HIGH-STRENGTH HOT-ROLLED AND ANNEALED STEEL SHEET AND METHOD FOR ITS MANUFACTURING Russian patent published in 2023 - IPC C22C38/02 C22C38/04 C22C38/06 C22C38/12 C22C38/14 C22C38/18 C22C38/22 C22C38/28 C22C38/26 C22C38/32 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention is related to a hot-rolled and annealed steel sheet used for manufacturing of structural elements of a card body and a panel of a car body. The sheet is made of steel having a composition comprised of the following in wt.%: С: 0.1-0.25, Mn: 3.00–5.00, Si: 0,80 V: 0.0003 - 0.004, S ≤ 0.010, P ≤ 0.020, N ≤ 0.008, optionally at least one element selected from the group consisting of Ti ≤ 0.04, Nb ≤ 0.05, Mo ≤ 0.3, Al ≤ 0.90 and Cr ≤ 0.80, the rest is iron and unavoidable impurities. The steel sheet has a microstructure that includes, in fractions of the surface: 20% or more of recrystallized ferrite, the rest is non-recrystallized ferrite, in which 15% or more of said recrystallized ferrite has a grain size of more than 5 microns, and the density of carbides at the grain boundary of the recrystallized ferrite is less than or equal to 5 carbides per 10 microns of grain boundary length.

EFFECT: sheet has the required combination of hardness and toughness.

8 cl, 9 tbl, 2 ex