WELDING OF DISSIMILAR METALS

Abstract

In heat exchangers, tubing is required for the passage of the working fluid throughout the heat exchanger circuit. The requirement of the tubing inside the heat exchanger is of high heat transfer rate, thermal conductivity and ductility. For this purpose, Copper tubes are being used in the industry because they serve the above requirements optimally. But due to economic constraints their usage throughout the heat exchanger circuit is not profitable. For the rest of the tubing outside the heat exchanger, Stainless Steel tubes are used because of economic considerations and good corrosion resistance. Therefore replacement of copper components by stainless steel can be an attractive way to overcome the difficulty. There are different methods to weld copper with stainless steel and these are arc welding, diffusion bonding, laser beam welding and electron beam welding. Literature survey indicated that limited work has been reported on welding of dissimilar metal (copper with stainless steel) by gas tungsten arc welding method. GTAW offers many advantages such as it is relatively inexpensive, it offers an inert gas atmosphere at the weld using argon gas, which protects the weld pool from reacting with oxygen. This results in a more successful weld, the welding process is compatible with most product designs and so it offer flexibility. The equipment is relatively easy to use. The above reasons led to attempt weld copper with stainless steel using the GTAW process in this project.