Optimizing the Ag Filler Metal Content on Brazing of Cu-Stainless Steel Pipes Joints for Carbon Dioxide Refrigeration Plants

Abstract

A carbon dioxide refrigeration plant is characterized by reaching maximum temperatures in the order of 150 ℃, and maximum pressures in the order of 130 bar, which means that the materials used in the pipes, as well as the connections, must present high resistance, so as not to cause disturbances in the refrigerant fluid. To make these connections, brazing and TIG welding are the processes normally used in copper-copper, copper-carbon steel, and copper-stainless steel connections, optimizing their parameters, in order to create defect-free joints. In this work copper-stainless steel joints were produced by brazing, using brazing alloys with differing silver contents, 56% and 34% respectively. The microstructure of the produced joints was analyzed and characterized, evaluating the influence of silver content on joints’ quality. It was concluded that the joints obtained by using a brazing alloy with lower content of silver presented less defects and an overall better quality.