Resistance brazing technology and brazed joints’ properties of pure aluminum conductor

Objective Material and joint structure of pure aluminum conductor winding in motor, as well as inherent characteristics of brazing pure aluminum, were combined to solve technical difficulties of resistance brazing of pure aluminum conductor in atmosphere. Methods Taking Zn-Al alloy as metal skin and cesium fluochlorate as flux core, brazing flux-cored piece was developed jointly with brazing material manufacturers. Taking brazing flux-cored piece as the prefabricated filler material, brazing flux-cored bar as the manual auxiliary filler material and resistance brazing as a joint connection method, brazing experiment was carried out. According to conductor size of pure aluminum conductor used in motor winding and characteristics of product structure, brazed joints of pure aluminum conductor were designed. After brazing, visual test, macroscopic metallography, Vickers hardness, surface brazing rate, tensile properties, DC resistance and current temperature rise were measured. Results Visual test results of brazed joints met requirements of ISO 18279 B. Test results of joints’ line brazing rate in macroscopic metallography and area surface brazing rate of joints’ lap area met requirements of ISO 18279 B greater than or equal to 80%. Average Vickers hardness of brazed joints was 57.8 HV0.1. Average tensile strength of brazed joints was 60.59 MPa, which was slightly lower than that of base material 63.08 MPa. Average DC resistance of brazed joints was 353.64 μΩ, which was slightly lower than that of base material 354.93 μΩ. Average current temperature rise of brazed joints was 117.2 ℃, which was slightly lower than that of base material 117.5 ℃. Conclusion Resistance brazing of pure aluminum conductor for motor winding in atmosphere could be realized by using 0.3 mm Zn-Al flux-cored brazing piece as the prefabricated filler material and \phi 2.0 mm flux-cored bar as the peripheral filler material. Comprehensive properties of brazed joints could meet the design and process requirements.