Thick spring steel 51CrV4 cold-rolled wide steel strip and manufacturing method thereof

The invention discloses a thick spring steel 51CrV4 cold-rolled wide steel strip and a manufacturing method thereof. The manufacturing method comprises the following steps: 1) slowly cooling a hot-rolled steel strip; pickling; first cold rolling; performing spheroidizing annealing for the first time; performing secondary cold rolling; spheroidizing and annealing for the second time; production of the thick spring steel 51CrV4 cold-rolled wide steel strip with the thickness of 3.00-6.00 mm is achieved, the tensile strength of the produced steel strip is 510-680 MPa, the yield strength is 380-460 MPa, the ductility is 27.0-34.0%, the Rockwell hardness HRB is 80-90, the annealing spheroidizing rate is larger than or equal to 95%, and the technical problems that the thick spring steel 51CrV4 cold-rolled wide steel strip is large in rolling difficulty, complex in production procedure, high in manufacturing cost, poor in thickness precision control and the like are solved. And the size precision and the quality of