MIG Brazing, Cast Iron and Aluminium
MIG Welding is great for steel, but often Arc or TIG would be a better choice for other materials. But If MIG is all you have then you are in the right place. These pages suggest ways of welding aluminium and cast iron with a basic MIG welder. I've also experimented with MIG brazing wire in a welder that isn't designed for the job just to see if it can still be useful.
Aluminium welding can be frustrating until you de-bug your welder. The wire is much less stiff than steel wire so is prone to crumple after the roller. An oversized tip and plastic wire liner are required together with other tweaks to your welder.
How to weld aluminium (turns out it's not so bad).
Aluminium very quickly forms an oxide layer which needs to be removed before welding. From there the welding process is tricky because of the rather narrow window between melting the aluminium and blowing holes.
MIG brazing is a relatively new technique that tends to be used by automotive manufacturers on modern steels that can't really be welded using conventional techniques.
The material is intended to be used with specially developed MIG welders, though it can be carried out with a standard MIG with some loss of benefit. The page suggests a technique and includes a strength test.
A very useful application of MIG brazing wire is in the repair of cast iron. Braze is much softer than steel filler wire so reduces problems with cracking of the cast iron.
This page describes a traditional studding technique as well as the use of braze to join a cast iron gear casing, and discusses alternative methods that could have been used to join the casting.