HOT-ROLLED AND HEAT TREATED STEEL SHEET AND METHOD FOR ITS MANUFACTURE Russian patent published in 2023 - IPC C21D6/00 C21D9/46 C21D8/02 C22C38/02 C22C38/06 C22C38/12 C22C38/32 C22C38/38 B23K11/11 

FIELD: metallurgy.

SUBSTANCE: invention relates to a high-strength steel sheet with suitable weldability. Hot-rolled and heat-treated steel sheet made of steel having a composition containing, wt.%: C 0.03-0.18, Mn 6.0-11.0, Mo 0.05-0.5, B 0.0005-0.005, S ≤ 0.010, P ≤ 0.020, N ≤ 0.008, and optionally containing one or more of the following: Al < 3, Si ≤ 1.20, Ti ≤ 0.050, Nb ≤ 0.050, Cr ≤ 0.5, the rest of the composition is iron and inevitable impurities resulting from smelting. The sheet has a microstructure that includes, in fractions of the surface: 10 - 60% retained austenite, 40 - 90% ferrite, 0 to less than 5% martensite, 0 to less than 0.8% carbides, and an inhomogeneous distribution of manganese with areas below and above the nominal value of manganese. A weld obtained by resistance spot welding of two parts made of hot-rolled and heat-treated steel sheet of the composition mentioned. The weld has α, which is not less than 30 daN/mm², where α is the ratio of the value of the transverse tensile strength to the product of the diameter of the weld point and the thickness of the substrate.

EFFECT: obtaining a steel sheet with high impact strength and weldability.

10 cl, 2 dwg, 4 tbl, 36 ex