| 摘要 |
PURPOSE:To raise remarkably a forming limit of a curl height by combining the primary process of a pierce burring and the secondary process of a compression ironing. CONSTITUTION:In a pierce burring working of the primary process, a burring prepared hole is punched by a pierce die hole 12 provided on a fixed pierce burring punch 13, and a pierce punch 10 fixed to the center of a burring die 11. Subsequently, a flange 15c which is larger than a diameter of a prescribed fin hole is formed by the burring die 11 and the pierce burring punch 13. In the secondary process, by an ironing die 17 and an ironing punch 18 of a diameter of a prescribed fin color hole, an ironing working is executed by setting an ironing rate so that a flange height 16d of a prescribed curl height is obtained with regard to the flange 15c.
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