Abstract: A steel wire, 0.10-0.40 mm in diameter, obtained by subjecting a high-carbon (0.70-0.90 wt. %) steel wire material to heat treatment and wire drawing, wherein its tensile strength and test values of special repeated torsional tests satisfy a predetermined relation; and a method of manufacturing the same. A high strength steel wire which has so high a ductility as to substantially prevent the wire from being broken even during wire twisting, and which rarely encounters a decrease in the ductility even after the wire has been subjected to age hardening by heating, is obtained, and a method of manufacturing the same is economical.

Abstract: A composite rubber body is formed by embedding steel cords in rubber and vulcanization-building them. In this case, each of the steel cords is a single steel filament wire or plural twisted steel filament wires obtained by drawing of a wire rod of high carbon steel having a given composition. The filament wires satisfy given relationships between filament diameter and tensile strength before and after the vulcanization and have a retention of loop strength of not less than 55%.