HIGH-STRENGTH STEEL WITH GOOD PLASTICITY AND METHOD OF PRODUCING THROUGH PROCESSING BY FINISHING METHOD WITH ZINC BATH DISTRIBUTION Russian patent published in 2017 - IPC C22C38/02 C22C38/06 C21D8/02 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: sheets are made of steel having the specified composition containing the following elements, wt %: 0.15-0.5 carbon, 1-4 manganese; 2 or less of silicon, aluminium or a combination thereof; 0.5 or less molybdenum; 0.05 or less niobium; the rest - iron and other random impurities. The steel sheet is heated to the first temperature (T1), which is, at least, above the temperature, at which the steel sheet undergoes conversion to austenite and ferrite. The steel sheet is cooled to the second temperature (T2) by cooling with a critical cooling rate or higher, with T2 below the temperature (M_s) of the onset of martensitic transformation, and this critical cooling rate is high enough to convert austenite to martensite. And, the said critical cooling rate is defined as the cooling rate, at which the hardness of the steel sheet at room temperature is lower than the maximum hardness of the steel sheet at room temperature by not more than 2 divisions according to the Rockwell HRA scale. The steel sheet is reheated to a distribution temperature that is sufficient to allow carbon diffusion in the structure of the said steel sheet. The austenite is stabilised by holding the steel sheet at a distribution temperature for a holding time sufficient to allow carbon diffusion from martensite to austenite. During the said stage of austenite stabilisation, the steel sheet is hot-dip galvanized or zinc-plated. The steel sheet is cooled to room temperature.

EFFECT: high strength and good formability.

5 cl, 12 dwg, 7 tbl, 9 ex