COLD-ROLLED AND ANNEALED SHEET STEEL, METHOD OF ITS PRODUCTION AND USE OF SUCH STEEL FOR PRODUCTION OF PARTS OF VEHICLES Russian patent published in 2019 - IPC C22C38/04 C22C38/06 C22C38/38 C22C38/58 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to cold-rolled and annealed sheet steel used for production of safety parts or structural parts of vehicles. Said steel contains, wt%: 0.6<C<1.3 %, 15.0≤Mn<35 %, 6.0≤Al<15 %, Si≤2.40 %, S≤0.015 %, P≤0.1 %, N≤0.1 %, optionally, at least one of Ni, Cr and Cu up to 3 % each and, optionally, at least one of B, Ta, Zr, Nb, V, Ti, Mo and W in sum up to 2.0 %, iron and unavoidable impurities making the rest. Microstructure of steel contains at least 0.1 % of intragranular kappa-carbides, optionally up to 10 % of granular ferrite, wherein residue is formed from austenite. At least 80 % of kappa-carbides are characterized by average size of less than 30 nm. Average size of grains and average ratio of sides of austenite grains, respectively, are less than 6 mcm, and from 1.5 to 6, and average grain size and average ratio of sides of ferrite grains in case of its presence, respectively, are less than 5 mcm and less than 3.0.

EFFECT: achieving required properties, in particular tensile strength of not less than 1,000 MPa and yield point of not less than 900 MPa at density less than 7,2.

12 cl, 1 dwg, 4 tbl