饼状柱形齿轮一步精密成形及其改进

Precision forming by one-step and its improvement for pie-shaped cylindrical gear

为解决采用常规闭式模锻工艺一步成形饼状柱形齿轮精锻件固有的镦压力大和角隅难充满等问题,重点介绍了近期出现的基于集成开放成形、分流成形和推过整形等两步/多步成形的合理成分,并以改变模腔形状为手段的扩隅凹模成形。该成形方法通过扩大难填充的凹模下角隅及临近区域空间,使得镦压阶段能够有较多金属流至临近角隅并占据部分扩隅空间,得到下角隅体积足够但形状欠规整的中间状态半成品,再通过倾斜的扩隅侧壁对变形金属解除了局部约束,降低了镦压力;而体积足够但形状欠规整的角隅被顶出时,受倾斜侧壁的作用,流入扩隅空间的金属流向下角隅,完成下角隅填充。柱形齿轮和柱形内齿轮的试验情况表明,在保证角隅充满的同时,镦压力降幅达50%以上。扩隅凹模成形可以在常规装备条件下协调解决看似矛盾的降低镦压力和改善角隅填充的问题。

In order to solve the inherent problems of high upsetting pressure and difficulty in filling corners for precision forgings of pie-shaped cylindrical gear formed in one-step by conventional flashless die forging,the recently proposed enlarged-corner cavity die forming by changing the shape of die cavity was emphatically introduced based on the reasonable composition of two-step/multi-step forming processes,such as integrated opened forming,divided flow forming and push-through shaping.The forming method enlarged the space of bottom corner and adjacent area of die which is difficult to fill,so that more metal flowed to the adjacent corner and occupied part of the expanding space in the upsetting stage.Then,the intermediate workpiece with sufficient volume of bottom corner and less regular shape was acquired,and the local constraints on the deformed metal were relieved by the inclined enlarged-corner side wall and the upsetting pressure was decreased.When the corner with sufficient volume and less regular shape was ejected,the metal flowing into the expanded-corner space flowed to the bottom corner to complete the filling of bottom corner due to the action of inclined side wall.The test results of cylindrical gears and cylindrical internal gears show that the upsetting pressure drops by more than 50%while ensuring that the corners are full.Thus,the seemingly contradictory problems of dropping the upsetting pressure and improving the corner filling can be solved in coordination through the enlarged-corner cavity die forming under the condition of conventional equipment.