| 摘要 |
PROBLEM TO BE SOLVED: To obtain an aluminum or aluminum alloy plate having a crackless bent part not easily cracked in a simple method and to provide a manufacturing method of an aluminum or aluminum alloy plate having good bending workability. SOLUTION: A coining part 4 is formed to a bending part, ahead of bending, in a plate material 3 forming an outer material of an automobile panel material. A plate thickness decreasing rate in coning is 10-50% as thin as a thickness before the coining process, preferably 20-40%.
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