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

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely, to heat-treated cold-rolled steel sheet used as material for production of automotive parts. Sheet has the following composition, wt.%: 0.1 ≤ carbon ≤ 0.25, 2.15 ≤ manganese ≤ 2.9, 0.1 ≤ silicon ≤ 0.8, 0.1 ≤ aluminium ≤ 0.9, 0.05 ≤ chrome ≤ 0.5, 0 ≤ phosphorus ≤ 0.09, 0 ≤ sulphur ≤ 0.09, 0 ≤ nitrogen ≤ 0.09, 2.4 ≤ carbon + manganese ≤ 3.0, if necessary, at least one element from: 0 ≤ niobium ≤ 0.1, 0 ≤ titanium ≤ 0.1, 0 ≤ vanadium ≤ 0.1, 0 ≤ molybdenum ≤ 1, 0 ≤ nickel ≤ 1, 0 ≤ calcium ≤ 0.005, 0 ≤ boron ≤ 0.01, 0 ≤ cerium ≤ 0.1, 0 ≤ magnesium ≤ 0.05 and 0 ≤ zirconium ≤ 0.05, the rest is iron and unavoidable impurities. Microstructure of the sheet includes, in area fractions of 20–70% of martensite, 5–6% of intercritical ferrite, 5–30% of converted ferrite, 8-20% of residual austenite, wherein content of carbon in residual austenite is 0.8–1.1 wt.%, and 1–20% of bainite, wherein total amount of intercritical and converted ferrite is 15–65%.

EFFECT: sheet has high mechanical properties.

19 cl, 4 tbl