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AirGunEric · Site Admin

I have an aluminum part I need to weld and don't want to FUBAR it up on the first try!

Basically, the aluminum is approximately 3/16" thick and is cracked- so I need to use my MIG welder with .030" aluminum wire to weld it up (Argon/Co² mixed gas). The welder is a smaller 120v Lincoln unit (a WeldPack-10 or maybe -20. I'd have to go look, I've owned it for so long I don't remember anymore!)

Anyways, aluminum generally melts (or outright vaporizes) at much lower temperatures than would steel- and I'm hoping someone would have an idea of approximate amperage and wire speed to weld the 3/16" aluminum- I don't really have space on the broken part to do a lot of "testing" before getting down to business.

In case it affects anything- the aluminum part is a housing for water in a pressure washer where the water source comes in. Seems the person who thought I might fix it left water in it over the winter in sub-zero temperatures- ice expansion cracked the housing.

23ib0d0n · Moderator

I don't like to mig Al. unless it is at least 61 series with a huge heat sink but much prefer that it be 75 series and still use a huge heat sink. If I don't know for sure, then a very knowledgable guy with a tig and a cool tank is more likely going to be where I take it.

If it is 3/16" wall tube then I'd clamp it to the heatsink, fill with a wet bituminous earth or wet ground calcium carbonate inside the tube and use a starting amperage around 30 ~ 35 and find some 0.015" or 0.010" wire to help some with penetration at the lower power levels.

Using tig on such a thin piece of Al. would probably still be safer for the part though. Wink

AirGunEric · Site Admin

I hear what you're saying- I don't think the pressure washer is worth much more than a couple hundred $$$'s brand-new, so the minute someone needs to be paid to repair it or it needs any significant parts (if available) it quickly becomes cost-inefficient. This is a friend's unit- so I need to give it a shot anyways. I don't have a TIG setup and won't likely anytime soon.

The heat sink is a good idea- I'll see what I can dig out to use for that.

23ib0d0n · Moderator

Looked at one of my old welding shop manuals and it stated use pure argon for Al. and for using 0.030" wire, then slow the feed rate to about 230 and begin around 50 amps.

About all I ever use now is smaw and didn't see any of the old mig reels anywhere for the brand name on the light guage wire.

Would an Al. solder be strong enough? Just a thought . . . Mr. Green

AirGunEric · Site Admin

Aluminum solder- that's maybe an idea. I wonder what the melting point of such a thing would be? Assuming something as light-weight as a propane torch- that might work.

I will have to investigate a bit more on this I think...

23ib0d0n · Moderator

The Al. solder I have used was $6/lb at Northern Tool {looks like it is $15 now} and has a melt temp. about 750*f {400*c} however it doesn't flow like a fluxed brass at that temp. and you'll still want to use a huge heatsink.

Alstone · Moderator & Site Supporter

Hi Eric
I've used aluminium solder a few times and found it very difficult to use, the brand over here was Eutectit and required about 400c, on the jobs that did turn out allright you need the part scrupulously clean and very good control of the heat and as 23ib0d0n says a big heatsink, the type I used was flux cored but In found that extra powder flux helped, when things seemed to be going well the whole lot Collapsed. good look.

AL

AirGunEric · Site Admin

Well- I had some time this afternoon so I thought I'd try to repair the housing with the MIG, seeing as that's what I had handy.

So- now here's the funny story- or another lesson on how I should pay more attention to some things:

I load in the aluminum wire, get the welder set up and decide I should start on a slow speed and amperage. So, about 30 amps, housing all filed down, etc. etc. I make contact and I get poorly popping bacon sound and the welding wire is clumping and bouncing around the place.

So, crank up the wire speed and amperage- try again- still not the right sound and too much slag bouncing around.

Crank the amperage up- try again. Still not satisfied. Turn up amps. Crap! Got too close to the welding point and welded the aluminum wire to the inside (too hot for the aluminum apparently) of the copper tip. Replace tip and try again.

Ok- now the sound is right (can't see sh!t amidst the blue and green)- so I put it down and move it around for a few seconds- but am not seeing any buildup of slag/wire. Remove gun- look at housing- it's indented and no slag on top!

Where'd all that wire go?

Why- it melted the aluminum below outright and created a melted bubble on the inside of the housing- which, by the way, did seal the crack- but took up some space. Fortunately, the bubble is not blocking the water pathway significantly. Should have used a steel spacer or something inside the housing- damn!

Ah well, turned the welder down a bit, built up some material on the surface and filed it down- reassembled housing into pressure washer (turns out I really wasn't paying attention- the crack was on the pressurized output side- about 1200psi). Got tired and hot (it's like 95 degree outside) cleaned up and came in the house- will finish reassembly and testing later.

Lesson for Eric: Wake the f#ck up and pay attention!