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Old 12-19-2014, 02:42 PM   #1
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Default Welding to cast aluminum

Hey guys, I'm clocking my turbo and welding a bit of round to the compressor housing to move it correctly. I was wondering if any of the more experienced welders could point out any tricks or "gotchas" of welding to cast aluminum.

Filler type, size, power, etc.

Using a TIG.
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Old 12-19-2014, 03:00 PM   #2
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Everyone says to pre-heat when welding cast, but I didn't find it necessary. Although, the compressor outlet isn't stressed much, so my main focus was on air sealing, than full penetration and such. I'm not sure on the filler type that I used, it's whatever we use for all aluminum welding in the shop, but I do know it's like 1/8". I don't remember the power, but a general rule is twice the amperage per thousandth of inch of thickness. I'm guessing I just maxed out our Miller at 200 amps and modulated. Clean, clean, clean! Aluminum needs to be super clean, including wire wheeling very thoroughly, and acetoning the part, tungsten, and filler. I used 3/32" red thoriated tungsten.

FYI, I'm certainly not a professional (especially with aluminum), but I've been around welding some time and this certainly worked well for me.

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Old 12-19-2014, 03:51 PM   #3
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In my experience it's a bit of a crap shoot with parts that you don't have an extra of to do a test with first. Cast AL has such a wide spread of different possible properties that you're usually guaranteed that you'll need to start with a best guess on settings and spend the first 1" of welding making adjustments.
Beware the low-quality cast stuff. I ran into some once that literally deteriorated away from the heat and exposed a porous core that looked like the inside of a bone. It was a trip. And tons of fun to get it sealed back up.

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Old 12-19-2014, 11:13 PM   #4
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An aluminum casting has a distinct possibility of molding sand buried in the casting. I'd suggest this is a problem about once in 20 pieces. If found, it can be ground out, or floated to the surface by continuously circling the spot with the torch until it floats to the surface. Then grind it out.

Pre-heating largely depends on the type of machine. The "synchro-wave" type machine where the neutral axis of the AC can be moved around will preheat so rapidly that about 5 seconds of patience are all required. The non-synchro will need about 20/30 seconds to be ready to weld.

There are other factors that make the synchro a superior aluminum welder, but the old style machines can still do a very good job.

Cast Al needs to be cleaned a bit better than wrought. The same weld rods as used for wrought work as good as any other. Heat requirements still depend solely on the material thickness.

In the photo you present, the black specs are sand grains from the cast process. The silicone stuff turns black when roasted. With the welds as you show them, the black specs can be ground off and a nice bead laid over the top. The black stuff won't make it through the second weld.

Compressor castings are virtually always a quality casting, regardless of where they came from. The Chinese casting are just as clean as Garrett's.

a scotch brite buffer will remove some of the black, and all of the ugly white oxidation stuff that looks like frost.

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Old 12-20-2014, 01:21 AM   #5
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Tig ended up not working. Kept burning away, and couldn't get a solid pool. So we switched to stick welding. Worked great.
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