HIGH STRENGTH AND HIGH DEFORMABLE SHEET STEEL AND METHOD OF ITS PRODUCTION Russian patent published in 2021 - IPC C22C38/12 C21D8/02 B23K11/10 

FIELD: metallurgy.

SUBSTANCE: invention relates to the field of metallurgy and namely to cold-rolled and heat-treated sheet steel used in the automotive industry. The steel has the following chemical composition, wt%: 0,10≤С≤0,25, 3,5≤Mn≤6,0, 0,5≤Si≤2,0, 0,3≤Al≤1,2, 0,10≤Mo≤0,50, S≤0,010, P≤0,020, N≤0,008, if necessary one or more elements selected from: 0,01≤Cr≤1,0, 0,010≤Ti≤0,080, 0,010≤Nb≤0,080, 0,010≤V≤0,30 and 0,0005≤B≤0,004, the rest is iron and inevitable impurities. The steel has a microstructure consisting, in terms of surface fractional concentrations, of: 10% to 45% of ferrite having an average grain size of at most 1.3 mcm, 8% to 30% of retained austenite at most 8% of fresh martensite and at most 2.5% of cementite and redistributed martensite. The product of the surface fractional ferrite concentration by the average ferrite grain size is at most 35 mcm%, and the retained austenite has an Mn content of more than 1.1×Mn%, where Mn% denotes the Mn content of the steel sheet.

EFFECT: steel has the required level of mechanical properties and high deformability.

29 cl, 6 tbl