| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a cylindrical metal piece for storing articles at a low manufacturing cost. SOLUTION: A main metal piece is formed in a cylindrical shape having a polygonal flange part 54, and manufactured by cutting a final forged stock formed by the forging (a final forged stock 102) to a predetermined shape. The final forged stock 102 is formed by forging a metal stock 70 through a cold forging process comprising first to sixth steps. The metal stock is forged to represent the contour of the main metal piece in the first to third steps, and the stock is further forged and a hole part is pierced in the subsequent fourth to sixth steps. In the third step, a flange part is formed in advance, and in the fourth step, the metal stock is press-expanded against a flange preliminary forming part 86 in a hole making step to complete the flange part 54. In this final forged stock 102, the cutting amount is reduced more compared with that in a conventional method when it is cut so as to represent the main metal piece, and the manufacturing cost of the main metal piece can be reduced. |
