To provide the manufacturing method of a tube with an inner groove capable of preventing breakage of a stock tube in a manufacturing step.
A holding plug 2, a plug shaft 4, and grooved plugs 5a and 5b are disposed inside a stock tube 1. Work rolls 16a and 16b are disposed at positions matched with the grooved plugs 5a and 5b outside the stock tube 1, and backup rolls 18a and 18b are disposed so as to be in rolling contact with the work rolls 16a and 16b. In addition, a sizing die 8a is disposed between the work roll 16a and the work roll 16b, and a sizing die 8b is disposed on the downstream side in the tube drawing direction from the work roll 16b. By drawing the stock tube 1, a tube 19 with the inner groove is manufactured. The ratio R of the peripheral velocity Vr1 of the work roll 16a and the peripheral velocity Vr2 of the work roll 16b to the drawing speed Vt immediately after passing the sizing die 8b is set to be within a range between 1.2 and 5.0.
SAEKI CHIKARA
TATEYAMA TOMOYUKI
