| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a tube expansion plug.SOLUTION: A tube expansion plug is used for a tube expansion process of a heat transfer tube which is composed of aluminum or an aluminum alloy and which has a plurality of inner surface fins formed in the inner peripheral surface. The tube expansion plug comprises a shaft part and a head part which is formed on the tip side of the shaft part, has a bombshell shape and includes in the outer periphery, an inclined groove inclined to the longitudinal direction of the shaft part. The inclined groove has a groove depth of 0.05 mm-0.5 mm and a groove width of 0.05 mm or more which is narrower than an apex part width of the inner surface fin. A distance between grooves adjacent to each other is 0.05 mm-1.5 mm, and an inclination angle of the inclined groove to the longitudinal direction of the shaft part is 10°-85°.</p> |
