Behavior of Cadmium on Brazing

Problems Associated with Fumes

Abstract

The production of fumes during brazing is a well-known phenomenon. One of the most important problems associate with such fumes is cadmium due to this element's hazardous nature.
In the present work, the behavior of cadmium fumes during brazing was closely examined for BAg-1 and BAg-3, the typical silver filler metals containing cadmium.
The conclusions drawn from the experiments conducted are as follows:
1) The amount of fumes produced by either BAg-1 or BAg-3 was found to increase as the heating temperature increased when the optimum brazing temperature range was exceeded. This phenomenon can well be explained by the secondary electron images obtained by EPMA.
2) For the both types of filler metals, the cadmium contents of the fumes produced remained as low as less than 0.80% and 0.70% for BAg-1 and BAg-3, respectively, when brazing was conducted at a heating temperature within the optimum temperature range. When this range was exceeded, however, the cadmium content of the fumes increased as the temperature increased.
3) For this experimental device, so long as the heating temperature was kept within the optimum brazing temperature range, Cd concentration of fumes in the air can be controlled less than the WES (9007) control limit. When this range was exceeded, however, the fume concentration surpassed the WES limit by an amount which increased in proportion to the temperature employed.