The present invention provides a cold-rolled and annealed steel sheet with a strength greater than 1200 MPa, the composition of which includes, the contents being expressed by weight: 0.10%≦C≦0.25%, 1%≦Mn≦3%, A≧0.010%, Si≦2.990%, S≦0.015%, P≦0.1%, N≦0.008%, it being understood that 1%≦Si+Al≦3%, it being understood that Cr+3Mo≧0.3%, Ti in an amount such that Ti/N≧4 and Ti≦0.040%. A balance of the composition includes iron and inevitable impurities resulting from the smelting. The microstructure of the steel includes 15 to 90% bainite, the remainder includes martensite and residual austenite.