Murata MAKOTO (村田 眞)

Circular tube of copper with spiral projections on the inside wall is used for the improvement of the heat exchange efficiency of the heat exchanger. The copper tube is made by swaging. The copper price is expensive and the swaging manufacture speed is late. If the tube is conventionally manufactured by extrusion and made of aluminum, not only the price of tube becomes cheap but also manufacture speed gets faster. And the projection of spiral shape for heat effective exchanger can be made. We modified the traditional extrusion machine and successfully extruded the trial extruded circular tube with many spiral projections on the inside wall. The billet material is lead. We discussed experimentally the influence of shape and the size on the trial extruded circular tube about processing conditions. The established number of projection is 20 and lead angle is 30 degree with the spiral projection on the inside wall of the circular tube. It was possible to extrude established circular tubes with many spiral projections on the inside wall under appropriated processing conditions.