| 摘要 |
PROBLEM TO BE SOLVED: To conduct forging in one cycle and to eliminate deburring by forging by using a fully enclosed die formed so as to absorb flowing-out of a stock due to plastic deformation corresponding to a steering rack shape to be formed after the stock is heated to a temp. suitable for warm forging. SOLUTION: A lower die 4 is constituted so that a groove shaped stock accommodation part 40 to shape the outer circumference of a steering rack is formed in the longitudinal direction and a flowing-out absorption part 41 to absorb flowing-out of a stock due to plastic deformation is formed to a prescribed position of the stock accommodation part 40. The flowing-out absorption part 41 is formed in conforming to a tooth form formed by an upper die, i.e., corresponding to the recessed part having a rack tooth form, in aligning to the position where plastic deformation of the stock is generated and in a different shape. The flowing-out absorption part 41 is formed to three stage recessed parts 42, 43, 44 having different height of bottom faces. By this method, flowing-out of the stock due to plastic deformation is surely absorbed to prevent plastic change in the peripheral direction from generating burrs.
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