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Joining Aluminium
Aluminium is notoriously difficult to join because of its tenacious and very stable surface oxide. Fluxes to remove that oxide are very aggressive and can have a short life.
Because it can be difficult to get sufficient flux into the joint and a lack of fluidity of the molten alloy, the joint design tends to be more "bell shaped" than parallel. The joint is wider at the top where the alloy is fed.
Alusol
is a low temperature flux cored, lead bearing soft solder wire. It is available in 1 metre lengths at 0.9 and 1.5mm dia.
It will readily solder commercially pure aluminium and copper aluminium alloys. It is best heated with a soft propane flame.
Al12Si
is a 12% silicon aluminium rod suitable for general purposes. Use the same principles of brazing to get the best from this alloy although better results are often achieved if the joint is slightly "belled". Because its melting temperature (575 - 585 deg C) is close to that of pure aluminium (620 deg C) care should be taken when heating to avoid melting the surface of the aluminium. The use of propane is recommended. Bring the joint to temperature in 2 - 3 stages, allowing a short period of "soak time" to allow the joint to "soak up the heat". This will help to prevent the components collapsing during brazing. Use it with AlSi Flux.
Technoweld
is more akin to a welding rod and tends to produce fillet joints rather than capillary ones. In simple terms, use a wire brush to clean the joint area, warm it with a propane torch to about 350 deg C, melt the alloy onto the surface, abrade the aluminium through molten Technoweldt to effect the joint. It can also be used to repair cracks etc on aluminium castings or build up studs. To see how to use it, watch the 8 short video clips on www.technoweld-fusion.com.
A pack consists of 5 rods 2.5mm dia x 200
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