Aluminium advice needed

[Rrobson]

Aluminium isn’t my strong point when it comes to tig, however I can get two bits to stick together although I don’t have a pedal so dont have a lot of adjustment. However a pedal is something on by list of things to buy.
Anyway, what I am really struggling with is welding small round parts to other items (which are usually much bigger) for example, yesterday I needed to weld a 25mm ish x 5mm threaded disc to a length of folded 4mm plate. Although I managed, it certainly wasn’t pretty and I found attempting more than a sixth round at a time usually ended in disaster, mainly issues with being out of position and finding somewhere suitable to prop. In the past I’ve tried welding small round fittings (an style weld on) and had nothing but heartbreak. Yes they stick but are usually not air tight, and are normally a bit of a mess. I know practice is a large factor but any other advice? And when attempting some of these jobs I’ve always done a pre-heat on the larger part (couple of hundred degrees with a propane torch) to try and make life easier.
For info I’m using a jasic 200a ac/dc and I’m familiar with the incompatibility of some of the grades.
Thanks in advance

 

[ukracer]

Aluminium isn’t my strong point when it comes to tig, however I can get two bits to stick together although I don’t have a pedal so dont have a lot of adjustment. However a pedal is something on by list of things to buy.
Anyway, what I am really struggling with is welding small round parts to other items (which are usually much bigger) for example, yesterday I needed to weld a 25mm ish x 5mm threaded disc to a length of folded 4mm plate. Although I managed, it certainly wasn’t pretty and I found attempting more than a sixth round at a time usually ended in disaster, mainly issues with being out of position and finding somewhere suitable to prop. In the past I’ve tried welding small round fittings (an style weld on) and had nothing but heartbreak. Yes they stick but are usually not air tight, and are normally a bit of a mess. I know practice is a large factor but any other advice? And when attempting some of these jobs I’ve always done a pre-heat on the larger part (couple of hundred degrees with a propane torch) to try and make life easier.
For info I’m using a jasic 200a ac/dc and I’m familiar with the incompatibility of some of the grades.
Thanks in advance

Photo might help the experts.?

 

[Brad93]

Aluminium isn’t my strong point when it comes to tig, however I can get two bits to stick together although I don’t have a pedal so dont have a lot of adjustment. However a pedal is something on by list of things to buy.
Anyway, what I am really struggling with is welding small round parts to other items (which are usually much bigger) for example, yesterday I needed to weld a 25mm ish x 5mm threaded disc to a length of folded 4mm plate. Although I managed, it certainly wasn’t pretty and I found attempting more than a sixth round at a time usually ended in disaster, mainly issues with being out of position and finding somewhere suitable to prop. In the past I’ve tried welding small round fittings (an style weld on) and had nothing but heartbreak. Yes they stick but are usually not air tight, and are normally a bit of a mess. I know practice is a large factor but any other advice? And when attempting some of these jobs I’ve always done a pre-heat on the larger part (couple of hundred degrees with a propane torch) to try and make life easier.
For info I’m using a jasic 200a ac/dc and I’m familiar with the incompatibility of some of the grades.
Thanks in advance

Don’t preheat past 100/125 you’re into the realm of overheating most aluminium alloys.

 

[Brad93]

What you’re describing really is a lap joint.
Concentrate your arc about 60-70% at the bottom joint, the flat sheet. Use a third hand or other clamp to make sure you’ve got a tight fit, gaps don’t like to join in lap joints. The issue will come from the top piece, the round part, getting too hot.
A tight arc is essential.
You’d probably want 1.6mm filler.

a part 25mm in diameter is not going to be easy to get more than a ¼ of the way round before your arc length is affected. You can try attacking it from above, you may find you get further round.

clean the edges of the disc with a file to bright aluminium. A wire brush of the flat aluminium sheet, if permissible, wouldn’t hurt.

 

[Rrobson]

Thanks for that Brad, that’s basically what I’ve been doing. Without measuring the temp I wouldnt be able to say what the temp was, enough to boil some water off easily so definitely over 100, maybe around 150.
In that particular example the discs were quite contaminated (basically an old punch machined to size with a tapped hole) even after thoroughly cleaning so that wouldn’t have helped. There were a couple of small tee fillets also and they went in fine. The discs also overlapped the edge so some of it was almost a butt joint. Unfortunately I never thought to take pics...

 

[Rrobson]

Concentrate your arc about 60-70% at the bottom joint, the flat sheet. Use a third hand or other clamp to make sure you’ve got a tight fit, gaps don’t like to join in lap joints. The issue will come from the top piece, the round part, getting too hot.
A tight arc is essential.
You’d probably want 1.6mm filler.

this is exactly what I was doing, around 130amp which was a little cold to start with but ample once warm, and too hot occasionally. The ac arc is such a tricky thing to control, I had to be careful otherwise it would jump up onto the disc and overheat it

 

[Brad93]

this is exactly what I was doing, around 130amp which was a little cold to start with but ample once warm, and too hot occasionally. The ac arc is such a tricky thing to control, I had to be careful otherwise it would jump up onto the disc and overheat it

Amps are too low. Try 160/180. Get in and get out.