COLD-ROLLED AND ANNEALED STEEL SHEET AND METHOD OF ITS MANUFACTURE Russian patent published in 2023 - IPC C21D8/02 C21D6/00 C21D9/46 C22C38/02 C22C38/04 C22C38/06 C22C38/12 C22C38/14 C22C38/18 C22C38/22 C22C38/24 C22C38/26 C22C38/28 C22C38/32 C22C38/38 B23K11/11 

FIELD: metallurgy.

SUBSTANCE: high-strength cold-rolled and annealed steel sheet used as a material for the manufacture of structural elements and vehicle body panels. The sheet is made of steel having a composition comprised of the following (wt.%): C: ≤0.03-0.18, Mn: ≤6.0-11.0, Al: ≤0.2-3, Mo: {B>(0,05-0,5) B<B} 0.0005-0.005, S≤ 0.010,P≤ 0.020, N≤ 0.008, optionally at least one element selected from: Si≤ 1.20, Ti≤ 0.050, Nb≤ 0.050, Cr≤ 0.5 and V≤ 0.2, the rest is iron and inevitable impurities formed during smelting. The sheet has a microstructure containing, in surface fractions, from 25 to 54% of retained austenite, from 46 to 75% of ferrite and from 0 to 8% of fresh martensite. The amounts of carbon [C]_A and manganese [Mn]_A in austenite, expressed as percentages by mass, satisfy the condition [C]_A*√[Mn]_A, ranging from 0.48 to 1.8. Heterogeneous re-release of manganese with areas above and below the nominal value of manganese content in the steel sheet is characterized by a deviation of the manganese concentration profile curve of -50 or more.

EFFECT: sheet has the required combination of mechanical properties.

12 cl, 2 dwg, 7 tbl