AC tig problem on aluminium

Starting with the hard stuff eh? I can think of five things that can cause trouble right off the top of my head:

-Low quality casting: Very likely, aluminum castings usually vary from bad to horrible in terms of porosity and contamination. It might just be a low quality casting.

-Not heating the piece well enough: Novice aluminum welders do this all the time. If things aren't going the way you think they should it might just be that you aren't getting the work hot enough. You have to lean on the pedal a lot more and a lot longer than you think.

-Wrong filler approach: The combination of the very hot arc and the low melting point of aluminum makes it difficult to add filler without it melting and oxidizing first. Try coming in from from a different direction or angle.

-Inadequite shiedling gas / contamination: Always a consideration. Make sure you have good flow and no leaks in the line. Your local careless welding store may have also given you bad gas but that's less likely.

-Incorrect filler: I've seen several different people pick up and use stainless filler in aluminum on several different occasions. This probably isn't your problem, check it anyway.

Andrew Bish> having a problem with tig welding aluminium

From the problems you are having sounds like you may be better off heating the weld area, and wire brushing until the surface of material is free from impurities, then welding using 4043 rod.

Nothing to offer, but here is my bad story on welding aluminum.

I am a self taught tig welder. I've noticed steel is much easier to weld than aluminum. Anyhoo, I wanted to stick together heavier alum pieces than I ever tried. A section of 3/8 x 1/2 bar onto a 3/16 plate. Total penetration and strength were not important, so I figured I could do it.

I clamped the bar onto the plate with a couple of small steel spring clamps. I tacked the weld in a few places and all seemed to be going ok. Started welding along the length. Ok, maybe not the prettiest weld but it'll hold. As I approached the last few inches of weld I noticed that I was moving much faster that I ever had before. In retrospect I should have backed way off on the pedal. As I got to the last part where the spring clamp was still holding the tacked pieces, the whole end of the bar piece melted and collapsed under the force of the spring. Arrgh! Obviously too much heat.

I cut out the last inch-and-a-half or so and got a new piece welded in.

Job successfully accomplished eventually, but I obviously am a long way from being a competent aluminum welder.

In actual fact when you are used to it, welding aluminuin is in my view easier than steel!

As with any form of welding though, close control of the amount of heat you are putting into the job is very very important, and this is the main reason why a beginner needs plenty of practice, after getting a good idea of the basic techniques.

hey hey, if I had that practice I wouldn't be a beginner. One more lesson the hard way.

Try to get more practice controlling the heat, as if you are having difficulty with that then you will find it very very hard to get good results with TIG welding process.