Etching question

Millerismyname · Wed Jul 01, 2015 1:27 pm

I'm sure someone along the way has asked this question but I'm still going to ask, ha! So the work I do is aluminum Tig, all clean gravy work. Mostly square tubing of various sizes and some small 4" and 5" pressure tanks. All of my work has to be super clean because the products are sold as a premium product. I'm running a weld Tec 20 torch with the quarts set up and a 3/32 tungsten. The question I have is reducing the etching along the weld. I know reducing the en will take some of it away but is there any techniques or specific settings you guys have or use for the reduction of the etching? Any help will be appreciated. The welds are tanks and butt welds and edge welds and pretty everything.

Braehill · Wed Jul 01, 2015 1:37 pm

Miller,
If the pictures you have posted are normal etching for you then you're doing about as good as can be expected and probably better. It doesn't matter how clean or new the Aluminum is you still have to break up the oxide layer to weld it which means you're going to show some etching. Yours seems to be minimal.

Len

Millerismyname · Wed Jul 01, 2015 2:15 pm

: Frame with etching; image.jpg (37.95 KiB) Viewed 1627 times

here's a frame with the etching that really needs to be reduced. We polish all Of the tubing pre weld. So hitting them with scotch bright after looks bad. The welds can't have any penetration or distortion on the backside because we put adhesive strips on all 4 inner walls post weld. So if there's anything bubbling through the strips won't sit flat. Any tips on the etching reduction?

Braehill · Wed Jul 01, 2015 2:28 pm

Miller,
Unless someone knows something I don't know if you reduce your cleaning you will increase penetration. Seems like if you do that you're going to run into problems with push through. If you have an inverter welder then there's some things you can try, but I'll let some of the folks here who use them all the time answer those questions. I'm still old school and use transformer machines.

Len

LtBadd · Wed Jul 01, 2015 7:58 pm

Braehill wrote:Miller,
Unless someone knows something I don't know if you reduce your cleaning you will increase penetration. Seems like if you do that you're going to run into problems with push through. If you have an inverter welder then there's some things you can try, but I'll let some of the folks here who use them all the time answer those questions. I'm still old school and use transformer machines.

Len

As Len was leading to, you can experiment with reducing the cleaning cycle with the AC balance control, and control the penetration with travel speed. Defiantly use only argon (no helium) to help reduce penetration. Even so not sure you'll see a dramatic difference but the results might be improved over what you have now.

You could also use a heat sink on the back side to prevent penetration, I'd suggest copper as it won't stick to the AL if you do burn thru, and the back side will still be flat

Millerismyname · Thu Jul 02, 2015 8:08 am

I have the htp 221, so I do have some features at my disposal. I have tried as much as 85%en but man the puddle gets grainy. I would like to stay in the 72-75%en realm. if maybe I had a practical application for the amplitude setting on the machine I could see if using that helps. Anyone use amplitude?

dave powelson · Thu Jul 02, 2015 11:45 am

Millerismyname wrote:I have the htp 221, so I do have some features at my disposal. I have tried as much as 85%en but man the puddle gets grainy. I would like to stay in the 72-75%en realm. if maybe I had a practical application for the amplitude setting on the machine I could see if using that helps. Anyone use amplitude?

If you can independently adjust the EN, EP amp settings on the htp 221, the below links
may give you some clues:

http://forum.weldingtipsandtricks.com/v ... f=5&t=6391

http://weldingweb.com/showthread.php?45 ... light=zank

Millerismyname · Fri Jul 03, 2015 6:05 pm

That was a great post on amplitude adjustment, when I get the opportunity I'm going to play around with it using what the post outlined. One more question is browning on the backside of sheet metal, specifically .050. Any string recommendations and or causes.

Rick_H · Sat Jul 04, 2015 9:37 am

Stainless sheet metal?

Millerismyname · Sun Jul 05, 2015 3:31 pm

No sorry it's a 5000 series aluminum .050, it just seems like no matter what I do the backside gets browned.

Sun Jul 05, 2015 4:43 pm

Millerismyname wrote:No sorry it's a 5000 series aluminum .050, it just seems like no matter what I do the backside gets browned.

Unfortunately, the oxide layer on aluminum is porous, and can trap traces of lubricant and coolant from the mill, which cooks on the back side. I can dress it out with a wire wheel or a buffing pad, but some applications won't allow this. Perhaps someone here knows an electro-chemical process like that used on stainless?

Steve S

LtBadd · Sun Jul 05, 2015 7:01 pm

Otto Nobedder wrote:
Millerismyname wrote:No sorry it's a 5000 series aluminum .050, it just seems like no matter what I do the backside gets browned.
Unfortunately, the oxide layer on aluminum is porous, and can trap traces of lubricant and coolant from the mill, which cooks on the back side. I can dress it out with a wire wheel or a buffing pad, but some applications won't allow this. Perhaps someone here knows an electro-chemical process like that used on stainless?

Steve S

From http://www.ableelectropolishing.com/all ... /aluminum/

... Unlike stainless steels, you cannot passivate aluminum in order to remove the contaminants on the surface. In addition, there are few options for improving microfinish after machining. Electropolishing is an effective means for providing a part that has an enhanced surface finish and clean surface...

I would like to see aluminum electropolishing

kiwi2wheels · Mon Jul 06, 2015 9:50 am

Depending on the size of your part, perhaps try washing the backside with a hot water / detergent solution and then rinse with really hot water.

The heat will open the pores in the aluminum.

Superiorwelding · Tue Jul 07, 2015 9:18 am

Millerismyname,
Here is another thing you can try that CrummyWelding (Roy Crumrine) showed me. He uses a #5 regular cup to cut down his etching zone. I use a gas lens and thought it is better but in testing, because I didn't believe him

) I ran a gas lens and regular set up side by side and the regular will cut your etching down by half. It does look to me like your tubes have a good look already but I think your "improvement" will show itself in your other welds. Give it a try and let me know how well that worked for you.
-Jonathan

Tue Jul 07, 2015 8:48 pm

I'll back up Superiorwelding's post.

I always get better results on aluminum with a simple collet than I do with a fancy gas-lens.

Steve S

Millerismyname · Fri Jul 10, 2015 7:50 pm

Really? A collet over gas lens, to be honest I've never used a collet I've always gone with gas lens. So a number 5 gas lens cup vs a number five collet cup, the collet wins? What about gas coverage it will be affected in some fashion correct? Let me ask another question, why does the etching zone decrease when I'm welding tanks on a turntable, but then I do a butt weld with the same settings and the etching is twice the size? Travel speed?

dunkster · Fri Jul 10, 2015 8:57 pm

Millerismyname wrote:... why does the etching zone decrease when I'm welding tanks on a turntable, but then I do a butt weld with the same settings and the etching is twice the size? Travel speed?

If you're referring to edge joints, as in your 1st pic, my guess is gas flow is being parted by a 90' joint and dispersing faster than on a butt joint, where gas coverage is a little better due to the 180' of surface area.