Effect of gap on void formation during copper alloy brazing

Abstract

Voids are generally formed when spreading a molten brazing filler metal into gaps owing to such factors as the brazing conditions and flux. In previous studies, it was confirmed that the gap affects the shape of the void, but it is not known in detail how much the gap size is related to the void ratio. Therefore, the purpose of the present study is to investigate the influence of the gap on the void formation more in detail.

Using C3604 as a base metal, two specimen shapes and six gap sizes were prepared. The specimen was heated in an electric furnace, X–rays were irradiated onto the side surface of the test piece during the temperature increase, and a video was taken. In addition, a gap was made using C3604 and glass, and the flux behavior during the heating process was observed. Based on the results of the X–ray transmission test, it was found that the void ratio increased as the gap size was decreased in the range under 300µm. Observation results during the heating process showed that the bubble of boiled flux was increased in number and decreased in size as the gap size was decreased. From these facts, it is thought that the behavior of the flux is changed by changing the gap, thereby changing the void ratio.