| 摘要 |
PURPOSE:To produce a bar for a heat transmission pipe having projections made into the shape having no chipping on the raised surface by forming the 2nd working roll to a smaller diameter and drawing a work while inclining the work to the 2nd working roll side from the insertion direction thereof. CONSTITUTION:The diameter of the other 2nd working roll 18 is formed to the diameter smaller than the diameter of the 1st working roll 13 having a rugged pattern. A work 11 is rolled by the 1st working roll 13 having the rugged pattern and the 2nd working roll 18 and is then drawn while the work is inclined from the insertion direction 12 toward the roll 18 side. The orthogonal projection of the peripheral speed 14 of the roll 13 with respect to the insertion direction 12 of the work 11 is thus made larger than the orthogonal projection 17 of the rolling speed 16 of the work 11, by which the chipping on the raised surface is eliminated.
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