THERMALLY TREATED COLD-ROLLED STEEL SHEET AND METHOD OF ITS MANUFACTURING Russian patent published in 2024 - IPC C21D8/02 C22C38/60 C22C38/02 C22C38/04 C22C38/06 C22C38/18 C22C38/22 C22C38/24 C22C38/26 C22C38/28 C22C38/32 C22C38/38 

FIELD: metallurgy.

SUBSTANCE: invention relates to production of thermally treated and cold-rolled steel sheet, used as material for production of structural parts or parts of vehicle safety. Sheet has a composition containing the following elements in wt.%: 0.09≤carbon≤0.15, 1.8≤manganese≤2.5, 0.2≤silicon≤0.7, 0.01≤aluminium≤0.1, 0≤phosphorus≤0.09, 0≤sulfur≤0.09, 0≤nitrogen≤0.09, optionally, at least one element selected from: 0≤niobium≤0.1, 0≤titanium≤0.1, 0≤chrome≤1, 0≤molybdenum≤1, 0≤vanadium≤0.1, 0≤calcium≤0.005, 0≤boron≤0.01, 0≤cerium≤0.1, 0≤magnesium≤0.05 and 0≤zirconium≤0.05, the rest is iron and unavoidable impurities. Sheet microstructure includes 65–85% of tempered martensite, 0–5% of residual austenite and total content of ferrite and bainite 15–35%. Sheet has tensile strength of 950 MPa or more, total elongation of 8% or more, and hole expansion ratio at least 55%.

EFFECT: steel sheet has the required level of mechanical properties.

18 cl, 4 tbl