MANUFACTURING METHOD FOR WORK-HARDENED STEEL PARTS WITH COATING AND PRE-COATED SHEETS FOR PRODUCING THESE PARTS Russian patent published in 2017 - IPC C22C38/32 C21D1/74 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: invention relates to a cold-rolled and annealed sheet with thickness of 0.5-2.6 mm consisting of a steel substrate for heat treatment and metal pre-coating on at least two major surfaces of the steel substrate. The composition of the steel substrate contains, wt %: 0.07≤C≤0.5, 0.5≤Mn≤3, 0.02≤Si≤0.5, 0.01≤Cr≤1, Ti≤0.2, Al≤0.25, S≤0.05, P≤0.1, 0.0005≤B≤0.010, if required 0.0005≤Ca≤0.005, everything else is iron and unavoidable impurities including oxygen containing O₀. The substrate contains a decarburized area on the surface of each two major surfaces, the deapth of which p50% is 6-30 micrometers, where p50% is the depth at which the carbon content is 50% of the mentioned C content. The sheet does not contain an iron oxide layer between the mentioned substrate and metal pre-coating and, under the interface between the pre-coating and mentioned substrate at the depth of 0-5 micrometers, beginning with the specified interface, has an average content of O_m. Where O_m/O₀ is more than 15.

EFFECT: high strength and bendability of sheets.

22 cl, 16 dwg, 2 ex