BRAZING PROCESS

BRAZING PROCESS

Brazing is a process of joining metals with a non-ferrous filler material. The filler material has a melting point above 427°C but below the melting point of the parent metals to be joined. The filler material is called “spelter” in case of brazing and it must wet the surfaces to be joined. 

In brazing, the joint has to be carefully designed and joint prepared with due care. When spelter is molten, it flows into the joint clearances by capillary action and fills up all vacant spaces. Since higher temperatures are involved in brazing, a light alloying action at the surface layers of parent metal takes place. This lends considerable strength to the brazed joints. 

Brazing may be done with the help of oxyacetylene brazing torch, or the heat may be produced by induction/eddy currents. Sometimes electric furnaces are also used. 

Common brazing filler materials are silver, copper, copper-zinc, copper phosphorous, aluminium silicon and copper-gold alloys. These alloys are avaiable as wires, rods, preformed rings and in powder form. Brazing temperatures usually range from 427°–1200°C. Fluxes commonly used are borax, flourides and chlorides of potassium, sodium and lithium.

Most common example of brazing can be seen in brazing of H.S.S. and tungsten carbide tipped tools.