HOT-ROLLED, COLD-ROLLED AND CLADDED STEEL PLATE HAVING IMPROVED UNIFORM AND LOCAL DUCTILITY AT HIGH DEFORMATION RATE Russian patent published in 2015 - IPC C21D8/02 C22C38/00 C21D9/46 C23C2/06 

FIELD: metallurgy.

SUBSTANCE: invention relates to a hot-rolled, cold-rolled and cladded steel plate, which has improved uniform ductility and local ductility at high deformation rate. According to one version of implementation of the invention, a hot-rolled steel plate has a metallographic structure including the main phase from ferrite with an average grain diameter of not more than 3.0 mcm and the second phase including at least one from martensite, bainite and austenite. In the surface layer, the average grain diameter of the second phase comprises not more than 2.0 mcm, difference (ΔnH_av) between average nano-hardness (nH_αav) of the main phase and average nano-hardness (nH_{2nd av}) of the second phase comprises 6.0-10.0 GPa, difference (ΔσnH) of mean-square deviation of nano-hardness of the second phase and mean-square deviation of ferrite nano-hardness comprises not more than 1.5 GPa, and in the central part, difference (ΔnH_av) between average nano-hardness values comprises at least 3.5 GPa to not more than 6.0 GPa, and difference (ΔσnH) between mean-square deviations of nano-hardness values comprises at least 1.5 GPa.

EFFECT: obtaining a steel plate with relative elongation of at least 23%, local relative elongation of at least 10% at preservation of ultimate tensile strength equal to at least 900 MPa.

6 cl, 8 tbl