| 摘要 |
PURPOSE:To produce a pipe having inside grooves with a simple apparatus by carrying out a drawing with a floating plug and a split die, forming grooves with a grooved-plug and a transfer roll and finally reducing the diameter with a finishing die when the grooves are provided inside the metal pipe to increase the surface area. CONSTITUTION:The split die 10 provided on the outer circumference of the metal pipe 1 of a material is closed, drawing operation is performed between said split die and the floating plug 3 inserted into the metal pipe 1 and, then, the split die 10 is opened, the floating plug 3 is moved in the drawing direction to be brought into contact with the position of a supporting die 5. At the same time, the grooved-plug 7 mounted on the tip end of a tie rod 6 connected with the floating-plug 3 is brought into contact with the position of the transfer roll 8. The grooves on the surface of the groovedplug 7 is pushed by the revolving compression of the transfer roll 8 to the inner surface of the metal pipe 1 to reduce the diameter of the metal pipe 1 and simultaneously to provide grooves 11 on said inner surface and finally to reduced by the finish die 9 into a pipe having inside grooves of prescribed diameter.
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