HEAT-TREATED COLD-ROLLED STEEL SHEET AND METHOD OF ITS MANUFACTURING Russian patent published in 2024 - IPC C21D8/02 C22C38/60 C22C38/38 C22C38/32 C22C38/28 C22C38/26 C22C38/24 C22C38/22 C22C38/20 C22C38/40 C22C38/58 C22C38/54 C22C38/50 C22C38/48 C22C38/46 C22C38/44 C22C38/42 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: invention relates to production of cold-rolled steel sheet used as material for fabrication of structural or safety parts of a vehicle. Cold-rolled sheet has a composition containing the following elements, wt.%: 0.05 ≤ carbon ≤ 0.15, 1.8 ≤ manganese ≤ 2.7, 0.1 ≤ silicon ≤ 1, 0.01 ≤ aluminum ≤ 0.8, 0.1 ≤ chromium ≤ 0.9, 0.002 ≤ phosphorus ≤ 0.09, 0.0001 ≤ titanium ≤ 0.1, 0.0005 ≤ boron ≤ 0.003, 0.01 ≤ niobium ≤ 0.1, sulfur ≤ 0.09, nitrogen ≤ 0.09, optionally, at least one of the following elements: 0 ≤ vanadium ≤ 0.2, 0 ≤ molybdenum ≤ 0.2, 0 ≤ nickel ≤ 2, 0 ≤ copper ≤ 2, 0 ≤ calcium ≤ 0.005, cerium ≤ 0.1, magnesium ≤ 0.05 and zirconium ≤ 0.05, the rest is iron and unavoidable impurities. Microstructure of steel sheet includes, in area fractions, 40–60% of martensite, 15–40% of intercritical ferrite, 10–35% of total amount of converted ferrite and bainite and 0–5% of residual austenite.

EFFECT: sheet has both high strength and high total elongation.

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