Pressure welding of corrosion resistant metals by cold extrusion

Abstract

Pressure welding of different metals by cold extrusion to produce bimetallic workpieces is a very interesting process, because the properties of these bimetallic workpieces are a combination of the best attributes of the individual components. High annual damage and economic losses as a result of corrosion processes render it promising to choose to a greater extent corrosion resistant metals as structural materials. On the other hand, cold pressure welding is problematic due to the tendency of these metals to build up oxide layers immediately after surface cleaning. The technological application of this research is the production of bimetallic workpieces of different corrosion resistant metals of high strength and surface quality by cold extrusion processes. In the first of the experiments, cold pressure weldings of commercial pure titanium Ti 99.9 and the aluminium alloy AIMgSi1 were produced by forward tube extrusion (FTE) and backward cup extrusion (BCE). In the second stage, the material combination of the β-titanium alloy TiAl3V8Vr6Mo4Zr4 and the austenitic stainless steel X2CrNiMo1812 was cold pressure welded by an FTE process. In all the cases, the quality regarding the strength of the bimetallic workpieces was determined by tensile tests. One objective of the research was to optimize the tribological systems of the extrusion process to obtain workpieces of high surface quality. Further experiments on the binding mechanism confirmed the adhesion theory. As a new method to prepare the surfaces to be welded, the application and use of a thin PVD layer of copper alloy was successful. By this method it is possible to reduce the time for the preparation of the individual components before pressure welding by cold extrusion.