HOLLOW SHAPE MATERIAL FORMING EXTRUSION DIE

摘要

PROBLEM TO BE SOLVED: To provide a hollow shape material forming extrusion die capable of improving fatigue durability.SOLUTION: An extrusion die 10 includes a male mold 20 for forming an inside shape of a hollow shape material 1 and a female mold 30 for forming an outside shape of the hollow shape material 1. The male mold 20 has a holder 25 formed of a fitting hole 25C and a spider 22 fitted into the fitting hole 25C. The spider 22 is formed of a mandrel 23 corresponding to the inside shape of the hollow shape material 1 and a plurality of bridge parts 24a to 24d protruded outward from the outer circumferential surface of the mandrel 23. An inner circumferential surface 25D of the fitting hole 25C is shrink-fitted to a tip surface 24C of each bridge part 24a to 24d. An interference between the inner circumferential surface 25D of the fitting hole 25C and the tip surface 24C of each bridge part 24a to 24d is 0.4 to 0.6% of an inner diameter of the fitting hole 25C.SELECTED DRAWING: Figure 2