COLD-ROLLED AND COATED STEEL SHEET AND METHOD FOR ITS PRODUCTION Russian patent published in 2023 - IPC C21D8/02 C21D9/46 C22C38/12 C22C38/14 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention relates specifically to cold-rolled coated steel sheets used in the automotive industry. The sheet has a composition that includes the following elements, expressed in % by weight: 0.140 ≤ carbon ≤ 0.2, 1.5 ≤ manganese ≤ 2.15, 0.5 ≤ silicon ≤ 0.8, 0.4 ≤ aluminium ≤ 0.8, 0 ≤ phosphorus ≤ 0.09, 0 ≤ sulphur ≤ 0.09, 0 ≤ nitrogen ≤ 0.09, 0.01 ≤ niobium ≤ 0.1, 0.01 ≤ titanium ≤ 0.1, optionally one or more of the following: 0 ≤ chromium ≤ 0.1, 0 ≤ nickel ≤ 3.0 ≤ calcium ≤ 0.005, 0 ≤ copper ≤ 2.0 ≤ molybdenum ≤ 0.5, 0 ≤ vanadium ≤ 0.1, 0 ≤ boron ≤ 0.003, 0 ≤ cerium ≤ 0.1, 0 ≤ magnesium ≤ 0.010, 0 ≤ zirconium ≤ 0.010, the rest is iron and inevitable impurities. The microstructure of said steel sheet includes, in area fractions, 40 to 60% of intercritical ferrite, 25 to 45% converted ferrite, 8% to 20% retained austenite, 5% to 20% fresh martensite, 0 to 10% bainite, with the combined amount of intercritical and converted ferrite being between 75% and 85%.

EFFECT: sheet has high strength characteristics and high moldability.

26 cl, 4 tbl