Ultra high tensile strength steel cord

Commercialization of 0.20 mm/4,000 MPa ultra high tensile strength steel cord has been achieved by the improvement of ductility during wire drawing based on 0.9%C hypereutectoid steel wire rods. Although steel cord is used for belt and carcass parts of trucks and buses, the carcass parts of passenger car tires have been made of polyester. For the first time, 4,000 MPa steel cord has been used for the carcass parts of passenger car tires. In the case of fine steel wire, strengthening by drawing is more effective than strengthening by patenting, and for 4,000 MPa, the strengthening ratio by drawing reaches 65%. Clean hypereutectoid steel wire rods with little center segregation and undeformable inclusions are fundamental, but it is very important to have work hardening and wire uniform deformation at the time of fine drawing. This report describes the strengthening mechanism and improvement of ductility during wire drawing of hypereutectoid steel which has greatly contributed to the commercialization of 4,000 MPa steel cord.