Q&A for How to Weld Aluminum

TIG (Tungsten Insert Gas) welding is commonly recommended as the preferred method. TIG welding provides precise control over the welding process and produces high-quality welds on aluminum.

Generally aluminum is viewed as being harder to weld than steel, but the processes are different and aluminum also requires some different equipment as well. You probably shouldn't expect to do a flawless job on your first project.

You need a push-pull system or a wire feeding system for your MIG welder (like spool gun or "cobra head").

During the positive half cycle, there is a cleaning action (which is good), but it also means most heat goes into the tungsten electrode (which is bad). Only use as much cleansing action as you need. It is normal for the tungsten to form a ball end from this heat. If it is burning too much, reduce the amps or use a thicker tungsten.

All welding is arc welding. If you mean, "Can I use a stick welder (SMAW) to weld aluminum?" the answer is yes, although most professional welders would not do it this way.

T.I.G. stands for tungsten inert gas welding. T.I.G. machines rely upon a high-frequency (RF) pilot arc to establish the welding arc.

No, only AC TIG is designed to weld aluminium.

The perfect environment for welding aluminium is an area covered in sand. Sand is useful because if you heat it, it will not explode like concrete.

The grade depends on many characteristics of the metal. The grade should also be based on the finished product's use, not ease of welding.

Alternating. During the positive period, the surfaces are cleansed, which is pretty necessary for aluminium. During the negative period, more heat goes into the pool. Most modern TIG welders let you control the relative proportions of positive and negative electrodes.

AC or DC depends upon what electrodes (filler metals) you are using. Their requirements will be specified on the packaging.

Yes, by a specialist welder. Aluminium is difficult to weld, and an engine block is subject to considerable forces.

It's possible, but very difficult to get a good-looking result. You're better off with soldering/brazing. It's not as good electrical connection (assuming that's what you're after), but it looks better.

Molten aluminium is highly reflective. If you see a shiny spot form under the arc, it's molten, so it's time to start the bead.

Weld a test piece, then do a bend test on it. A good weld bends without cracking.

The AC setting is generally used for welding aluminium and magnesium, whereas the DC setting (usually DCEN) is used for welding various steel alloys such as mild steel and stainless steel, nickel, copper, and titanium, among other metals and alloys. It is mentioned to get a TIG welder with AC capability in addition to DC, as most cheaper welding TIG welding machines will only have a DC setting, making them unable to weld aluminium unless other methods are used.

That depends on what you are welding and what forces it will be under (e.g. impact? twisting? bending? pulling? etc.). If strength is critical to a structure or the safety of persons (e.g. a car, trailer, roof, etc.), the advice of a professional welder, manufacturer, engineer, or otherwise adequately skilled and experienced person should be sought. If the strength is not critical and not a safety issue (e.g. a table or gate), then you could likely strengthen it by adding an thicker aluminium frame and bolting, welding, or riveting it together. It really depends on the application and what is to be strengthened.

It depends on how you welded it; when MIG welding, particularly tack welds, can look "welded together" when they are in fact not, try weaving a little between the pieces. When TIG welding aluminium, fusion TIG welds (done without using filler) have a tendency to crack , simply use filler. Also make sure you are using the correct electrodes/filler/mig wire, etc..

Yes, by using aluminium arc welding electrodes, however this isn't really recommended for thin aluminium and is quite tricky to use - practice on a few pieces of aluminium similar to your work piece to get the hang of it before you start welding.

Possibly. You would need some specialist advise and practice on other similar/identical metal "transfer cases" to get some welding practice in, but ideally, purchasing a new transfer case would definitely be the recommended solution, most welders/mechanics/engineers would probably advise against welding automotive cases back together, as the case may likely just crack and fail again at the weak point of the weld (which is the area on either side of the "toes of the weld").

Depends on how thick, and what the application is - for thick aluminium in strength critical settings, most aluminium welders usually recommend "preheating" the metal (e.g. with an oxy acetylene torch) so the puddle flows, and fuses better, and a better weld is created.