2012 年 53 巻 622 号 p. 993-997
Two types of die, i. e., open and semiclosed, were used in forward extrusion forging under four lubrication conditions: a) no lubrication, b) phosphate coating with metallic soap, c) cold forging oil, and d) a combination of b) and c). When the amount of reduction in area R was 22%, extrusion forging to the final shape was possible with both dies and under all lubrication conditions and extrusion speeds. At a low speed of 0.017 mm/s, the semiclosed die allowed a lower load and was more effective under steady-state conditions than the open die. On the other hand, at a relatively high speed of 0.17 mm/s, the open die showed lower loads both at the early stages and under steady-state conditions, and resulted in fewer bulges. Extrusion forging was easier with the open die than with the semiclosed die. The combination of phosphate coating with metallic soap and cold forging oil enabled extrusion forging to R = 26% and markedly decreased the load. However, when pins were inserted into the lower parts of either the open or semiclosed die in order to limit extrusion length, load increased, making it difficult to carry out extrusion forging.