Welding Aluminum, GTAW 1

[Capntom]

I am helping a friend repair some aluminum racks that hold donuts. I am using 4043 Aluminum filler that is 3/32 dia. Base metal is .125 thick channel. 3/32 Dia Tungsten that is 2% Thorium. Tonight I am changing to Lanthanated. I grind away the oxide layer with a disk grinder, Al-oxide paper. I am welding with AC, high frequency on continuous, straight Argon 15 CFH. I can't seem to get the bead to flow and look nice. It balls up and looks sooty like the end of a cigarette. Contamination is high prior to me cleaning, oxide as well as food particles. I am also questioning whether I am cleaning enough. The racks do have other areas that were welded so I know it is a weldable alloy. Help??

 

[TVP]

Alcotec has a great deal of information on their website about welding Al. The surface preparation does not sound adequate to me. Check out the following links for more info:

http://www.alcotec.com/psdiff.pdf

http://www.alcotec.com/psgtaw.pdf

 

[stanweld]

Pure tungsten or zirconiated tungsten electrodes should be used with AC GTAW welding of Aluminum. Ball the tip to provide a spherical tip.

 

[swall]

This is a longshot, but I saw it once. The welding rod had centerline inclusions, nearly continuous and this created a dirty looking weld deposit as well as a dirty appearance on the melted rod end. So if all else fails, try switching to another batch of rod.

 

[stanweld]

Disc grinders can produce enough heat to create oxides - not remove them. Better to use flapper wheel with alumina or zirconia abrasives or use power wire brush with stainless steel brushes. Again be careful not to overheat. If you filler metal wire is contaminated, similarly clean them.

Are you using welding grade Argon? If not do so. You may also wish to increase your gas cup size and increase Argon flow rate.

 

[21121956]

Hello everybody:

Capntom, take a look to this site:

http://www.alcotec.com/atras.htm

Good luck !

 

[ctmtwilliams]

It is quite possible that you problem is the oil from cooking the donuts has caused contamination. So you may need to clean the fryer grease off the rack before you can weld it. I would try a non-residue type of solvent to clean with, maybe even something like a spray brake cleaner. Then brush with a stainless steel brush that hasn't been used on anything but aluminum. I weld Aluminum with 2% Thoridated tunsten all the time, Zirconium (even 1%) is a more stable of an arc, but 2% Thoridated works and yeilds a quality weld. You don't need to ball the end, it will happen on its own after a while from the DC+ side of the AC wave.

 

[gtaw]

Don't overlook the material used to make your grinding wheels and flapper wheels.

You are trying to remove aluminum oxide. Don't use aluminum oxide to remove the same. You will imbed the oxide into the surface on which you are trying to weld. Aluminum oxide has a melting point greater than 3200 degrees F while that of the base metal is on the order of 1200 to 1400 degrees F. Use silicon carbide as one alternative to aluminum oxide abrasives. Carbide rotary files (burrs) are also an alternative to consider. You will want to use a "Vixen" type that is made for soft materials such as aluminum, copper, or brass.

Be sure to degrease the aluminum with a solvent such as acetone followed by 90% isopropyl alcohol. Follow the degreasing by removing the oxide before welding. Be sure you clean all your tools with solvent before using them to clean the aluminum. Do not handle the filler metal, base metals, etc. with your bare hands. The oils in your skin will cause porosity.

I agree with one of the other respondents that you should be using pure or zirconiated tungsten when welding with AC.


Best regards - Al

 

[palecactus]

you could also use a little helium mixed as well. but i think that the carbonization is from the embeded foreign material.you may have to use a thin cutting disc and cut through the crack to remove all of the material and replace it with filler rod. then finish it with the flapper. a stainless steel brush would help as well.sometimes you can use heat to chase the oil out of the aluminum.

 

[TravisJoe]

Hello,

How big of a powers source are you useing? whats your ac balance? These are imortant to take note to. .125 isnt that thick so you should be ablet to turn up your cleaning action which will help to get rid of oxides. grinding isnt probably the way to go with cleaning it. try useing scotch bright buffing pads on a 4-1/2 or 5" grinder. that cleanes it up pretty nice and leaves a smooth finish much easier to wirebrush off remaining oxides. for best results wire brush just before you weld. and if you really need to just run a arc arcross the join once with no filler and wire brush right after. the cleaning action will break up crud on the surface. note that changing the ac balance to more cleaning you are putting more heat on your tungsten so you should use non pure electodes. Thoriated is good but gets jagged, and it also has some health risks. lanthanated is my favorite and it balls ok.

Hope that helped

 

[Capntom]

I am using a Miller Synchrowave 180 SD. There is no AC balance, or none that I can find. Can somebody help me locate it??? They do not have a manual either. The machine is a 2003 model that was hardly ever used. I have been somewhat successful welding in new gussets on clean surfaces. I have determined that trying to route out the cracks and re-weld is futile, too much contamination. Oxides as well as greases. I have been using Ø 3/32 Lanthanated and it appears to hold up OK. I am using full pedal at 180 Amps. This weekend I will be experimenting with different cleaning methods. Thanks for all of the Help so far, Merry Xmas

 

[deanc]

Couple( or so) years back used to do service calls for a couple of donut chains and a mexican food chain. Tons of fun but the perks were good at the donut shops.

Anyhow this is what I found.

1.Clean your parts with acetone
2.Heat them good and hot with a torch,cook all the nasties out.
3.SS wirebrush,perhaps grind, and solvent clean again,per post of gtaw.
4.Use Zirconiated tungsten,ball on a piece of clean copper.
5.Use helium
If you grind,your welding supply store will have special wheels for Al. If you draw black smoke,grind out,reheat and clean again.

Free donuts/coffee are required.