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Brazing aluminum with flux-core rods

 
pollinator
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When I weld steel at home, I use my MIG welder… my neighbor has an arc welder & rods, if I need to use that setup for steel. But neither he nor I have a spool gun for aluminum-welding wire. So, I haven’t been welding alum.

Anybody here done aluminum brazing using flux-core rods? Have you found the low-melting-temp rods to work well for you, or not? (good adhesion, strength, etc?)

As an example of what is readily available in my regional marketplace, here’s this page advertising Hobart rods.  Hobart is a good, standby welding equipment/supplies brand — but I’m not stuck on any particular brand. It seems many brands have been advertised in recent years.
https://www.princessauto.com/en/detail/8-pc-1-8-in-aluminum-brazing-rods/A-p8676884e

Mainly I’m just interested to hear whatever sort of experience you’ve had with flux-core for aluminum.  And P.S. to stewards, moderators, techies: if you feel this post should go in another Permies forum (like Repair), please cross-post it there… but I believe welding & brazing are homesteading skills, so please leave it here too, okay?

Thanks.
 
pollinator
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I am certified to weld Aluminum, but I never really like it. It is hard because the melting point of aluminum is kind of low so by the time you get the arc established, the weld can sag out on you, especially overhead welding.

They key point about welding aluminum is that it requires AC welding, not DC and depending on the method, having better control of your arc. With tig welding, you want a foot pedal so you can control your heat instantaneously, and with wire feed, you want to dial in you arc so instead of it being like a rolling wave, you get the peaks of your arc to start faster, end faster and shorten your frequency so that you are taking a lot of the heat out of your weld. But it depends on what you have for a welder, and what method you are using too.

With wire feed, the wire is so soft that you have to keep your spool gun almost straight out of the feeder otherwise it will not pull the soft wire around bends of the lead.

Tig welding aluminum is actually pretty easy, but wire feeding aluminum is probably some of the hardest welding I have done, right up there with welding cast iron.

(By the way, I do not braze, so when you said "braze" from your description I took it to mean tungsten inert gas welding (tig), or heliarc welding. A lot of welding types have the same name).
 
pollinator
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Well, you learn something new every day. You can gas braze aluminum.

 
Joel Bercardin
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Caleb Mayfield wrote:Well, you learn something new every day. You can gas braze aluminum.


Yeah, that's the approach I was wondering about, for a couple reasons. One is, to wire-feed it people generally use a spool gun, because aluminum wire is soft and, unlike steel wire, tends to foul up when it's run through an ordinary conduit & MIG gun (or "torch end"). Another is, I'd be joining aluminum components infrequently enough that I don't want to invest in a spool gun.

I've heard of guys using a propane torch, also of guys using oxy-acetylene (and I'm supposing with a wide, soft flame). But that's where I want to get the advice about best approach, and how it works out.
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