HOT-PRESSED STEEL SHEET PART, METHOD OF ITS MANUFACTURE AND STEEL SHEET FOR HOT PRESSING Russian patent published in 2017 - IPC C22C38/58 C22C38/06 B21D22/20 C21D1/18 

FIELD: metallurgy.

SUBSTANCE: steel features the following chemical composition, in wt %: C: 0.10 to 0.34; Si: 0.5 to 2.0; Mn: 1.0 to 3.0; soluble Al: 0.001 to 1.0; P: 0.05 or less; S: 0.01 or less; N: 0.01 or less; Ti: 0 to 0.20; Nb: 0 to 0.20; V: 0 to 0.20; Cr: 0 to 1.0; Mo: 0 to 1.0; Cu: 0 to 1.0; Ni: 0 to 1.0; Ca: 0 to 0.01; Mg: 0 to 0.01; REM: 0 to 0.01; Zr: 0 to 0.01; B: 0 to 0.01; Bi: 0 to 0.01; the rest is Fe and impurities. The portion of the ferrite area in the steel structure of the surface layer zone extended from the surface down to a depth of 15 mcm is 1.20 times greater than the portion of the ferrite area in the inner layer zone, which is an area except for said surface layer. The inner layer zone has the following steel structure, wt % of the area: ferrite from 10 to 70 and martensite from 30 to 90, and the total area of ferrite and martensite is from 90 to 100. In the inner layer zone, the concentration of Mn in the martensite is equal to or 1.20 times greater than the concentration of Mn in the ferrite.

EFFECT: produced parts have tensile strength of 980 MPa or more with high plasticity and bendability.

12 cl, 3 tbl, 1 ex