Soldering Aluminium

[Radio Wrangler]

I used to have a little Valtock jeweller's meths blowlamp that was quite useful and served for soldering away from mains for me. Not sure where it is now.

David

[Anthony Thomas]

Originally Posted by David G4EBT

As I said earlier, I think the term 'welding' if often seen as a synonym for soldering or brazing, but it isn't.

You are correct David, it was soldering and not welding as I did write.

This repair material from Magna is usefull to replace brushes on some of those modern motors with aluminium field windings and all that is available of brushes are those with copper braids. They have to be attached somehow or the motor scrapped. In production they are "resistance" welded or almalgamated aluminium to copper.

Regardless, shame I did not keep the sample that I hard soldered together.

[Anthony Thomas]

Originally Posted by Radio Wrangler

they used to use a tallow candle as a flux.

The flux used in joining aluminium to copper and brass was the key component to the sucess of the "filler material" or solder if you will. The flux was a powder that had to be mixed with distilled water prior to use.

Originally Posted by Radio Wrangler

You could probably melt clean aluminium onto clean brass/copper with a shield gas and flux, and get a bond, but it would be a solder type joint.

The flux mentioned above was quite gassy and agressive, it had to be cleaned off afterwards. The other two "repair alloys" previously mentioned (Magna 53 & 55) that were used with oxyacetelyn each had their own flux probably due to them being used for either magnesium based alloys or zinc alloys. Use the incorrect flux and they just didn't work at all.

Tony

[Andrew2]

Originally Posted by merlinmaxwell

Another aluminium soldering tip is if you use aluminium foil for a screen one way of getting a good connexion is to form a blob of ordinary solder on it and then rub the tip of a soldering iron through the solder. This removes some of the oxide and makes a fairly good joint.

I've used this technique with success. I first saw aluminium soldered using ordinary 60/40 solder back in the early 70's. A good hot iron and plenty of wire-brushing eventually got a good joint.
I've also used the 'rubbing' method on stainless steel (or it may have been 'staybright' or similar) I wanted to join a length of wire to a s/s whip antenna, but couldn't be bothered finding some acidic flux or whatever is required. So I used an ordinary 25 watt iron, ordinary flux and plenty of rubbing. After quite a while a tiny pinprick of solder bonded, and after that I managed to make it cover a larger area and successfully soldered the wire in place.

[wireful3]

This has reminded me of an advert I saw in an old technical magazine, probably from the 1950s or 60s. It was a soldering iron I think by Solon specifically for soldering aluminium. It looked like a normal soldering iron with a piezo electric unit that produced a sonic vibration at the tip. This was claimed to clear away the oxide on the metal. I have seen no references to it since so suspect it was not very successful.