反向挤压力计算式的误差分析与实践

Error analysis and practice of extrusion force formulas on backward extrusion

目前 ,用于计算反向挤压力的计算式都是根据相应正向挤压时的算式 ,并直接令作用在挤压筒壁上的摩擦为零得来的。实践中发现 ,计算出的挤压力与实测值差异较大 ,无法正确指导生产。造成这种差异的主要原因是忽略了正、反向挤压时变形区中温升及加工硬化程度不同对金属变形抗力的影响 ,及采用了与正挤压时相同的变形抗力值。通过实验 ,建立了确定反挤压时金属变形抗力的方法及计算式。验证结果表明 ,以此为依据计算反向挤压力 ,误差不大于 5 % 。

At present, the extrusion force formulas used in calculating backward extrusion are all based on the according direct extrusion's, and the friction between the metals and inside of the container is assumed to become zero. In practice, the calculated extrusion force according to these formulas has much difference with the real figure frequently, which can not guide production. The main reason is to neglect the difference of the temperature rice and strain hardening between the direct extrusion and the backward extrusion. Through the experiment, the backward extrusion force formulas were found. The error of backward extrusion force calculated by the formulas is not more than 5%, so it can be applied in engineering calculation.