Lack of penetration on AL

[Gavin Melville]

For some time I have noticed I'm not getting full penetration on aluminum tube.

The settings;
200+Amps AC, 25% Cleaning (or 75, Kempii is backward here), 120Hz rounded squarewave.
12 LPM Argon, electrode 2% lanthanated 2.4mm. Filler Rod 4043, cleaned of course.
Aluminum is 6261 - slightly stronger version of 6061. Cleaned. Tube is 25 x 5mm.

The side faces were bevelled, the fillet joint not. I've tried gapped, bevelled, plain, plain gapped. All the same.

Yes - I did have a little oopsie and dipped the electrode. The electrode is running OK, tip kinda rounded, purple when cooled. The puddle looks OK, no cracks post weld. Some small bubbles in the weld after "disassembly".

The problem is that when I had to take some frames apart I noticed the penetration wasn't very deep. To get them apart you have to beat the daylights out of it ie. it's not really lacking strength. By day lights I mean big vise, 4lb hammer, many strikes.

Any thoughts ?

 

[MattH]

Are you doing any preheat?

 

[hotrodder]

^^ This. Preheat will also help with regards to the porosity. If the tungsten is turning purple then need to increase postflow time although that's obviosuly not gonna effect the weld itself, just tungsten life
Personally i'd turn the AC frequency down (lower frequencies are more efficient at getting heat into the part) and bevel the flat side a chunk more. By the looks of things the fillet sides have LOF at the root, preheat should help that as should lower AC frequency

 

[Gavin Melville]

No. Some of the test jig frames would be awkward to preheat. I'm starting to wonder if it's just bad practice, I'm creating two puddles and bridging them, rather than dissolving filler into one puddle.

 

[Gavin Melville]

I'll try some preheat today on a test piece.

 

[hotrodder]

I'm creating two puddles and bridging them, rather than dissolving filler into one puddle.

That's always gonna result in LOF even with preheat

 

[Gavin Melville]

It is however quite strong. Took a lot of breaking. LOF?

 

[MattH]

Lack of fusion.

 

[Hood]

I am with hotrodder regarding the frequency, I tend to do 4-6mm mainly with my Tig and I like the frequency at 70 or below.

 

[Hood]

12LPM on the argon is also quite high, wonder if that could also be a factor with the porosity?

BTW I am no expert so.....

 

[Gavin Melville]

12 LPM on a size 7 gas lens.

Higher frequencies - say 250Hz, and square-ish waveform seems to tighten the arc and give more penetration. The noise however drives me up the wall.

120 Hz seemed a happy medium. I will try lower.

 

[Brad93]

Loads of problems going on there.

First off cut 15mm off your tungsten with a grinder then regrind a point. If you've touched down you've contaminated it.

You're probably holding too long an arc hence not getting fusion at the root.
Bridging the gap is never gonna work.

Gas is too high. Depending on your cup size you will be chilling the pool and possibly drawing in air.

I preheat my box section usually.
Porosity can be an issue. The reduction in strength is roughly proportional to the cross sectional area of porosity. Obviously there is too much in your welds currently but the odd pore isn't an issue.

You're cleaning is quite low. Try 30% EP and ensure your materials and filler wire are free of oil, grease or contaminants. Easiest way to do this is wipe with acetone.

I think a lot of this is a technique issue.

 

[Brad93]

12 LPM on a size 7 gas lens.

Higher frequencies - say 250Hz, and square-ish waveform seems to tighten the arc and give more penetration. The noise however drives me up the wall.

120 Hz seemed a happy medium. I will try lower.

Waayyy to much gas for me personally. Drop that to 7lpm.

Higher frequency does narrow the arc, and some people will argue with this, but it doesn't actually increase the penetration how you would think like with DC. Lower frequencies put a lot more heat into the pool. 80 would be a much better number for them joints.

It's all about the arc length

 

[hotrodder]

Higher frequencies constrict/tighten the arc improving the depth to width ratio of the weldpool. This is not the same as increasing penetration. Lower frequencies are more efficient at heating things i.e. everything else being equal you'll get a single weldpool more quickly which in turn will help fix the LOF and so on

 

[Brad93]

Hotrodder has just nailed it. The real world results can be seen in one of the latest weldingtipsandtricks videos. Testing this on a rotator.

 

[Gavin Melville]

I'm heading into work shortly, will try these suggestions.

 

[Gavin Melville]

I'd love to see a weld from somebody who knew what they are doing broken apart?.

 

[Brad93]

I'm heading into work shortly, will try these suggestions.

You work nights?
I'll weld some box tomorrow. Only have 2"x2"x3/32

 

[Woody.v8]

You work nights?
I'll weld some box tomorrow. Only have 2"x2"x3/32

He's in NZ

 

[Hood]

I'd love to see a weld from somebody who knew what they are doing broken apart?.

That rules me out then