SHEET OUT OF HIGH STRENGTH STEEL POSSESSING HIGHER DUCTILITY AND PROCEDURE OF ITS PRODUCTION Russian patent published in 2011 - IPC C22C38/38 C22C38/14 C21D9/48 C21D8/04 

FIELD: metallurgy.

SUBSTANCE: upon hot rolling slab out of steel contains wt %: from 0.05 to 0.20 C, 0.5 or less Si, from 1.5 to 3.0 Mn, 0.06 or less P, 0.01 or less S, from 0.3 to 1.5 Al, 0.02 or less N, from 0.01 to 0.1 Ti, from 0.0005 to 0.0030 B, from 0.51 to 1.5 Cr, if necessary, from 0.01 to 2.0 Mo, from 0.01 to 0.1 Nb, from 0.01 to 0.12 V, one out of Cu and Ni at their summary contents from 0.01 to 4.0, Fe and unavoidable impurities - the rest. Further, the slab is cold rolled. Produced sheet is annealed at temperature from 780 to 900°C during 300 sec or less and is cooled to temperature 500°C or less at average rate of cooling 5°C/sec or more. Microstructure of sheet steel includes from 20 to 70 vol. % of ferrite, 20 vol. % or more of martensite and less, than 10 vol. % of residual austenite.

EFFECT: improved characteristics of phosphatisation and hot galvanising upon annealing while ensuring ultimate tensile strength 950 MPa or more, higher ductility and low changes of mechanical properties at changeable conditions of annealing.

6 cl, 3 tbl, 2 ex