Abstract
Three kinds of extrusion-type friction tests were performed to evaluate friction shear factors at different kinds of extrusion dies, or at the backward extrusion punch. The first kind is a forward rod-backward can extrusion type friction test for evaluating friction at a taper die. The second kind is a new friction test based on forward rod-backward can extrusion with a conical die providing projections. The third kind is a friction test based on combined forward- backward straight can extrusion. The third kind was modified to evaluate friction at the bearing of a backward extrusion punch quantitatively. The lubricity of conversion coating lubricant for low-carbon steel, the lubricities of conversion coating lubricant and various viscosity mineral oils for aluminum alloy were evaluated. The lubricities of the different lubricants were compared for each extrusion type. Surface expansion ratio does not always affect friction shear factor directly. The lubricity of conversion coating is almost the same for each extrusion type. On the other hand, the lubricity of mineral oils is markedly affected by the extrusion type. In the case of extrusion in which oil is difficult to retain, the lubricity decrease, and adhesion occurred.
