| 摘要 |
PROBLEM TO BE SOLVED: To provide an extruding die which allows a mandrel ring to be stably fixed to a shaft by setting proper interference and the maintenance of which is simply performed.SOLUTION: A mandrel (30) with which the inner surface of an extruded material is formed has the shaft (32) and the mandrel ring (35) which is fit outside the shaft (32). The mandrel ring (35) is composed of a material whose thermal expansion coefficient is smaller than that of the shaft (32) and the outer peripheral surface (32a) of the shaft (32) and the inner peripheral surface (35a) of the mandrel ring (35) are formed so that a clearance (S) which is narrowed on the downstream side of the extrusion and widened on the upstream side is present between the both (32), (35) at the ordinary temperature in a state where the mandrel ring (35) is fit outside the shaft (32), and the clearance (S) disappears at least on the downstream side at the die temperature when performing the extrusion. |
