Aluminium welding troubles

[backpurge]

Almost got it with the venturi idea.

Enough turbulence in the flow will allow air in no matter the position...

Slightly high flow (a few percent) is far better than too low, but there's a threshold that once passed means you might as well just shut the gas off because it's only going to get worse - especially once psychology is taken into account (I keep turning it up and it's not getting better )

It's quite a common problem, more so with MIG, you'd be surprised how much a relatively small amount of spatter build up in the gas nozzle can disrupt the gas flow, the welder starts getting porosity so turns the gas up and it gets worse so we get the phone call "your gas is crap" etc, etc

 

[TechnicAl]

It's quite a common problem, more so with MIG, you'd be surprised how much a relatively small amount of spatter build up in the gas nozzle can disrupt the gas flow, the welder starts getting porosity so turns the gas up and it gets worse so we get the phone call "your gas is crap" etc, etc

Or its your wire.......

Dont know if its been said but Aluminium will oxidise over a couple of days, especially damp days, so it may need cleaning again.....and that could be the part or the wire or both.

 

[Soundstorm]

Well there you go. A sheared gas line will certainly cause the issue. No gas at all. This is different to a conventional leak. A slight leak doesn’t stop your gas flow from being sufficient but it can cause air contamination effectively giving you a partial active shield.
In your case it’s all irrelevant as you’ve found the issue.
Now you’ve got the ball ache of removing all that porosity before going forward. No easy task tbh and I doubt you will ever get those areas to weld perfectly clean again as it’s Pretty nasty and penetrating right in. you didn’t exactly stop at the first sign of trouble.

Yup, would have been better to stop trying. But those welds were actually combinations of various starts and I went over them to try and 'clean it up'.
Luckily not a big issue. This part was way over-engineered, I welded the fillets on the other side without a problem, and it's holding up nicely.

With the repaired hose I notice gas coverage is way better, so the hose was probably already leaking somewhat, but I still had barely enough gas to cover the welds. Good lesson, will keep an eye on it in the future.

 

[Instructor_Nige]

That there is simple contamination in my humble opinion. once the tungsten tig gets contaminated you will get results like this until you remove the contamination.. grinding a fresh point is not enough as the contamination is often further back. you need to snap off the effected part of the tungsten and start with a freshly ground point.. to avoid contamination in the first place ensure you have the correct AC balance, 30% is usually good, and more and you risk contaminating the tungsten with ali being sucked up by too much cleaning action, also keep the end of the filler rod within the shielding gas, a common mistake with people is to pull the filler wire in and out of the shielding gas forgetting that the end of the filler wire is subject to the effects of oxygen in the air while its molten if not protected by the shielding gas. hope this helps

Nige