Research on typical defects of Cu/Fe dissimilar metals vacuum welding-brazing and improvement measures

Abstract Cu/Fe dissimilar metals are joined by welding-brazing in a vacuum furnace, and then typical defect formation mechanisms of the post-welded joints are observed and analyzed. As a result, it has been found that the major welding-brazing defects are elemental segregation, solidification cracks and poor fusion. It is worth noting that the causes of element segregation and slag inclusion are related to high welding-brazing temperature, impurity of raw materials, inadequate cleaning of materials before welding-brazing and volatilization of impurity metals in the chamber of the vacuum furnace. In addition, welding-brazing defects such as poor fusion and solidification crack are not only related to elemental segregation and slag inclusion, but also to other external factors such as excessive cooling rate and minor furnace leakage, etc., and the defects tend to occur at the interface near the Cu/Fe joint connection. By changing the welding-brazing process, it can effectively inhibit elemental segregation, reduce the slag inclusion and avoid poor fusion, solidification cracks and other interfacial welding-brazing defects, and ultimately obtain a good combination of copper and iron dissimilar metal joints, the shear strength has greatly increased compared to before improvement.