| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an extrusion die with which a mandrel ring is stably fixed in the axial direction, in the extrusion die in which the mandrel ring is externally fit to a mandrel. <P>SOLUTION: The mandrel (30) for forming the inner surface of an extrusion material, has the mandrel (32), the mandrel ring (40), a ring-shaped spacer (50) which is arranged at least on one side of the upstream side or the downstream side of the mandrel ring (40) and a pressing member (37) which is arranged on the top of the mandrel (32). The thermal expansion coefficient (α<SB POS="POST">1</SB>) of the mandrel (32), the thermal expansion coefficient (α<SB POS="POST">2</SB>) of the mandrel ring (40) and the thermal expansion coefficient (α<SB POS="POST">3</SB>) of the spacer (50) have the relationship of α<SB POS="POST">2</SB><α<SB POS="POST">1</SB><α<SB POS="POST">3</SB>. The die is set so that a clearance (S1) is present between the mandrel and the mandrel ring (40) at ordinary temperature and the total dimension in the axial direction of the mandrel (32), the mandrel ring (40) and the spacer (50) is set so as to be equal to the dimension of the mandrel (32), or exceeds the dimension of the mandrel (32) at the die temperature at extrusion. <P>COPYRIGHT: (C)2012,JPO&INPIT |
