Friction welding process is a solid-state welding process where heat is imparted to the work pieces by mechanical means via the frictional rubbing of the mutual pieces together under a load and accompanied by deformation of the parts. Generally, in friction welding of steels, plasticity for forging in both components will be attained in a narrow band of temperature.
However, this is not so while welding diverse materials such as Aluminium to Copper. Aluminium melts at around 660 degrees whereas Copper does not even attain plasticity at that temperature (weld happens only when both the metals attain plasticity). Further copper is so conductive that the heat generated at the interphase gets conducted away very fast resulting in a lower temp on Cu.
Another challenge is oxidation. Cu oxidizes differently at different temperature levels. At lower temperatures it forms a thin Cu2O layer and at 200-300 °C CuO forms. Al has a huge affinity for oxidation and it oxidises fast. The first monolayer of oxidation happens almost instantaneously and will be around 1.5nm – 2nm deep. This is one of the biggest challenges that need to be handled during the forging process. Once we take care of these issues, Friction Welding is the best possible option to forge Aluminium and Copper. This usage of Bi-metallic lugs helps prevent galvanic action due to dissimilar contacts.
In friction welding of steels , metallic bonds are generated which impart very good strength to the joint. In copper to aluminium welding, molecular orbital bonding is achieved.
ETA, a pioneer in Rotary Friciton Welding, has developed and delivered Friction Welders to a host of companies for joining Cu to Aluminium. We invite you to talk to our welding experts to see how Friction Welding can solve your joining problems. ETA Technology is in the game to help you make your best product ever.