Tacking aluminum with AC stick?

My experience is that a buzz-box won't work although DC welding is quite acceptable.

As an aside welding 5/16" aluminum is going to require some fairly serious heat if TEG welding and quite a bit of warping will likely be encountered.

-- John B.

Yes, the first one gives me a bit of hope then the second one takes most of it away. He references some very recent threads on the weldingweb forum, so perhaps his research is still on going? I too, thought of the old carbon arc torch method. Had no luck finding examples of it being used with aluminum.

But thanks for the links! I never would have clicked on the Yahoo answers one... No idea why I did not find the other one, it should have been on the first page or two of one of my searches.

Hope someone here can prove you wrong on the first part:) My one and only experience with DC aluminum stick was due to a broke TIG. Had an emergency repair to something and yes it was quite acceptable. Thank goodness looks was not one of the criteria of acceptability that day!

My experience with cast is that it warps quite a bit less than plate. Has plenty of other problems that plate lacks... And yes, I have heard the fan kick in high on a Miller Dynasty plenty of times while welding aluminum.

Try

There is also some sort of "aluminum solder" that was discussed on rec.crafts.metalworking some time ago. If you are just sticking stuff together to try that might work. I believe it is low temperature operation.

-- John B.

I just came across "aluminum solder" see

-- John B.

Dura-fix, Luma-Weld, and a bunch of others are pretty close to straight zinc (check the MSDS). You do have to remember to scrub through the oxide layer once you've got a puddle of molten filler on your base metal, or it won't stick, it's pretty much not like any other process. For small parts, you can get it hot enough with a propane or mapp torch. I've not used it in decades, and even then not for anything structural or critical, mostly just played with it a little. Once upon a time, you could only get them from flim-flam dealers at fairs and such, now you can walk into any home store and find them in the "bernz-o-matic" section. It does oxidise to a darker color than straight aluminum, so repairs are noticable.

I think my biggest concern would be if all that zinc would mess up your later TIG weld? You might get lucky and it could just alloy in as everything gets reheated, but I don't know.

Is the intended use one where you can't use a couple of drilled and tapped holes and a handful of screws to hold stuff together? A hand drill and a tap wrench are pretty simple as long as you stay away from some of the fragile tap sizes like 6-24. It might be less annoying and time consuming than a torch and filler.

If we're already talking about moving away from the stick machine, how about using a spool gun? I know they're not cheap, but a lot of people like the "ReadyWelder" stuff, and you can run them on batteries to get the DC, you don't need another DC source (though it can use one). The manual implies you still need DC for aluminum, though, so I guess still no hooking it straight to your tombstone buzzbox.

--Glenn Lyford

Nice site, thanks. Direct link to SMAW page:

Interesting how this site has completely different advice than yahoo answers above, recommending perpendicular electrode position and a short arc with fast straight travel (correct) vs yahoo advice long arc horizontal electrode position (probably compensation for current or travel speed too low or other bad technique. What is "cross arc" anyhow?).

I have seen structurally sound welds in aluminum made with DC SMAW. None were very good looking compared to GTAW or GMAW done by the same people, but they weren't horrible either. (This was a case where there was a small amount of non-critical aluminum welding on a mostly steel job, not enough to bother shipping a different welding machine to the job site.) SMAW is suitable for tack welding aluminum castings if you can come up with a DC machine. I have never heard of successful use on AC, it is already hard enough with DC.

"Aluminum solder" is zinc or mostly zinc, which alloys readily with aluminum. You can make a weak connection with it with some difficulty (it involves scratching off the aluminum oxide layer under a puddle of flux and molten solder), but there is almost always a better way. If used to "tack" a weldment, the welder would want to remove all of it before welding near enough to melt it. Temporary bars or straps glued or taped on might be easier for the welder to remove.

I have not done extensive aluminum using arc but my limited experience was a fairly short arc, moderate rod inclination and really fast travel. In fact, as I remember it, that was the hardest part of doing it. The deposition rate is something like 3 times that of steel.

-- John B.

Greetings Glen, While you are correct about the aluminum solder being mostly zinc and the necessity of scratching away the aluminum oxide coating under the solder the joint done properly is not weak compared to the aluminum being soldered. Recently I tested aluminum solder for a customer. The solder was Forney brand. I soldered 1/2 x 1/2 x 1/8 angle. After cleaning the aluminum I wet it with the solder and the used a stainless steel brush to scrub the aluminum through the molten solder to insure a completely wetted surface. I "tinned" or wetted two pieces and then sweated them together at right angles, so the contact patch was 1/2 x 1/2. After cooling the angle bent instead of the bond breaking. I tried both twisting the pieces and peeling them apart. In each case the aluminum bent and the solder did not fail. I was frankly amazed. So I know that if the aluminum is properly wetted with the Forney brand solder it will make a joint at least as strong as the aluminum. Cheers, Eric

Have seen rotational molds come back from repair with dark areas where all the big dings had been. Was starting to suspect it was a high zinc alloy but had never confirmed this. Seen similar spots on new molds a few times too.

Suspect you are correct here. Have not tried Dura-fix but did play with some Harris ALCoR a while back. It apparently has a bit more aluminum than Dura-fix (824°F verses Dura-fix's 732°F) and it is flux cored. Had absolutely no luck TIG brazing with the stuff so it is very doubt full I will be able to weld across a high zinc braze.

May give this a try too but it will be tough. Curves and angles that are not exactly 90 degrees. Plus this is a mold so any through holes will have to be filled and re textured to match. Corner blocks with small bolts through the beveled out area that will be welded any way might work...

That sounds like an excellent procedure, I'll definitely try it if a suitable situation arises. I still don't think soldering is is a great way to "tack" the parts of an aluminum weldment prior to welding, because of the nasty behavior of zinc at aluminum welding temperatures, but it could work fine if all of the solder is removed prior to welding within an inch or so of the soldered "tack".

Regards, Glen

Greetings Glen, I wouldn't use aluminum solder for tacking parts that would be welded over either. The zinc would at the very least contaminate the weld. And boy does it fume. Eric