Aluminum solder

[Randy Ryan]

OK Guys, I'm stuck. Years ago there was a resin cored solder available for use on aluminum. I had some and it worked very well on clean joints, particularly well on K&S stock, whatever alloy that is. I bought some Solder-It several years ago at Toledo but have never been able to get decent results. In the demonstration the stuff flowed like water and sweated joints beautifully. So, barring this stuff, does anyone remember the solder I'm talking about and is it still available, OR, does anyone know of any aluminum solder that actually works?

[Bill Little]

Brother Randy,

Add me to the list of who needs to know! LOL!!

Bill

[Tim Wescott]

Harris Al-Solder 500 appears to work.  I got a kit at my local welding shop.

It comes with a special acid flux, which is nasty, and picky, too: the MSDS gives dire warnings about inhaling the stuff, what little got in really did irritate my nose, and the stuff absolutely couldn't stand being used with a torch: the flux activates at soldering temperature, and breaks down at not much higher.  So you have to use an iron.

But, for all that, it did stick music wire to aluminum.  I can't tell you how it works in the long term, because it was all for an idea that I didn't end up using in the air.

[Randy Cuberly]

McMaster-Carr lists several products under Aluminum Solder:

This is the most interesting I saw.

Solder for Aluminum

For soldering aluminum to itself and to its alloys. ROHS compliant.
98/2 Zinc/Aluminum—Solders aluminum with or without the use of flux. Melting temperature is 732° to 760° F.
60/40 Tin/Zinc—Recommended for use with flux, see Soldering Flux for Aluminum. Melting temperature is 390° to 635° F.

Approx.
Wt.

Each
98/2 Zinc/Aluminum
Approx. 38 Rods (0.125" Dia. × 18" Lg.)
2 lbs.
7664A4
$35.60

60/40 Tin/Zinc
Stick (0.280" Dia. × 13 1/2" Lg.)
3.4 oz.
7664A21
9.44

Rod (0.562" Dia. × 13 1/2" Lg.)
0.85 lb.
7664A11
36.33

Wire (0.125" Dia.)
1 lb.
7664A31
33.53

I haven't used this stuff myself but know that Raytheon uses it in a couple of critical applications on missiles...must work.  I don't know the process but would guess McMaster-Carr can provide.
They also list a special flux for this process and another flux that they claim can be used to solder aluminum with 60/40 tin lead solder...don't know about that.
Check it out!

Randy Cuberly

[Lauri Malila]

 Hi.

 The easiest & strongest I've found is made by Castolin Eutectic, it's their product #190. I learned of it from Robbie Metkemeijer, they use it for assembling pylon racing pipes (I guess the pipes are made of steel now, the aluminium ones tend to melt.).
 It works well at least with #6082 aluminium and other with less than 3% alloying.
 I use a simple butane flame, the important thing is to have a flame big enough, so that you can heat the whole workpiece near melting temperature of solder, which is really not far from melting temperature of workpiece.
 The flux is not inside the solder sticks, it comes separately as white powder that has to be mixed with distilled water.
 My opinion about the ones with flux inside the solder rod is that they are mostly crap. It can only mean that melting temperature is too low to achieve a good bond. They may work in some occasions, but I would'nt trust them with mufflers, exhaust headers and such.
 With normal brazing (like steel & brass with silver), the main purpose of flux is to protect the surfaces from oxydizing and to clean them. The temperature can be easily estimated from glow colour.
 Aluminium instead, it does not glow before melting and flux has also other purposes, to give indications of temperature.
 The manufacturer says that #190 can also be used with TIG but I have no experience of that.

 This brings a question:

 Does anybody know an easy way to regain at least a part of #6082´s original strenght after brazing? A heat treatment, I mean.

 Happy New Year

 Lauri

[Randy Ryan]

Thanks all for the help. I guess I should have clarified that this is not a structural application. I know about many forms of welding, brazing, soldering etc having been in it for many years.

Randy, I have used some of those products and they work well, however they do not "sweat", they tend to lie on the surface, they also discolor with time, at least the zinc based ones.

I have decided to machine my part from solid. I am making an exh stack for an old Ohlsson Gold Seal and since it will never be used, the piece could have been fabricated with low temperature solder. The original was a multi hit deep drawn stamping, I am not going to build progressive tooling for one piece. A billet part could be used and that's a plus tho not necessary. Finding an original part is highly unlikely due to the rarity of this engine.

[Bill Morell]

You might try asking Herb Walh, if he is still alive?, if he has any since he did a repo. of this engine about 35 yrs. ago.

[Lyle Spiegel]

I'm a metallurgist who spent nearly my whole career as a welding engineer. Retired as of Dec 2012. I have never encountered any reliable technique for making a solder joint where aluminum was involved. There various low melting point products which could be tried but I would not expect any structural strength or reliability. I would be very skeptical and careful. Might be better off using JB WELD. These comments are only with respect to soldering. I am not referring to aluminum brazing which is something very different
.

[George]

For brazing would you recommend AlumiWeld?

George

[Mike Callas]

Plate it copper then solder
Many a breadboard waveguides and filters have been made using this technique

[Randy Ryan]

Thanks all, I'm machining from solid, solves ALL my problems AND it will be a functional part.