Aluminium Solder

[Roger B]

A few years ago I bought some aluminium solder from the DIY supermarket as a 'come in handy'. I hadn't really found a use for it up to now. The radiator support for my two cylinder engine seemed to be a good place to try it. I needed to join a 25mm square 10mm thick piece to the end of some 30x2mm angle. A couple of M3 screws would have sufficed.
I set the pieces up on my fire bricks and attacked with my camping gaz blowlamp. Not a lot happened for a while but I kept cautiously poking with the solder stick. Quite suddenly it melted and flowed.
The results look good, I overheated it a little and did not get full penetration but it didn't break when I drilled a 5.5mm hole in the end.
Maybe beginers luck but I am impressed so far 

[Admiral_dk]

Thanks for showing Roger 

I have seen a few demonstrations on shows over the years, of similar products - but I have no info from any off those - so just seeing the picture, helped me getting a name = Rolot 604.

Per

[Jo]

I have some of this stuff. My Supplier tells me that while it starts out the right colour after a year or so it gets darker  No problem if you are painting it 

Jo

[Admiral_dk]

Nice to know too Jo 

I must admit that I always thought of it as a repair tool.

[crueby]

Did you need to use a flux with it, like with silver solder?

[Vixen]

I have used something similar?? stuff called Techno-weld. It is an alloy of bismuth + tin + antimony which needs no flux, but you do need to remove the oxide coating off the aluminium with the supplied stainless steel wire brush and then use the stainless steel rod to scratch the aluminium's surface, just before you add the weld rod. The weld rods melts between 380 and 408*C and dissolves into the aluminium being welded. The guy demonstrating the Techno-weld rods makes it look very easy, it probably is, when you have used it as often as he has. It does take practice to get a decent looking weld. A good welded joint seems to be quite strong.

Mike

[steamer]

I have used something similar?? stuff called Techno-weld. It is an alloy of bismuth + tin + antimony which needs no flux, but you do need to remove the oxide coating off the aluminium with the supplied stainless steel wire brush and then use the stainless steel rod to scratch the aluminium's surface, just before you add the weld rod. The weld rods melts between 380 and 408*C and dissolves into the aluminium being welded. The guy demonstrating the Techno-weld rods makes it look very easy, it probably is, when you have used it as often as he has. It does take practice to get a decent looking weld. A good welded joint seems to be quite strong.

Mike

I have seen the same demo Mike.    Some thoughts......Most aluminum alloy sections that we use are most often the common wrought alloys...  6061-T6, 6063-T6, 2024-T4, 7075-T6...ect   maybe some A356 cast parts...
Now most of these wrought materials are Precipitation Hardened....which is the "T" number at the end of the designation....here's the rub....once you heat a piece of Aluminum that's been heat treated like this to say anything over 350F...the heat treat is gone.   the material strength properties will have dropped pretty significantly.    Now....for 99% of what we would use this for...that's probably just fine...but do keep in mind not to be soldering up your latest gantry crane from this stuff    hmmmmm?    If it matters....get a proper TIG welder on the job.

I watched this youtube vid on a shop test of this material....pretty interesting.....at least from the pragmatic side of things...
I don't think it's any worse than say   JB weld....

<a href="https://www.youtube.com/watch?v=k21JDVdGalY" target="_blank">http://www.youtube.com/watch?v=k21JDVdGalY</a>

Dave

[crueby]

...once you heat a piece of Aluminum that's been heat treated like this to say anything over 350F...the heat treat is gone.   the material strength properties will have dropped pretty significantly.    Now....for 99% of what we would use this for...that's probably just fine...but do keep in mind not to be soldering up your latest gantry crane from this stuff    hmmmmm?    If it matters....get a proper TIG welder on the job.

...

Dave

If it was TIG welded, wouldn't that also heat up the metal? Localized for a large part, but what about for a small one, model-sized bits? Thanks for the tips and info!

[steamer]

Yes....you're right about heat affected zone....no I can't predict the outcome with the filler metal an all....though usually the welded joint is much stronger than the surrounding metal....and it makes me ask why?

I'm sure there are some TIG welders here who can jump in on this one

Dave

[Jasonb]

For things that matter the welded structure is retreated as a whole, things like ali bike frames certainly are.

[Roger B]

Chris, these rods are coated in a white flux. The flux started to melt and flow almost at the same time as the metal.

[steamer]

For things that matter the welded structure is retreated as a whole, things like ali bike frames certainly are.

Thanks Jason...that makes sense....I haven't done any welded structural aluminum.  When it's mattered the projects I worked on were all riveted panels...but yes.....reheat treating the object makes sense.

Dave

[fumopuc]

Hi Roger, here a very special source for Aluminium and other soldering in Europe.
https://rexin-loettechnik.de/
An excelent service by phone is always available. Currently the owner has some trouble with his e-mail acount.

[Don1966]

I have used these rods and they do work to a certain extent. I find it make a porous weld. The material has to be well clean with a stainless brush fo it it adhere to the material your welding. Melting temp is way lower then the aluminum! Just my two cents....


Don

[Muzzer]

...once you heat a piece of Aluminum that's been heat treated like this to say anything over 350F...the heat treat is gone.   the material strength properties will have dropped pretty significantly.    Now....for 99% of what we would use this for...that's probably just fine...but do keep in mind not to be soldering up your latest gantry crane from this stuff    hmmmmm?    If it matters....get a proper TIG welder on the job.
...
Dave

Interesting - I hadn't twigged that many of these alloys are PH. Although not the definitive font of all knowledge, Wikipedia says of 6061T6:

"6061 is highly weldable, for example using tungsten inert gas welding (TIG) or metal inert gas welding (MIG). Typically, after welding, the properties near the weld are those of 6061-T4, a loss of strength of around 40%. The material can be re-heat-treated to restore near -T6 temper for the whole piece. After welding, the material can naturally age and restore some of its strength as well. Most strength is recovered in the first few days to a few weeks. Nevertheless, the Aluminum Design Manual (Aluminum Association) recommends the design strength of the material adjacent to the weld to be taken as 165 MPa/24000 PSI without proper heat treatment after the welding."

Thanks for the eye opener!