COLD-ROLLED AND ANNEALED LOW-DENSITY STEEL SHEET, METHOD OF ITS PRODUCTION AND USE OF SUCH STEEL FOR PRODUCTION OF VEHICLE PARTS Russian patent published in 2024 - IPC C21D8/02 C21D9/46 C22C38/02 C22C38/04 C22C38/06 C22C38/08 C22C38/14 C22C38/16 C22C38/38 

FIELD: metallurgy.

SUBSTANCE: invention relates to low-density steel sheet with duplex microstructure, and can be used for production of internal or external panels of vehicles, such as ground vehicles. Cold-rolled and annealed low-density steel sheet contains, wt.%: 0.12 ≤ carbon ≤ 0.25, 3 ≤ manganese ≤ 10, 3.5 ≤ aluminum ≤ 6.5, 0 ≤ phosphorus ≤ 0.1, 0 ≤ sulfur ≤ 0.03, 0 ≤ nitrogen ≤ 0.1, 0 ≤ silicon ≤ 2, 0.01 ≤ niobium ≤ 0.03, 0.01 ≤ titanium ≤ 0.2, 0 ≤ molybdenum ≤ 0.5, 0 ≤ chromium ≤ 0.6, 0.01 ≤ copper ≤ 2.0, 0.01 ≤ nickel ≤3.0, 0 ≤ calcium ≤0.005, 0 ≤ boron ≤ 0.01, 0 ≤ magnesium ≤ 0.005, 0 ≤ zirconium ≤0.005, 0 ≤ cerium ≤ 0.1, rest includes iron, steel sheet has microstructure, including 60–90% of delta-ferrite, 8–30% of residual austenite, having average grain size of 0.6–2 mcm, 1.0–10% of alpha-ferrite with average grain size of 0.6–2 mcm and 0–2% of kappa-emissions (Fe,Mn)₃AlC_x, where x is strictly below 1.

EFFECT: sheet has relative density below 7.3 g/cm³, tensile strength of at least 600 MPa and uniform elongation of at least 17.5%.

15 cl, 4 tbl, 6 ex