STEEL SHEET WITH HIGH MECHANICAL STRENGTH, DUCTILITY AND FORMABILITY PROPERTIES, PRODUCTION METHOD AND USE OF SUCH SHEETS Russian patent published in 2017 - IPC C21D8/02 C21D9/46 C22C38/14 C21D1/20 

FIELD: metallurgy.

SUBSTANCE: invention relates to production of cold-rolled steel sheet with strength of more than 1,000 MPa, uniform elongation greater than 12 % and a V-bendability greater than 90°, which contains, wt%: 0.15 ≤ C ≤ 0.25, 1.8 ≤ Mn ≤ 3.0, 1.2 ≤ Si ≤ 2, 0 ≤ A1 ≤ 0.10, 0% ≤ Cr ≤ 0.50 %, 0 ≤ Cu ≤ 1, 0 ≤ Ni ≤ 1, 0 ≤ S ≤ 0.005, 0 ≤ P ≤ 0.020, Nb ≤ 0.015, Ti ≤ 0.020, V ≤ 0.015, Co ≤ 1, N ≤ 0.008, B ≤ 0.001, wherein Mn + Ni + Cu ≤ 3, balance is iron and unavoidable impurities formed during manufacture.

EFFECT: microstructure consists in portions of area of 5–20 % polygonal ferrite, 10–15 % of residual austenite, 5–15 % of martensite, balance is bainite is in form of laths and includes carbides between laths, so that number N of inter-lath carbides larger than 0,1 micrometers per unit of surface area, is less than or equal to 50,000/mm².

15 cl, 3 dwg, 5 tbl