| 摘要 |
<p>Disclosed is a tube expansion plug (1) that is used for expanding an aluminum tube (2), the inner surface (21) of which has been supplied with a lubricating oil. The tube expansion plug (1) has a dimple region (11) in a contact region (S) where the surface of the tube expansion plug contacts the inner surface (21) of the aluminum tube (2), the dimple region having formed therein a plurality of dimples, the equivalent circle diameter of the opening of each dimple being 3 µm or greater. The average value (D µm) of the depths of the dimples and the average value (L µm) of the equivalent circle diameters of the openings of the dimples satisfy the following relationships: 2<=D<=100; 10<=L<=200; and L/D<=25. The area percentage of the openings of the dimples in the dimple region (11) is 10-50%.</p> |
