How do you weld cast aluminum?

[azgorilla]

Any one know much about welding cast aluminum? I am trying to help a buddy of mine by welding a "pinhole" in his cast aluminum rim for his car. I tried to tig it, but it just got worse (reads as: pinhole got bigger), even though I preheated, it seemed that it just would not get hot enough. Then, it just let go, and poof! a big hole about 1/8 inch. He's going to kill me. Can anyone give me a bit of insight? Thanks.........azgorilla

[GaryM]

You are on the right track with preheat.
wheels have some special coating on them so you need to use a really good cleaner then stainless steel brush to clean it.

Anther thing i would try is to use a small drill bit and dill the hole out that will get the scap out of the hole that is casing it not to weld.

That is what i would do. Hope this helps

[Paul Seaman]

Oxidized Aluminum melts at a much higher temp than the base metal so when you get it hot enough to develope the pool it melts into infinity. You have to get it clean, scotchbrite rolocs, and acitone. This is some of the hardest welding to be done.

Good luck,

[azgorilla]

Thanks for the input. I am a novice tig welder and I must be doing something very wrong. I clean everything real well, then SS brush it, preheat, then I start the tig, but here is where the trouble starts. It all just seems to kind of "foam" on the aluminum, then it begins to get sooty looking, all without getting shiney (melting point) so as to add filler. I have double checked my machine settings, argon pressure, but to no avail. When it comes to tig-ing a regular piece of aluminum, not a problem. This rim is driving me crazy!!!!

[dyn88]

are you sure its not magnesium.

[GaryM]

magnesium Welds very closly to aluminum.

I have done some Wheel welding the big ones on semitrucks they get worn out on the beed we build them up and turn them down. There are special coating to keep the aluminum shinny that will not come off very easy even with electric wire wheel or acitone. You really need to clean the **** out of it.

Gary

[azgorilla]

Magnesium.....Hmmmm. Never thought of that. Have no idea how to tell the difference though, other than it being nonferris. It sure shines up on the outside (the side you see when looking at car) just like aluminum. It DID have only a pin hole in it, but not any more. It was at the end of the weld on the inside. The operator did not overlap the beginning of his weld, and left a crater at the stop. I will take everyone's ideas (cleaning, etc) and put them to use and try again. I will be taking the tire off so as to get to the inside of rim. I left tire on so that I would be able to inflate it and check it as I went. Hmmm, so much for that idea. Any one else that can help out or knows anything about welding wheel rims, please post a note........Right now I feel like taking a permanent vacation!

[ASKANDY]

carbide bit grind it out and make sure it's not a Mag wheel. You will need a different filler for that. Still sounds like a cleaning problem or gas purity problem with all the soot and stuff.

A-

[dyn88]

AH HA unless you remove the valve stem you must remove the tire. Once you remove the tire I guarantee you will have no problems after a thorough cleaning. it all makes sense now. just like you cant weld an aluminum box sealed shut. When your trying to weld the pinhole you are applying heat to the rim and subsequently the inside of the tire, As this heat is applied, the gas inside the tire(air if you may) is expanding and poof. When you get a puddle with any sort of penetration it blows out. Ive been here many a time welding aluminum tubing and always forget you must vent the expanding gas. and with this I would like to here if I,m right so let us know what happens. by the way if its a two piece welded wheel odds are its not magnesium.

[gclose]

Identifying Magnesium/Welding wheel rims

To ID. mag. put a drop of spirits of salts onto the surface of metal and wait a few mins . If it turns black its Mag. Hope this helps.
All previous advice good.
Strip rim,drill out hole,remove surface skin(both sides) with Al. cut rotary file/burr, preheat,weld both sides. You wont have any further probs.

[azgorilla]

Happy Camper

Just wanted to up date everyone and thank you for all your input. Turns out that the rim is aluminum and yes, it was a cleaning problem. Took all advice everyone, applied it to the job and wah lah! problem fixed! Thanks again for all the sage advice. I am really a very happy camper!

[dyn88]

its nice to here a thank you. Im glad all worked out in the end. remember aluminum clean clean clean.