Silver Soldering Inverness or Elgin way

[Carl Wilson 4Participant @carlwilson4]

I’ve been reading the silver Soldering article in MEW and enjoying it as well as learning. I think it would be a good process for me to learn as it could solve a few problems for me. I’m generally tig welding most things.

Wondered if there is anyone in the Inverness or Elgin area with the kit that would be kind enough to consider letting me have a go, and show me the ropes. That would be an easier way to get a good handle on how the process could work out for me and what gear I would need. I’m a monkey see monkey do type.

Thank in advance

Carl.

[Carl Wilson 4Participant @carlwilson4]

[Speedy Builder5Participant @speedybuilder5]

Hi Carl, can you soft solder plumbing fittings? If you can, then silver solder follows much the same. Surfaces should be clean, flame should be hot enough to get the part(s) to dull red heat. Just to try it out, buy a length of silver solder and packet of flux. for examples look here **LINK**
Buy a small gas blow lamp from B&Q, SCREWFIX, whoever you like – nothing too expensive, borrow your neighbour's perhaps. Now experiment with small parts, Silver solder a 1/4" copper tube into a bit of brass plate with a 1/4" hole drilled into it. You will see just how easy it is.
If you want to make a boiler, that is a very different kettle of fish. Experiment and learn from your mistakes. Not too much heat, but just enough. Every job is different. Get a bit of fire brick or thermalite block. See how you can conserve heat by using these.
If there is someone nearby all the good, but I would just do it.
BobH (Ex Turriff)

[Carl Wilson 4Participant @carlwilson4]

Fair comment and thanks for the advice. What I was thinking was that in learning any new technique there are all the little tricks and bits of know how that you learn over time. Usually a long time. So I was hoping to have someone show me and thereby speed up the whole thing.

[Neil WyattModerator @neilwyatt]

I was wondering what the difference is between the 'Inverness' and 'Elgin' techniques?

Is this like the 'West Lothian' question?

Neil

[Keith HaleParticipant @keithhale68713]

Hi Carl

Two thoughts.

Firstly

get to understand the principle of silver soldering – capilllary flow.What to do, why and how. Visit **LINK**

There is a short video clip to help you.

Secondly

there is a separate video going into more detail about the principles and how it relates to boiler manufacture. The best of both worlds. Good technical advice and a demo from a true professional Helen Stait of Western Steam.

But for help at any time call us on 01909 547248

Regards

Keith.

[Carl Wilson 4Participant @carlwilson4]

Thank you for that interesting info. The thing I want to solder is not unlike a boiler in principle. Except that it is made up of a series of aluminium tubes. It can be thought of as a type of heat exchanger.

I was and may still tig weld this assembly. The two issues with this are as follows:-

Aluminium is weakened in the Haz after welding, though I have processes to deal with this.

Some of the tubes are quite small and so the welding is going to be “interesting”.

So you can see why silver Soldering looks attractive. There are other issues that may rule it out like mechanical strength at elevated temperatures, but this is a preliminary investigation.

[roy entwistleParticipant @royentwistle24699]

I think I am right in saying that you cannot silver solder aluminium

I believe it can be soft soldered using special fluxes and alloys

Roy

Edited By roy entwistle on 29/05/2017 10:42:45

[Carl Wilson 4Participant @carlwilson4]

Thanks Roy – would that be due to the process temperature required or some other reason? Just reading that brazing is up at 610 degree C, similar or at aluminium melting point.

Edited By Carl Wilson 4 on 29/05/2017 10:58:31

[Neil WyattModerator @neilwyatt]

Posted by Carl Wilson 4 on 29/05/2017 10:56:57:
Thanks Roy – would that be due to the process temperature required or some other reason? Just reading that brazing is up at 610 degree C, similar or at aluminium melting point.

Yep, silver soldering becomes 'alloying' when attempted with aluminium

Neil

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by Carl Wilson 4 on 29/05/2017 10:30:48:
Thank you for that interesting info. The thing I want to solder is not unlike a boiler in principle. Except that it is made up of a series of aluminium tubes. It can be thought of as a type of heat exchanger.

I was and may still tig weld this assembly. The two issues with this are as follows:-

Aluminium is weakened in the Haz after welding, though I have processes to deal with this.

Some of the tubes are quite small and so the welding is going to be "interesting".

So you can see why silver Soldering looks attractive. There are other issues that may rule it out like mechanical strength at elevated temperatures, but this is a preliminary investigation.

In that case HTS2000 may be the stuff to use. I'very been impressed with it.

HTH,

Rod

Edited By Roderick Jenkins on 29/05/2017 11:45:31

[Carl Wilson 4Participant @carlwilson4]

Interesting stuff this HTS2000. Seen similar before. Only niggle is can never seem to find any definitive mechanical and physical properties for it, or a composition. What I am building is also a pressure vessel so I need to know the properties for certain.

