Cold-rolling strip steel with strength and hardness thereof varying in thickness direction and manufacturing method therefor

Abstract

Disclosed is a cold-rolled strip steel with varying strength/hardness in a thickness direction, comprising chemical elements in the following mass percentages: C 0.06-0.3 wt %, Si 0.01-2.5 wt %, Mn 0.5-3 wt %, Al 0.02-0.08 wt % and a balance of Fe and other unavoidable impurities, wherein the cold-rolled strip steel with varying strength/hardness in a thickness direction has a yield strength of ≥420 MPa, a tensile strength of ≥800 MPa, an elongation of ≥11%, and a hardness difference between two surfaces of at least 30 HV, and a method for manufacturing a cold-rolling strip steel with varying strength and hardness thereof in a thickness direction, which is characterized in that, when quenching is performed in the continuous annealing step, an asymmetric quenching and cooling process is performed on both surfaces of the strip steel.

Dependencies are inferred from the claim text.