COLD-ROLLED AND HEAT-TREATED SHEET STEEL AND METHOD FOR ITS PRODUCTION Russian patent published in 2021 - IPC C22C38/38 C22C38/34 C22C38/28 C22C38/26 C22C38/24 C22C38/18 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy, namely to heat-treated and cold-rolled steel sheet used for the manufacture of structural or safety parts in a vehicle. The sheet is made of steel containing, in wt%: 0.18 ≤ carbon ≤ 0.24, 1.5 ≤ manganese ≤ 2.5, 1.2 ≤ silicon ≤ 2, 0.01 ≤ aluminum ≤ 0.06, 0.2 ≤ chromium ≤ 0.5, phosphorus ≤ 0.02, sulfur ≤ 0.03, if necessary at least one of: niobium ≤ 0.06, titanium ≤ 0.08, vanadium ≤ 0.1 and calcium ≤ 0.005, the rest is iron and inevitable impurities. The sheet has a microstructure including, when expressed in terms of surface fractional concentrations, 0% to 15% of tempered martensite, 10% to 15% of retained austenite, and optionally up to 30% of ferrite, the remainder being bainite. The bainite content is at least 55%. An inner oxide layer having thickness of 3 mcm or less is formed on both surfaces of the steel sheet.

EFFECT: steel sheet has the required strength characteristics and high phosphating capacity.

18 cl, 6 dwg, 4 tbl