| 摘要 |
PROBLEM TO BE SOLVED: To improve the strength of a decorative hole of a disk for a car wheel without degrading any design. SOLUTION: This method for forming the decorative hole of a disk for a car wheel comprises a step of pre-forming the decorative hole for punching the hole of the diameter slightly smaller than that of the shape of the final decorative hole, and a step of smoothing and reinforcing a sheared surface 2c and a fractured surface 2d generated by pre-forming by ironing a stress- concentrated part at least in the vicinity of a corner part of the pre-formed decorative hole 2 by an ironing punch 10 and a die 12, and partially increasing a plate thickness to form a thick-walled part 14 by moving excess material 14 generated by the ironing to a stress-generated part in the vicinity of the corner part, and these steps are performed successively.
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