| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus and a method for manufacturing an internally grooved tube, by which occurrence of double-bulging when the grooves are formed is reduced and the quality of the tube is improved. SOLUTION: In the apparatus 2 for manufacturing the internally grooved tube, a ball rolling part 4 has a plurality of stages of ball groups 41A, 41B for pressing the metallic tube 1 to the grooving part 31 in different positions in the axial direction in a portion corresponding to the grooving part 31 of one grooved plug 3. In the ball rolling part 4, the diameter r1 of the ball 41a of the ball group on the upstream side in the drawing direction of the metallic tube 1 is set larger than the diameter r2 of the ball 42a of the ball group 42A on the downstream side. COPYRIGHT: (C)2011,JPO&INPIT
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