| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject steel filament with high fatigue resistance so designed that surface residual stress lies on compression side and compressive residual stress is uniformly distributed both circumferentially and longitudinally and, furthermore, the surface residual stress is corrected. SOLUTION: This steel filament is such one that surface residual stress lies on compression side and compressive residual stress is uniformly distributed both circumferentially and longitudinally, wherein it is preferable that respective residual stress values measured at >=8 points situated at equal intervals along the circumference of this steel filament fall within the range: A±0.15×A (A is the average value of the respective residual stress values) and the compressive residual stress value is <=-10 mm, which is defined as the flex magnitude at a point when a filament flex comes to a maximum after a semicircular portion of the steel filament 10 cm in length is coated with a lacquer in its longitudinal direction followed by conducting an etching in an aqueous nitric acid solution, provided that the stress value is set as 'negative' when the filament is bent on the etched side, or 'positive' when the filament is bent on the lacquer-coated side. |
