| 摘要 |
PROBLEM TO BE SOLVED: To exceedingly improve the fatigue resistance of a steel wire subjected to heat treatment after wire drawing by controlling the increase of the proof stress after heat treatment compared to the proof stress before heat treatment to the one above a specified ratio. SOLUTION: A steel wire obtd. by wire drawing of a steel wire rod is subjected to heat treatment at a low temp. in a short time to increase the proof stress after heat treatment by >=5% compared to the proof stress before the heat treatment. This >=5% increase of the proof stress is important. The reason is that, in the case repeated input above the certain one is applied to the wire, on the topmost surface of the wire, fine cracs caused by local plastic deformation are generated, and, after that, they expand and grow to destruction. To the plastic deformation in the topmost surface, the higher the proof stress is, the higher the resistance is made, by which the plastic deformation is made hard to be generated to improve its fatigue strength, and by increasing it by >=5%, a precise difference appears in the fatigue strength. Moreover, advantageously, the stee wire has a steel compsn. contg. 0.6 to 1.0 mass% C, and the diameter is 0.05 to 4.0 mm. |
