对图1所示制件,如果采用顶部镦粗的工艺,因镦粗比太大而难以实现,故选用了图2所示的短圆柱毛坯挤压成形。但锻件顶部会形成一凹坑(如图3所示),这样就要靠加大机加工余量来保证制件尺寸要求,不但浪费了材料,也加大了机加工工时。为此,我们通过试验将毛坯改为图4所示形状,很好地解决了此问题,锻件顶部不再形成凹坑缺陷。 Figure 1 shows the workpiece, if the top upsetting process, because the upsetting ratio is too large and difficult to achieve, so use the short cylindrical blank shown in Figure 2 extrusion. However, a forging is formed at the top of the forging (as shown in FIG. 3). In this way, the machining allowance needs to be increased to ensure the size requirements of the workpiece, which not only wastes the material but also increases the machining working time. For this reason, we have solved this problem by changing the blank to the shape shown in Fig. 4 by experiments, and no pit defects are formed on the top of the forging.