Low temp aluminium soldering?

[rcx132]

Hello everyone. I've had some joints to make in 0.8mm and 1.2mm sheet aluminium. I've tried common aluminium brazing rods, they work on thick 3mm aluminium, but not on thin sheet as the temperature just destroys the material.

I've found low temp aluminium solder, this stuff requires 220C: https://www.cupalloys.co.uk/store/1m-2207-Solder-Wire-1-5mm-dia-Flux-Cored-p276411610

But it requires special flux which is pretty pricey due to low availability (very few sellers, the only seller says they have to use special courier which impacts the price): https://www.cupalloys.co.uk/store/1m-2207-Solder-Wire-1-5mm-dia-Flux-Cored-p276411610

Just wondering if anyone knows of a lower cost flux? And also what your experiences are of low temp alu solder?

 

[JOEPRO]

Good timing. I just got this in the post today and I will test it today and report back on aluminium and also magnesium

 

[rcx132]

Good timing. I just got this in the post today and I will test it today and report back on aluminium and also magnesium

View attachment 444592

I bought those, and they worked very well on my test piece. I tried to pry the joint apart and the material failed before the joint!

But as I said, those rods are fairly high temp, I'm thinking of trying the low temp solder, which is apparently not as strong and requires expensive flux.

 

[rcx132]

Good timing. I just got this in the post today and I will test it today and report back on aluminium and also magnesium

View attachment 444592

Oh BTW the aluminium needs to be VERY clean. If it's used aluminium then a simple rub down isn't enough.

 

[Seadog]

This might work for you.

 

[masleeve]

I have used the Durafix rods with quite a good level of success , cleaning is key to a good result the stainless brush and the stainless spike need to be used .
My project was a selectionof brackets on a Leyland Atlantean that my friends were rebuilding .
The current one undergoing rebuild might be the justification to buy an AC/DC Tig .
Good luck

 

[JOEPRO]

Good timing. I just got this in the post today and I will test it today and report back on aluminium and also magnesium

View attachment 444592

Well maybe I didn't clean it enough- I used the supplied brush and also acetone. But this is about the best I could get on ali:



It did adhere but only to this peice hence it peeled off when I pulled it.

Magnesium- forget about it. The flux somehow weakness the magnesium and makes it crumble so a no go.

I'll stick to my TIG for Ali then! Worth a try though.

 

[JOEPRO]

Can you lap the joints and use a modern bodywork adhesive?

 

[Pigeon_Droppings2]

I used durafix to make a new lug on an alternator...they work very well....breaking thro the oxide layer is key.

The relevance is that durafix doesn't stick to steel so I made a steel former for my repair. Could you maybe use a sheet/block of steel behind the joint to spread the heat?

 

[bourbon]

I've been looking at the spec sheet for these. Looks to be mostly zinc based rod.so I would have thought a flux suitable for zinc would be ok?

 

[rcx132]

This might work for you.

Ah cool!

Well maybe I didn't clean it enough- I used the supplied brush and also acetone. But this is about the best I could get on ali:

View attachment 444596

It did adhere but only to this peice hence it peeled off when I pulled it.

Magnesium- forget about it. The flux somehow weakness the magnesium and makes it crumble so a no go.

I'll stick to my TIG for Ali then! Worth a try though.

That looks like a small piece, and you may have the issue I did, larger pieces spread the heat nicely, small pieces don't.

I would suggest the problem is with the user, not the product. Aluminium melts at around 660 Celsius; lumiweld only requires around 400 degrees - a 250 Celsius difference. I’ve used lumiweld on thin sections without any issue.

See this youtubevid as an example:

The issue I had is welding a panel, the heat would cause the metal to expand and as it shrunk it broke the weld. I went for rivots and PU sealer in that instance in the end. But still have odd small alu soldering jobs that need doing.

 

[CompoSimmonite]

I've successfully used the Durafix to repair aluminium castings (found pre heating in domestic oven helped ) however utter failure trying to fill holes in flat sheet without distortion. I'm sure there must be a method for thin / flat sheets but I gave up looking and simply made new alloy panels !

 

[Turbo]

I've successfully used the Durafix to repair aluminium castings (found pre heating in domestic oven helped ) however utter failure trying to fill holes in flat sheet without distortion. I'm sure there must be a method for thin / flat sheets but I gave up looking and simply made new alloy panels !

The normal demo for these is repairing a hole in a coke can so I guess its all down to practice!

 

[Matchless]

I have used Lumiweld and Technoweld to repair aluminium and Mazac castings, there is only around 10 degrees between Mazac and the Lumiweld rods and usually the mazac casting grows so if possible try to hold the broken casting in a former or mould made from say plaster etc, not much point in repairing say the top casting from a BMW E30 convertible roof gearbox only to find it is now 10% larger than the bottom casting! don't ask how I know! I also once used lumiweld to repair a casting flaw inside the inlet port on a BMW cylinder head, it was letting coolant into the inlet, impossible to mig or tig down an inlet port, biggest issue was getting the head hot enough, used a massive oven in a heat treatment business nearby, but it did work! Also repaired a corrosion hole through the back of a V8 Merc front cover, right behind the timing cover, it was spraying water onto the timing chain, did that repair without removing the timing cover..the owner had the head gaskets done twice before bringing it to me.......