In this paper

the resistance brazing of pure copper plates with different overlapping areas made under different electrode pressures was studied by ultrasonic testing and metallographic testing. The magnitude and the uniformity of the applied electrode pressure are the key factors for the brazing rate to meet the requirements and the welding quality to be stable. Under proper electrode pressure

the resistance brazing of pure copper plates with different overlapping areas can obtain ideal brazing rate. The results of ultrasonic inspection and metallographic examination of the brazing seam show that the unfused defects with small local weld gap are the main defects in the brazing seam whose average width is less than 78 μm

while in the brazed seam whose average width is over 78 μm

the main defects are looseness and round holes formed by the unfilled solder. The ultrasonic flaw detection is consistent with the metallographic testing

so the ultrasonic flaw detection can be used to effectively detect the brazing rate of large-area overlapping resistance brazing.