Studies on Impact Extrusion (7th Report). On Cold Impact Extrusion Forces

Abstract

We had investigated the cold impact backward extrusion of metals such as lead, tin, aluminium, and zinc. The extrusion forces and the force-time curves were oscillographically measured by means of wire strain gauge method. The observed results were minutely compared with the one already obtained in static extrusion. The experimental results were as follows: (1) The shape of the impact extrusion force curves changed depending on the materials, but was almost analogous to the static one. (2) The limit of the extruding reduction was about 95% on zinc but 95% or more on lead, tin and aluminium. (3) The impact extrusion forces might become equal or less than the static one, if both the reduction and the rate of extrusion were increased. (4) The influence of the annealing temperature on the extrusion forces of aluminium was proved so remarkable that for blanks fully annealed the force was reduced to less than half of the values for unannealed samples. (5) In the case of zinc, the extrusion force was only slightly increased by annealing.