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 making safety parts or structural parts of vehicles. Said steel contains, wt%: 0.6<C<1.3, 15≤Mn<35, 6.0≤Al<15, Si≤2.40, S≤0.015, P≤0.1, N≤0.1, optionally one or more elements selected from Ni, Cr and Cu in an individual amount of up to 3 %, and optionally one or more elements selected from B, Ta, Zr, Nb, V, Ti, Mo and W in total amount of up to 2.0 %, the rest being iron and unavoidable impurities. Microstructure of sheet steel comprises at least 0.1 % of intragranular kappa-carbides and optionally up to 10 % of granular ferrite, the rest is austenite, wherein at least 80 % of said kappa-carbides are characterized by an average size of less than 30 nm. Average size of grains and average ratio of sides of austenite grains is less than 6 mcm and 2 to 10 respectively. Average grain size and average ratio of sides of ferrite grains in case of its presence are less than 5 mcm and less than 3.0, respectively.

EFFECT: obtaining sheet steel with density of not more than 7,2 and tensile elongation of at least 5 %.

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