Brazing aluminium.

[Vicval01]

Not sure if this post goes in Welding or General, but here goes.
I went to Gasweld, and told the gentleman that I had some 2 mm aluminium checker plate that I wanted to braze. Yes, I know tig welding is the preferred option, but my mig welder doesn't have a alum spool gun and I already had a bernzomatic flame torch.

I said I wanted low temperature brazing rods. He sold me some 4043 sticks, and I went home to have a go, having followed online tutorials. Sadly, the checker plate melted before I could get the rod to even soften. See pic of a test piece.

I went back to Gasweld, for some advice, where a different guy said he new nothing bout welding and couldn't help me. He told me the other guy was out briefly and I could wait for him. Which I did. When the second guy (Who had originally served me previously) arrived, he also had no idea how to assist, and asked me to wait a minute while he consulted his computer. I though he might have been looking for lower temperature rods, but after 5 minutes, I realised he was actually looking at a youtube videos on how to braze!
He showed me the video on how to braze, which of course was no help to me.
He suggested I go down the road and talk to the guy at an engineering firm for advice. Which I did.
The pleasant man told me they used mig for every type of aluminium welding and was unable to advise me on how to proceed.

So, fellow enthusiast, my question is, is there a lower temperature brazing rod that will allow me to braze the material? The project is a 1 metre long simple tool box that I would also rivet at the corner. Thanks.
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[ErrolFlynn]

This will be of no help as I've only brazed steel. A flux was involved and as I recall and the filler rod had to have a lower melting point than the job. If your job is melting before the filler I have to wonder whether you have the correct rod. I haven't done it for many years. I recall it was rather like soldering. I've also tried to weld aluminium. I could never do it. There was no indication of how hot it was and then suddenly it fell away from you.

Hopefully, someone else will be able to help.

[disco stu]

I picked up some of the cheap aluminium "soldering" rods/ coils on AliExpress and was amazed to find they actually worked, and quite well. Contains flux in it. Hard to get the part hot enough for it to work, but I've since had the idea of two torches-one as a general heat and the other to heat where I'm working and trying to join. Can be a little more precise with that heat working that way.

There's a tool shop out Bathurst that sells aluminium soldering rods, made by some bloke out near Braidwood or the back of Goulburn. It supposedly works well, has flux in it I think or is not needed. Will see if I can find his details, was responsive when I emailed with questions

[disco stu]

This is the website. Available in a fair few places from what I saw on a Google search

https://ultrabondweld.com/

Also, some videos on here that show it in use https://www.toolking.com.au/aluminiu...Idg9yHVvJnzZRs

[OxxAndBert]

Haven’t done it myself, but I know that the low temp brazing alloys are used a lot in aluminium air conditioning condensers and pipework on vehicles.

I’d personally try and avoid brazing completely and look at riveting and bonding (with the likes of Sikaflex) for the construction.

Steve

[Michael G]

One of the things that catches people out with Al welding is that the oxide melts at a higher temperature than the base metal. Not saying it was the problem or is the fix, but if the Al was not really clean, the oxide skin could have prevented the braze from flowing properly.

Michael

[BaronJ]

Hi Guys,

Welding any alloy is like soldering with lead ! Yes as Michael has said, the surface has to be clean and ideally pre-fluxed for a successful weld.

I've never found arc using a rod to be very good. Tig works well but only because you can control the heat source finely plus the shield gas helps to stop oxidisation. Using a copper backing plate helps particularly with thin plate.

In my earlier days I used a BOC Sapphire torch and cleaned the joint with a flux, but it is still very hard to see the transition stage just before the alloy collapses into a puddle.

[clear out]

My father used to oxy weld Al cast. I remember him modifying an inlet manifold to fit twin Carbys to his Vanguard. He later fitted a TR4 engine to his Vanguard ute.

He had blue tinted oxy goggles which I inherited and have now mislaid. Cobalt blue?
I did use them and with them you can see the Color change before the Al melts.

Mate oxy welded up a petrol tank for my enduro bike we built in the late 70s.

Ive since learned Tig at TAFE and definitely the way to go but you need to keep doing it or you fall off your bicycle.
H.

[Vicval01]

This is the website. Available in a fair few places from what I saw on a Google search

https://ultrabondweld.com/

Also, some videos on here that show it in use https://www.toolking.com.au/aluminiu...Idg9yHVvJnzZRs

Now that is an awesome bit of useful info. Thanks for that. I'll be investigating this product.

[Vicval01]

I picked up some of the cheap aluminium "soldering" rods/ coils on AliExpress and was amazed to find they actually worked, and quite well. Contains flux in it. Hard to get the part hot enough for it to work, but I've since had the idea of two torches-one as a general heat and the other to heat where I'm working and trying to join. Can be a little more precise with that heat working that way.

There's a tool shop out Bathurst that sells aluminium soldering rods, made by some bloke out near Braidwood or the back of Goulburn. It supposedly works well, has flux in it I think or is not needed. Will see if I can find his details, was responsive when I emailed with questions

Thanks, i look forward to hearing about that.

[Vicval01]

This is the website. Available in a fair few places from what I saw on a Google search

https://ultrabondweld.com/

Also, some videos on here that show it in use https://www.toolking.com.au/aluminiu...Idg9yHVvJnzZRs

Thanks. I rang Steve at Ultrabond. He was most pleasant helpful. I hope to get delivery soon.

[NCArcher]

I've used the low temp aluminium rods many times. They used to demo them at the wood shows by punching a hole in a coke can and then welding it up with a propane torch. I've got some around here somewhere. You have to clean the surfaces with acetone after brushing with a stainless steel brush. I think.....it's been a while since I used them. MAPP gas works well.

[ErrolFlynn]

I'd never heard of MAPP gas. Looked it up. It doesn't matter what you do, there's always a downside: Due to the high concentration of hydrogen in the flame the hydrogen infuses into the molten steel and renders the welds brittle.

I'd always thought of a flame as a heat source, never as an ingredient.

[OxxAndBert]

I'd never heard of MAPP gas. Looked it up. It doesn't matter what you do, there's always a downside: Due to the high concentration of hydrogen in the flame the hydrogen infuses into the molten steel and renders the welds brittle.

I'd always thought of a flame as a heat source, never as an ingredient.

Yes, but you don’t use MAPP gas for fusion welding steel.

Steve

[Jack Ryan]

I'd never heard of MAPP gas. Looked it up. It doesn't matter what you do, there's always a downside: Due to the high concentration of hydrogen in the flame the hydrogen infuses into the molten steel and renders the welds brittle.

I'd always thought of a flame as a heat source, never as an ingredient.

I don't think MAPP gas exists any more - it is mostly propane.

You won't be fusion welding much with it anyway, it's not hot enough. You can't oxy-propane weld steel anyway - possibly not aluminium either.

I don't braze aluminium but I would have thought it would be difficult with 4043 as the melting point is close to many of the common aluminium alloys. Even 4047 is quite high. The low temperature fillers like Ultrabond are the best bet. Something tells me that braze welding with TIG wouldn't work though.

Well, that's enough from someone who doesn't braze aluminium.

Jack