MANUFACTURE OF HIGH STRENGTH HIGH DUCTILITY STEEL WIRE ROD AND HIGH STRENGTH HIGH DUCTILITY EXTRA THIN STEEL WIRE

摘要

PURPOSE:To manufacture the high strength high ductility extra thin wire having excellent stranding workability by subjecting a steel wire rod contg. specified chemical components and having suppressed segregation to specified final patenting and drawing. CONSTITUTION:A steel wire rod constituted of, by weight 0.90 to 1.10% C, =0.4% Si, =0.5% Mn, 0.10 to 0.30% Cr and the balance iron with inevitable impurities and in which the content of Al in the inevitable impurities is regulated to =0.003% is prepd. In the steel wire rod, the maximum value of the segregation zone of C, Mn exceeding Cr1.3 times as much as that of the average compsn. in the wire rod existing within a 1/2 radius from the center of its section is furthermore regulated to =0.01 to the diameter of the wire rod. Next, in the use of the above steel wire rod, its strength after final patenting is regulated to 140 to 160kgf/mm2, its structure is formed so that pro-eutectoid ferrite and pro-eutectoid cementite are present at =0.02% areal ratio and working of =3.60 true strain is moreover executed drawing of about 8 to 12 degrees. In this way, an extra thin steel wire for a steel code having =0.4mm diameter and =400kgf/mm2 tensile strength can be manufactured.