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.
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.
To produce electric resistance welded pipes using high-strength steel sheets, it is very important to accurately predict the amount of springback in roll forming processes. In this study, the three-dimensional deformation behavior of sheets at a single bending stand consisting of vertical rolls with a circular profile is investigated in detail using the static-implicit finite element program Marc. The calculation results are in good agreement with the experimental results. The amount of springback in roll forming processes is much smaller than that predicted by the theoretical analysis of plane strain bending. It is found that the small springback is due to the reduction in bending moment caused by tensile deformation in the circumferential and longitudinal directions followed by compressive deformation in the circumferential direction in the later stage of roll forming processes.
In recent years, ultrafine and precise products have played a key role in improving the performance of machines and equipment. In particular, ultrathin wires are expected to be used as a material with versatile functions. Wire drawing using hole dies has conventionally been used in the manufacture of thin wires. In conventional drawing, many dies with a specified hole diameter corresponding to each target diameter of the wires used are needed. With the recent trend of miniaturization, such dies have become difficult to manufacture. The authors have proposed a new drawing method in which a wire is drawn between two concave rolls at a skewed position. Although the efficiency was verified for a wire of 1.0mm diameter, the method has not been applied to wires with diameters of less than 1.0mm. In this research, the method was used on wires with diameters of 0.2 - 1.0mm using the same tools designed for wires with a diameter of 1.0mm. A series of the finite element analyses were carried out as a feasibility study, followed by experimental verification. Results showed that the new drawing method has a very wide range of free-size drawing from 0.2 to 1.0mm diameter even with the use of only one set of tools.
The formability of quenchable steel sheets in hot stamping was improved by preventing the decrease in the temperature of the flange portion of a formed cup. The effects of forming speed on the distributions of the temperature and wall thickness of the formed cup were examined in an experiment on hot drawing with a hemispherical cylinder punch. The decrease in the temperature of the flange portion caused by contact with a die and a blankholder was prevented by high-speed forming using a mechanical servo press. Thus formability was improved by decreasing the drawing resistance of the flange portion. To improve formability in low-speed forming using a hydraulic press, a spacer thicker than the blank was inserted between the die and the blankholder. The decrease in the temperature of the flange portion was prevented by decreasing the extent of contact with the die and blankholder owing to the gap generated by the spacer. In addition, the quenching of the flange portion was prevented by generating a gap to facilitate the trimming of the flange portion.