HIGH-STRENGTH HOT-ROLLED STEEL SHEET AND METHOD FOR ITS MANUFACTURING Russian patent published in 2023 - IPC C21D8/02 C22C38/02 C22C38/04 C22C38/06 C22C38/12 C22C38/14 C22C38/38 C22C38/32 C22C38/34 C22C38/28 C22C38/26 C22C38/22 B23K11/11 

FIELD: metallurgy.

SUBSTANCE: invention is related to hot-rolled steel sheet used in the automotive industry. The sheet is made of steel having the following composition, in wt.%: С: 0.10-0.25, Мn: 3.5-5.0, Si: 0.80-1.60 V: 0.0003-0.004, S ≤ 0.010, P ≤ 0.020, N ≤ 0.008, if necessary, at least one of the following elements: Ti ≤ 0.04, Nb ≤ 0.05, Mo ≤ 0.3, Al ≤ 0.90 и Cr ≤ 0.80, the rest is iron and inevitable impurities resulting from smelting. The steel sheet has a microstructure that includes, in fractions of the surface: 50-80% lath bainite with a size ratio greater than or equal to 3, less than 30% granular bainite with a size ratio less than 3, the rest are martensite and martensite-austenite M-A pockets having a size ratio less than or equal to 2, and austenite films, moreover, the total amount of martensite, M-A pockets and austenitic films is 15-35%. Less than 20% of said martensite and said M-A packets have a maximum grain length L_max times maximum grain width W_max greater than 1 mcm².

EFFECT: steel sheet has high mechanical properties, the required level of machinability and weldability.

8 cl, 5 tbl, 1 ex