| 摘要 |
<p>Oxide film formed on a spring-retaining flange by heat treatment gets unlikely to peel off, thereby improving wear resistance of a contact surface of the spring-retaining flange with a valve spring. The oxide film 15 of the part of the spring-retaining flange 3 with the valve spring 7 is at least partially removed to make thickness of the oxide film to 0.00 to 0.02μm.</p> |
