What is the difference between 4043 and 5356 alumimium MIG wire?
To put it simply, 4043 MIG wire is an aluminium filler alloy which contains 5% silicone, whilst 5356 contains 5% magnesium. The former is most suited to service temperatures over 150 degrees and the latter is best used for temperatures far below this level of heat – the magnesium compounds which it contains will not stand up to intense temperatures.
The 4043 wire tends to produce more aesthetically pleasing joins, with smoother surfaces, a decreased amount of spatter, and less smut. Yet, it is worth considering the fact that the 4043 wire has a lower level of ductility than the 5356 wire.
Why is aluminium MIG welding difficult?
Aluminium is trickier to weld than steel, as it is very conductive and has a low melting point. To MIG weld aluminium effectively, hold the torch vertically & push away from you rather pull. This will offer a greater opportunity for the argon shielding gas to do it's job & give you a neater looking weld. Typically, you need to increase your wire speed & travel quicker too. Make sure you remove any oxide from your material afterwards with a stainless steel wire brush, rather a steel one, as steel filings from other jobs could contaminate the workpiece.
Changes to Mig set up when welding aluminium.
As aluminium is softer and expands more than metal, it provides feeding difficulties. We strongly recommend that you change your steel torch liner to teflon to prevent sticking and switch the contact tip to the aluminium variety to compensate for expansion. Replacing your V grooved drive rollers with some U shaped ones will further assist feedability. Finally, don't forget aluminium welding demands pure argon shielding gas rather than an argon mix.