| Summary: | 碩士 === 南開科技大學 === 車輛與機電產業研究所 === 99 === In cold precision forging from steel billets, a very high forming pressure is required because of the high flow stress at room temperature. The high pressure leads to result in fracture of dies or decrease of the service life of the dies. Therefore, it is important to reduce the forming pressure in cold die forging. In this paper, a method employing an axially freely floating container in the precision forging process is proposed. By freely floating the container, the material flow may be controlled positively by utilizing the frictional force over the billet-container interface so that the billet material may flow easily into the die cavity in the two direction of combined forward/backward extrusion. A series of simulation on the combined extrusion under four kinds of container movements such as fixed, single direction driven, single direction with constant stroke driven and freely floating containers ware carried out by using the FEM program DEFORM 3D. The influence of the four different kinds of container movements on the forming load, die stress, material flow and the maximum effective strain of products are examined. The results in the study reveal that the forging load and the die stress could be decreased most by employing the floating container.
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