HIGH-STRENGTH STEEL SHEET GALVANISED BY HOT IMMERSION Russian patent published in 2015 - IPC C23C2/00 C21D9/46 C22C38/00 

FIELD: metallurgy.

SUBSTANCE: steel sheet galvanised by hot immersion contains, wt %: C 0.10-0.4, Si 0.01-0.5, Mn 1.0-3.0, O 0.006 or less, P 0.04 or less, S 0.01 or less, Al 0.1-3.0, N 0.01 or less, Fe and the inevitable polluting impurity - the rest. The steel sheet structure includes, vol %: bainite and martensite 40 or more, residual austenite 8-60, ferrite less than 40, inevitable structure the rest. The steel sheet has a layer from the intermetallic compound consisting of Fe, Al, Zn and the inevitable polluting impurity at the interface between the layer formed by hot galvanisation by immersion and the base steel sheet. Average thickness of the intermetallic compound amounts within 0.1 - 2 microns or less. The size of crystal grain of intermetallic compound amounts 0.01 or more up to 1 micron or less. The arithmetic average of the value Ra of roughness of the surface of the base steel sheet after removal of the layer formed by hot galvanisation by immersion amounts from 0.1 or more up to 2.0 microns or less, and the average length RSm of the level line element in the roughness curve amounts from 5 or more up to 300 microns or less.

EFFECT: exception of cracking and destruction of steel sheet when processing.

4 cl, 3 tbl