[Carl Wilson 4Participant @carlwilson4]

Well the website reckons a uts of 45900psi, which is 316MPa. This is about the same as 6082. Reckon I might have to get some and do some joints then pull them apart….

[Dod MoleParticipant @georgeclarihew]

Posted by Neil Wyatt on 28/05/2017 19:27:43:

I was wondering what the difference is between the 'Inverness' and 'Elgin' techniques?

Is this like the 'West Lothian' question?

Neil

Nivvir min, Inverness technique is in the Gaelic and Elgin technique is in Doric spik.

Edited By George Clarihew on 29/05/2017 20:37:12

[Keith HaleParticipant @keithhale68713]

Posted by Neil Wyatt on 29/05/2017 11:06:11:.

Yep, silver soldering becomes 'alloying' when attempted with aluminium

??????????????

Keith

[Carl Wilson 4Participant @carlwilson4]

The row of question marks suggests you don’t agree with Neil’s assertion, Keith. What is your take? Does the oxide layer on aluminium have any effect?

While we are about it, I have had a little bit of exposure to Tig brazing, using either bronze or aluminium bronze rods. I concluded that I needed more practice.

I think that with a gas torch ie mapp or the like it would be a struggle to get an aluminium assembly up to temperature. It conducts heat away so well. I know from my tig welding the amount of energy in the form of current that is required to melt it.

Edited By Carl Wilson 4 on 30/05/2017 09:19:23

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 29/05/2017 11:06:11:

Yep, silver soldering becomes 'alloying' when attempted with aluminium

Neil

I think Neil was suggesting that it will all melt into a messy lump hence the winky

To silver solder you need to get the actual parts upto a temp of at least the melting point of the solder so that would mean getting the ali upto 650+deg, it may not flow but would start to sag and distort.

Edited By JasonB on 30/05/2017 10:06:18

[Carl Wilson 4Participant @carlwilson4]

Bit if a non starter in that case.

[roy entwistleParticipant @royentwistle24699]

Perhaps Keith from Cup Alloys would explain why aluminium can't be silver soldered ( Or if it can, how )

Roy

[Carl Wilson 4Participant @carlwilson4]

I’m sure he can. My feeling is the the very high thermal conductivity would make things difficult to get the workpiece up to temperature.

[Mike PooleParticipant @mikepoole82104]

Would the melting point of aluminium and silver solder being similar be a problem ?

Mike

[JasonBModerator @jasonb]

That is what I said above. Soft soldering stops at 610degc and brazing including silver soldering starts at 610deg which is basically when aluminium will melt.

Also the fluxes used will not remove the oxide from any metal containing more than 2% aluminium (eg Aluminium bronze) so won't wet the surface of the various aluminiums

 

Its all on the Cup site if you care to read it.

Edited By JasonB on 30/05/2017 16:27:33

[Michael GilliganParticipant @michaelgilligan61133]

If I may intrude for a moment:

On this previous thread **LINK** I shared some details of Thesscal "A"

http://www.model-engineer.co.uk/forums/postings.asp?th=118175

These may be of interest to those wanting to solder Aluminium.

MichaelG.

[Carl Wilson 4Participant @carlwilson4]

Fluxes may not remove oxides from the surface of aluminium but anions enveloped in an argon shield most definitely will.

Thanks to all for the input. Plan A stands and it will be TIG welding.

[Keith HaleParticipant @keithhale68713]

And finally,

Melting point of pure (99.99%) aluminium is660 deg C. Melting point of commercially pure (99.5%) i 635 deg C. Alloyed this can reduce further to 500 deg. Lowest melting point silver solder was 620 deg C (Now banned fpr sale) Currently the lowest is 652 deg C (56% silver).

How good is your heating technique ?

Any soft solder can be used to solder aluminium. You only need the right flux. It is expensive to deliver. Visit the CuP Alloys Roadshow or get it at an exhibition. The savings will easily cover your entrance fee. http://cupalloys.co.uk/soft-solder-fluxes/

If the aluminium content of your bronze is higher than 2% but lower than 10% tweek your flux. Add 25% by weight of kitchen salt to your standard flux. When mixed with water into your paste, the extra chloride ions will remove the aluminium oxide, Alternatively buy a speciality flux and that is an expensive way to buy salt.

The search is on for a filler metal that melts about 450 deg C. Probably based on tin, copper zinc antimony alloy or whatever it will be an overnight winner guaranteeing the patent holder a fortune. As long of course that it is not as brittle as carrot!!

By the way, note that the link to the silver solder is for rods that are only 250 mm long!

The industry norm is 500mm so it is not a true comparison.

Regards

Keith

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Edited By CuP Alloys 1 on 31/05/2017 09:51:50

Edited By CuP Alloys 1 on 31/05/2017 09:52:26

Edited By CuP Alloys 1 on 31/05/2017 10:10:05

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