Shielding gas issue

[form_change]

At work we weld the same Al assembly at two different sites. Everything is more or less the same except that one site uses pure argon and the other uses a mix (27%He, 73% Ar). The plant using the mix has problems getting the welds to meet specification, where as the one with the pure gas does not. The sections are 5xxx series and essentially a bracket is being welded to a thicker section.

Without getting into details (because that's about all I know at the moment), can anyone suggest any possible ideas why the mix might be giving problems (porosity etc) that would not occur with the pure

I think I'm about to be dumped in this one so I'd like to at least be able to sound like I might have a clue or two...

Michael

[KINGWELD]

Why have the added expense of the Ar-He mix?
Sounds like straight Argon is working just fine(which it will on 5000 series aluminum).
You didn't say how thick each part is, but if it welds fine with straight Argon then that is something to look at.
Adding Helium to the mix makes for a hotter arc and being lighter then air means you will use more then you would with Argon(heavier then air).
Hope this sheds some light for you.

[form_change]

There's an "us" vs "them" attitude between the two plants. Changing gases was mooted before but was defeated along political lines. I can get a change if I can show that the gas is the problem but otherwise no - all the qualification has been done at the respective plants with 'their' gas and their methods (although to the same drawing)
The materials are quite thick - over 3/4". This is multipass welding here.

Michael

[Willy]

The plant using the mix has problems getting the welds to meet specification, where as the one with the pure gas does not.

The evidence pretty well speaks for itself.

Changing gases was mooted before but was defeated along political lines.

If they think politics is more important than meeting specs...well what can I say?
I must be missing something here.
If politics is more important than quality you must have one hell of a supervisor!
I don't envy you.

[macona]

Might be gas contamination. I have even seen it in bulk situations.

The helium should never cause porosity.

[form_change]

Willy, I'm just the guy from quality who gets dumped into these things when it gets too awkward for the wimps who should be making the hard calls (I'm not impressed with how the place is run but until I have something to go to...)

Thanks Macona. As far as I can see the gas is the major difference. The drawings are the same, the weld plan is the same. Both weld procedures have been qualified. I haven't yet seen the power supplies so don't know how they compare. However before I can say that the welders aren't up to snuff (especially as I don't weld for a living myself), all the other things have to be ticked off. I'm still hoping that someone will say something like "make sure you're not using 5183 filler with the mixed gas, as it can cause problems". Hope is a wonderful thing.

Michael
(Did I mention this had been dumped on me?)

[derekm]

At work we weld the same Al assembly at two different sites. Everything is more or less the same except that one site uses pure argon and the other uses a mix (27%He, 73% Ar). The plant using the mix has problems getting the welds to meet specification, where as the one with the pure gas does not. The sections are 5xxx series and essentially a bracket is being welded to a thicker section.

Without getting into details (because that's about all I know at the moment), can anyone suggest any possible ideas why the mix might be giving problems (porosity etc) that would not occur with the pure

I think I'm about to be dumped in this one so I'd like to at least be able to sound like I might have a clue or two...

Michael

Has it ever worked to spec on the mixture?
if it has, what has changed? the welders, machinery, gas supplier, filler rods,...?

[Willy]

Willy, I'm just the guy from quality who gets dumped into these things when it gets too awkward for the wimps who should be making the hard calls (I'm not impressed with how the place is run but until I have something to go to...)

Michael, don't get me wrong, I sympathize with your situation.

It would seem an easy fix to at least try the 100% argon at the location now using the mix, even if only for a bottle or two.
It would eliminate the most glaring difference. If no change in quality is noted then it is either operator or equipment related.

I agree with Macona, the helium/argon mix should not by itself be an issue. Good welds are made with both. For thick aluminum plate I would give a slight preference to the mix because of it would tend to demonstrate less chance of gas entrapment, although the 100% argon would have a cleaner appearance visually.
But obviously there is either a procedural or equipment difference.

[bobhdus]

Like everyone else has already said, if this procedure at one time welded fine then you have to look at the idea that something in your process has changed. Even something simple like position or feed of the gun (push or pull). We "push" our Aluminum welds. New style nozzle causing gas turbulence can draw in oxygen, or even too little or too much gas flow or dirty material. Being that Helium/ Argon gas mixes weld hotter at lower welder settings, it is sometimes used by older shops that don't have enough power or large enough welders to weld the material. Besides soot, if the weld beads are not uniform or defined, they may have set it up as they would Argon and are getting too hot. These are just things to look at. It may also be none of the above. Let us know what you find. Thanks

[BigMike782]

What about weld prep?
Is one plant doing something the other is not or vice versa?