抄録
While the porthole die extrusion has been widely used in manufacturing hollow products, die manufacturing including die designing has been still dependent on the expert's skill and trial and error practice. Although detailed understanding of die pressure in extrusion is essential to systematic die designing and also leads to more correct results of finite element analysis, the experimental research for die pressure in porthole die extrusion has hardly been found. In this study, in order to investigate the distribution of die pressure in porthole die extrusion, pressure sensor which has lots of concentric serration was used. Pressure sensors were placed on the faces of dies (core and cap), before extrusion starts. The die pressure was examined at two different extrusion stages: the one was just after division process was completed and the other was during steady state. Just after division process was completed, the highest pressure area on the core existed in the vicinity of the porthole near the center. In steady state, pressure gradient was very large in the area between the porthole and die edge, and the pressure around the central part was lower on the core. Besides, the pressure decreased from outside to die exit on cap.
