| 摘要 |
PURPOSE:To obviate generation of a twist, etc. and to improve productivity by using plural grooved rolls which are different in the length in parallel parts on both sides of each groove, and rolling a blank material while exerting a rolling force only on the part of the blank material to be worked to a small thickness in the parallel parts successively from the grooved rolls having the narrower parallel parts. CONSTITUTION:Rolls 3, 5, 7 consist of a pair of flat rolls and rolls 2, 4, 6 are constituted of grooved rolls 21, 41, 61, one of each of which has a groove part 9. The parallel parts 22, 42, 62 on both sides of the groove parts 9 of the rolls 2, 4, 6 are made successively longer from the roll 2 toward the roll 6. Thereupon a blank material 1 is passed between the rolls and is rolled by the rolling force exerted only on the part of the material 1 to be worked to a small thickness successively from the rolls of the set having the narrower parallel parts, whereby the width in the thin walled part is gradually widened. The part of the material 1 positioned in the groove parts 9 of the rolls 21, 41, 61 is buckled and deformed into the parts 9 in the stage of each rolling. |
