Patent ID: 9403200
Filing Date: 2016-08-02
CPC Classification: B21C,C21D,D07B

Claim Text:
1. A process for producing a carbon steel wire having a carbon content of 0.50 to 1.10% by mass, wherein a ratio of a hardness of a surface layer portion on a cross section orthogonal to a longitudinal direction and a hardness of a surface layer portion on a longitudinal section in the longitudinal direction is represented by a coefficient X 1 , and a ratio of a hardness of a center portion on the cross section and a hardness of a center portion on the longitudinal section is represented by a coefficient X 2 , wherein X and wherein the carbon steel wire has a tensile strength of 4000 MPa or higher, wherein, in a final wet wire drawing process, when a carbon steel wire having a carbon content of 0.50 to 1.10% by mass and having a pearlite structure is subjected to a wire drawing process in each die, the number of dies in which a coefficient A represented by the following formula composed of the die reaction and the diameter at the die exit:  is 90 or lower is all the dies, and wherein a processing strain ε larger than 2.5 is applied in the final wet wire drawing process.