Wettability of Brazing Filler Metals on Copper and Copper Alloys

Abstract

The possibility of alloying can not be avoided at the interface between molten brazing filler metal and base metal in brazing, so the wettability of brazing filler metal can not be easily explained theoretically. We used the original apparatus for wettability test and investigated the relation between the wettability of brazing filler metals of Ag-P-Cu and Ag-Cu-Zn-Cd systems on copper and the silver content in brazing filler metals, one between the wettability and the test temperature, one between the wettability and the atmosphere, and the wettability of brazing filler metals of Ag-P-Cu systems on various copper alloys without flux.
The conclusions are as follows:
1) As to the wettability of brazing filler metals of Ag-P-Cu systems on copper, the wettability of BCuP-2, -6, -3 and -4, which contain less than 6 percent of silver, make little or no difference and that of BCuP-5, which contains about 15 percent of silver is excellent. As to the wettability of brazing filler metals of Ag-Cu-Zn-Cd systems on copper, the wettability of brazing filler metals containing from about 12 to 50 percent of silver increases with silver content in brazing filler metals and that of LAg-67Cd, which contanins more than 50 percent of silver decrease on the contrary.
2) The wettability of brazing filler metals of Ag-P-Cu systems without flux in air atmosphere is less than the one and in carbon heater and in argon gas. The wettability of brazing filler metals of Ag-Cu-Zn-Cd systems with flux is not affected by the kind of atmospheres at all.
3) The wettability of brazing filler metals of Ag-Cu-Zn-Cu systems on 6/4 brass in about 50 percent more than the one on copper.
4) As the test temperature rises, the wettability of each brazing filler metal increases.
5) Brazing filler metals of Ag-P-Cu systems wet copper, 5 percent phosphor bronze and 8 percent phosphor bronze without flux, but do not wet common copper alloys except them.