Precision Extrusion Using Tool for Counter Pressure

研究了正向挤压杆件或齿轮、反向挤压筒件或杆件的复合挤压.为了在工艺结束时获得指定的齿轮长度，使用计数器工具控制向前挤压速度。通过控制正挤压速度，在较低的挤压压力下获得了给定挤压长度的产品。1.控制正挤压速度的正-反复合挤压当反压力提高到坯料在应变为1.0时的流动应力量级时，端面变得完全平坦，不需要后加工。2.向前-正反挤压速度交替控制的反向复合挤压由于端面并不总是与工具接触，所以端面不能完全平整。在不控制反向挤压速度的情况下，后端面的平面度为0%，而采用反向挤压速度交替控制后，后端面的平面度可达80%。3.正向齿轮-反向挤压杆或罐与正向挤压速度控制的组合挤压反向挤压杆的情况下齿侧的欠充缺陷小于反向挤压罐的情况。在反向罐的情况下，当反压力变为应变为1.0时坯料的流动应力的75%时，缺陷消失，当反压力为流动应力的140%时，可获得完全平整的端面。反向复合挤压与反向挤压基本相等，反向挤压可获得较长的正挤压件。

Extrusion of forward bar or gear, and backward can or bar by combined extrusion is studied. To attain the specified length of the gear just at the end of the process, the forward extrusion velocity is controlled with a counter tool. By controlling the forward extrusion velocity, a product with given extruded length are obtained with a low extrusion pressure. In this process, the counter-pressure caused at the die exit can be utilized to reduce the defects.1.Forward-backward combined extrusion with control of forward extrusion velocityWhen the counter pressure is raised to the order of flow stress of the billet at the strain of 1.0, the end surface becomes completely flat and no post machining is needed.2.Forward-backward combined extrusion with alternate control of forward and backward extrusion velocitiesSince the end surfaces do not always contact with tools, the end surfaces cannot be flat completely. Although the flatness of the back end surface is 0 % without controlling backward extrusion velocity, it becomes 80% when the alternate control of extrusion velocities is employed.3.Forward gear-backward bar or can combined extrusion with control of forward extrusion velocityThe under-filling defect at the side of teeth in the case of backward bar is less than the case of backward can. In the case of backward can, the defect is disappeared when the counter pressure becomes the 75% of flow stress of the billet at the strain of 1.0, and the completely flat end surface is obtained when the counter pressure is 140% of the flow stress.4.Inverse extrusion after controlled forward-backward combined extrusionAlthough the extrusion pressures for only forward-backward combined extrusion and inverse extrusion are almost equal, the longer forward extruded part is obtained by the inverse extrusion.