Flux - Powder, Easi-Flo
Easy-flo™ Flux Powder is Johnson Matthey’s leading brand brazing flux. It is sold widely throughout the world and is recognised as one of the best flux powders available. It is very fluid at the bottom end of its working range resulting in early and extensive flux spread. This ensures that the joint surfaces are well protected from oxidation at the earliest possible point of the brazing operation. This high level of fluidity also helps to reduce flux voids/entrapment in the joint, the low viscosity of the flux aiding its displacement by the brazing filler metal from the joint gap.
Easy-Flo Flux Powder has a working range of 550-800°C. It is most suitable for use with gold, silver, copper, copper alloys, brass, mild steel and stainless steel, but not aluminium soldering.
Brazing is a metal-joining process whereby a filler metal is heated above and distributed between two or more close-fitting parts by capillary action. The filler metal is brought slightly above its melting (liquid US) temperature while protected by a suitable atmosphere, a flux. Then flows over the base metal (known as wetting) and is then cooled to join the work pieces together. It is similar to soldering, except the temperature used to melt the filler metal is above 450 °C.
Easy-Flo™ Flux Powder has excellent ‘hot rodding’ characteristics and adheres well to a warmed brazing rod allowing flux to be transferred to the joint area via the rod. This characteristic has made
Easy-Flo Flux Powder very popular in hand brazing operations where the time to produce a brazed component is crucial.
Clean and degrease the joint surfaces before applying flux.
Flux powder should be mixed with water and a few drops of liquid detergent to form a thick paste. Paste should then be brushed onto the joint surfaces before assembly. Further flux should then be applied externally on either side of the joint mouth.
Hot Rodding is where a warm brazing rod is dipped into flux powder and the flux adhering to the rod is transferred to the joint area. This is an effective fluxing method but difficult to achieve good penetration of capillary joints. It can be used to supplement a pre-fluxed area during heating.
It is good practice to mechanically clean and degrease the joint surface before applying flux. Heat slowly and evenly to the brazing temperature, without local overheating. Use the flux as a temperature guide - it will become clear or opaque as the brazing temperature is approached. If blackening of the flux occurs this is often a sign of insufficient flux, overheating or flux exhaustion.
The flux residues left after completion of the brazing operation are corrosive and should be removed. The residues for Easy-Flo Flux Powder can easily be removed by soaking in hot water > 40°C for between 15 and 30 minutes. Any remaining residues can then be brushed off in running water.
- Supplied in a 250g tub