperature between 500° C. and 750° C. to obtain a hot-rolled and coiled sheet, then pickling the oxide layer formed in the previous steps.