Welding/Brazing Cast Aluminum

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Charley Davidson

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friend dropped off a piece of store bought art work that was broken at a welded joint. It is a cast aluminum and I have tried several solders with a propane torch with no luck, I even tried 2 different tig rods. Can I do it with the propane torch or do I need oxy/atc? What filler?

I can get aluminum stick welding rod but don't have a stick welder.

I think I have a spool of aluminum wire also but no spool gun or straight Argon. It's just 4 little tacks so I may be able to get enough wire to come out of my gun to do it. What ya think?
 
A picture of the item would help tremendously.

You have to grind/sand/wire brush the oxidation layer off of it, then clean the area with acetone. You'll never get it welded with that oxidation layer on it.

Depending on how big it is, you might have to preheat it to about 250*.

Harbor freight sells some aluminum brazing rods (alumiweld rods)that I've seen used for this type of thing. The working temp of these rods is only 750*, They are a zinc alloy.

A tig welder with aluminum rod might be the way to go.

The size of the piece will determine how you move forward. Aluminum acts as a heat sink, which is why you may need to preheat it.

Marcel
 
xalky said:
A picture of the item would help tremendously.

You have to grind/sand/wire brush the oxidation layer off of it, then clean the area with acetone. You'll never get it welded with that oxidation layer on it.

Depending on how big it is, you might have to preheat it to about 250*.

Harbor freight sells some aluminum brazing rods (alumiweld rods)that I've seen used for this type of thing. The working temp of these rods is only 750*, They are a zinc alloy.

A tig welder with aluminum rod might be the way to go.

The size of the piece will determine how you move forward. Aluminum acts as a heat sink, which is why you may need to preheat it.

Marcel
Click to expand...

I've used the alumiweld rods with a propane torch with pretty good results. I think that might be your best option Charley.
 
First thing first, Take the "Amazing fix all propane torch rod" and throw it in the river. It will be more useful there.

Oxy/acet never seams to work well on cast. I think its due to the dirty nature of the unmixed gasses and the crap in the aluminum. If you had a high quality pure casting it may do OK, but on normal castings it never turns out well. You need the AC current for cleaning action to make it work well.

Spool guns suck on aluminum in general, add cast aluminum into the factor and that equals fail. Spool guns on aluminum are only good for decoration and art type work mainly due to the DC current of a mig machine. Now if have a welder like a miller 350p with pulse waves, Then that's a different story.

To weld cast aluminum properly you need many things. You need a handful of different alloy fillers. A AC tig machine with adjustable HF and adjustable AC balance is a big help and you need an oven.

Sounds like all you really need is some JB weld and good prep work. Try drilling some holes in the broken ends to give more contact area for the epoxy to grab, and glue it together.
 
I have used both mig and tig successfully on aluminum cast repairs tig would be my first choice.

Jamie, there are decades of experience with mig welding aluminum for structural applications where tig welding is not cost effective and the distortion caused by excessive heat input to the base metal make tig inappropriate. Think most of the the Alaska inshore fishing fleet, these are boats built for severe service. It is about setup joint design and weld procedure.

As for ac cleaning cycle with tig it comes from the + side of the ac cycle, mig welding aluminum is done in positive stinger (reverse polarity) it is all cleaning cycle.

Bob
 
If you have a roll of al wire use the mig. Set up the weld so you can keep the cable and gun as straight as possible. Any kink in the cable will cause the wire to birds nest. You should be able to get the job done, but be aware, the wire will eventually birds nest. Don't use this all the time, but it will work for a small job.
Dave
 
As with every thing we all have are opinions that said. I've done all types Tig,Mig, and Oxy, Tig is by far the best for a clean nice looking weld. Mig sucks unless in a spool gun because no matter how hard you try you can't keep the line straight and then you better be fast you run with the weld. I have repaired castings with Oxy aluminum welding it takes some getting use to but works well if done as the instructions tell you. I welded the front house ping on a 1hp motor that was damaged in shipping and it still works great on my 7x10 bandsaw.

Todd
I'd have look but the Oxy rod was Aladdin they have different types.
http://www.aladdin3in1.com/products/3in1rod.php
 
Is this weld structural? A picture is worth 1000 words. If it is artwork, I would lean toward the JB Weld theory of repair.

Second option is TIG. Make sure to wire brush well with a stainless steel brush, and wash down with acetone. If it will fit (don't know what you're working on), you could even pre-bake it in an oven at 450 degrees just like outgassing prep for powder coating. Then brush and wash again. This will help to remove oil left over from the casting process from the pores in the aluminum. Cast aluminum welds dirty, but again if this is art and not structural, then it should be OK.

Best of luck,

GG
 
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