The Welding Mechanism in Drawing of Aluminum Sheet

Abstract

As a continuation of the previous report which dealt with a mild steel sheet, this study covers the welding phenomena at a tool-work interface in deformation processing of aluminum sheet which has been investigated experimentally by using a two dimensional drawing-type friction testing machine. Variation mode of the frictional coefficient during the drawing process can be classified into four types, namely,- constant, increasing, decreasing and waving type. In both the increasing and decreasing types, the welding occurs at a die exit portion, similar to the case of mild steel reported previously. In the waving type, a process of growth and the peeling away of the welding layer is repeated at a central portion of the die, and corresponding frictional coefficient waves develop. The frictional shear stress on the welding region is constant (about 68.6 MPa), approximately equaling the yield shear stress of the aluminum. The ability to repair the welding has been examined by measurement of the frictional coefficient at the designated drawing travel for mineral oils with various viscosities and compositions.