Welding aluminum alloys

[Mowjunk]

A friend brought an aluminum hand truck to me to weld a broken bracket on it. I noticed it was all riveted or bolted. Someone had tried to weld it before with a mig gun, but that weld looked very, very porous and the weld had broken. I told him I didn't think it was a weldable alloy but he figured he had nothing to lose and asked me to try anyway.

After cleaning it, I tried using tig and it popped a lot and I could tell right away that it wasn't going to be a good weld. Is there any way to tell if an alloy is weldable or not without trying it? This looked like it was either cast or extruded. It had no welds on it for the actual construction purpose which led me to believe it was not a weldable alloy. Any thoughts or ideas?

[Hobart Expert Rock]

MOWJUNK...........YES THEIR ARE A MULTITUDE OF ALUMINUMS OUT THERE, JUST LOOK AT ALL THE GRADES OF ALUMINUM WIRE THEIR ARE.............NEED TO KNOW THE KINDS OF GRADE YOUR WELDING.................THAT IS TOUGH UNLESS YOU TALK TO THE MANUFACTURER YOU WILL HAVE A HARD TO DIFFICULT TIME OF IDENTIFYING THE GRADE OF ALUMINUM.................... I KNOW OF NO EASY WAY.............................ANY ONE ELSE..............ROCK
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[Arbo]

I guess they call it "POT" metal for a reason.

[Guest]

I almost always use 4043 wire to weld Aluminum castings...there are poor quality castings that have junk in them, but you can usually get a weld on them if they're not too bad. Pot metal not to be confused with aluminum, is weldable too, with Aladin rod. It has a lower melting point than aluminum, and quite often has junk in it, too. You are using AC, to weld it, too, ain't ya Mow?

Oh yeah, I almost forgot...aluminum is by nature porous, not as we think of it being porous, but that it will hold moisture, even in drawn bar and extrusions....a little fact that most folks don't know. I have had to heat up blocks to get the moisture out. Try it...heat up a block of aluminum, and watch the water come to the surface....weird!

[Mike Sherman]

There are several aluminum alloys that are not weldable. The strongest ones are not. I believe you made the correct diagnosis based on it's construction and the application.

[Mowjunk]

Thanks to all for the replies.....

I had used my machine on real aluminum before and didn't have this trouble. It didn't look good from the start. And when it started popping, the first thing I checked was to see if I was on AC.

Thanks for the information......I shouldn't say I welded it - more like I stuck it together. But, man, was it UGLY

Thanks again - it's great to have a place like this to come to for answers!

[grocery_getter]

unweldable aluminum

Mowjunk, dont feel too bad. One day last month a gent came to my workshop and asked me to weld 1x1x1/8" square aluminum brackets to an aluminum box. The aluminum box are good, but the brackets are BAD. When I started heating up the bracket after prepping it and it starts smelling really bad and it doesnt want to wet easily. I did about half an inch of it before I told him that I'm not going to continue unless he let me source some weldable aluminum to repalce his BAD ones. The smoke smells really stink. It smells close to that of galvanized steel smeel. You know the kind that makes your tongue taste funny for the next 2 days. To this day I have no idea what aluminum alloy that was. It is aluminum alright but must have some sort of really strange deep coating/ cladding on it.

[Mowjunk]

Yep, now that you mentione it, it did stink and it made a good bit of smoke. I had cleaned up pretty good, but I still had my doubts. It must have held because I didn't hear from him again. A lesson learned!