Cold-rolled and annealed steel sheet and manufacturing method

A cold-rolled and annealed steel sheet, having a composition comprising, by weight percent:

• 0.060%≤C≤0.085%
• 1.8%≤Mn≤2.0%
• 0.4%≤Cr≤0.6%
• 0.1%≤Si≤0.5%
• 0.010%≤Nb≤0.025%
• 3.42N≤Ti≤0.035%
• 0≤Mo≤0.030%
• 0.020%≤Al≤0.060%
• 0.0012%≤B≤0.0030%
• S≤0.005%
• P≤0.050%
• 0.002%≤N≤0.007%
• a remainder of the composition being iron and unavoidable impurities resulting from smelting, the cold-rolled and annealed steel sheet having a microstructure consisting of, in area fraction:
• at least 34% and at most 80% bainite,
• at least 10% and at most 16% martensite, and
• at least 10% and at most 50% ferrite, wherein an area fraction of unrecrystallized ferrite in the ferrite, with respect to the whole microstructure, is less than 30%;
• the martensite consisting of self-tempered martensite and fresh martensite, an area fraction of self-tempered martensite, with respect to the whole microstructure, being at least 4% and at most 10%, an area fraction of fresh martensite with respect to the whole microstructure, being 0% or more and at most 12%,
• wherein the cold-rolled and annealed steel sheet has a tensile strength TS of at least 780 MPa and at most 900 MPa, a yield strength YS of at least 350 MPa and at most 450 MPa, a total elongation TE of at least 15%, and a hole expansion ratio HER, measured according to ISO standard 16630:2009, of at least 35%.