| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel wire having high strength and excellent in practical fatigue resistance, its production, a steel cord using the steel wire, and a pneumatic radial tire. SOLUTION: The steel wire is a carbon steel wire containing 0.78 to 0.86 wt.% carbon, having fine pearlitic structure in the surface layer part of steel wire, and having 0.10 to 0.40 mm diameter of steel wire. Further, the tensile strength TS of the steel wire satisfies TS>=2350-1450×log d [where TS means tensile strength (N/mm<2> ) and (d) means the diameter (mm) of the steel wire]. Moreover, the total number of times of torsion until, after the steel wire is twisted by previously determined times, a detorsion crack is initiated in the steel wire at the above times is regulated to >=20 (times/100d). This steel wire can be obtained by previously subjecting a carbon steel wire, containing 0.78 to 0.86 wt.% carbon, to blackbody treatment, prior to solution heat treatment of the wire, and applying rapid cooling to it to the extent that no abnormal structure is generated before pearlitic transformation.
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