Silver Soldering

[John Richards]

I wish to Silver Solder Brass and Bronze to Mild Steel, I have a Tub of G.P. Flux,
I`m assuming this means "General Purpose" and that seems quite adequate to
Silver Solder Brass to Bronze,
My Question is:
Will the G.P. Flux be O.K. or will I need some thing else??!.

Regards,

[DJ’s Timber]

As long as it is the creamy smooth liquid paste type which is white you should be right. Make sure every thing is absolutely clean and try not to handle the areas that you are joining.

[DanP]

Give it a go and see what happens.

[John Richards]

Thank you both for your imput, It is that White Creamy Paste as stated,

Regards,

[HavinaGo]

It might be stating the obvious but take care with the type of silver brazing rod you use .. the old blue tip (CIG 245) was good on ferous metals.
The plumbing phos copper rods are no good.

[Grahame Collins]

Hi John,
If I can teach High school boys to silver solder ,I can show anyone.
It is an easy to follow a procedure.
I'll assume you have an oxy acetylene plant .If so set it up on 2 to 3 psi regulator pressure. Use a nuetral flame on minimum setting. As a guide you should be able to wobble the flame.That setting is very important. Low pressure,low volume is the go. Flame settings that are too high will cuase the solder to prematurely oxidise.

Also is the cleanliness - sanded up to shiny clean. your flux if dried out can be brought back by adding water until it regains a cream like consistency. Place the flux only where you want the solder to run.

Heat the larger of the two components to begin with as it will take longer to heat and gradually allow heat to transfer to the lighter part.This is important as both parts need to be the same temperature if the solder is to flow and run correctly.
Do not introduce the solder until the temperature is suitable. An indicator of that is from the flux colours.It will go from a dried toothpaste appearance on initial heating to a clear water like appearance until just before before the correct fusion temperature. A quick rub of the filler wire against the desired fill area will be rewarded by the wire taking immediately between the fusion faces.

Remember that the parent material temperature is what fuses the filler rod.It should not be melted with the flame.

The solder deposit should finally appear a shiny golden colour.If it looks dull or grainy , it has been overheated .

a bit of practice won't hurt

Grahame

[journeyman Mick]

Grahame,
just wondering if you can give us a rundown on the makeup of the different colour coded silver solder sticks and usage of same. Don't know if you want to start a new thread, "silver solder how to", you could copy and paste all your above post. Thanks for all your informative posts,

Mick

[John Richards]

Grahame,
I too second Journeymans request, This can be a small part of running & owning
a Lathe but none the less a very much needed part at times.
Thank you for your advise, I will adhere to it, By the way, I`m using a Single Burner
with Propane Gas on this Silver Soldering Job, Is there anything different in and
around the preparation??

Regards.

[Grahame Collins]

Hi John,
no probs with Lp .I have not done a lot with that particular process, but the little I have ,suggests that LP is way more difficult in heating up the work.That is because of its low calorific value.
In some respects it may well be easier from a novice point of view in that the temperature rise would be gradual and the fusion point would not come and go rapidly as is the case with Oxy. (read the other threads on that )

Preparation remains the same - clean! clean! clean !

hope this helps
Grahame

[neksmerj]

Hi Grahame,

Recently I tried to build up a worn cast iron part with brass shim using a general purpose flux paste and a butane torch. No success what so ever. The area to be built up was very small, 6mm x 1mm. The build up was approx 0.1mm.

Separately, I could heat the part to cherry red, and separately I could melt the brass shim, but put the two together, no luck. The tiny piece of brass shim, simply melted into a ball, and just sat there. I tried using brass because it's all I had and the Gas & Gear shops were closed over the Christmas break. Was I trying the impossible, if yes, which brazing or bronzing stick should I get? Your comments would be appreciated.

Regards,

Ken

[Grahame Collins]

neksmerj,

What can be used are manganese bronze or nickel bronze brazing rods( completely different from silver brazing )with appropriate flux.
The general silver brazing flux if that's what you where using is unsuitable.

Beware if the cast iron part is unevenly shaped as less than uniform heating and cooling sets it up for a fracture.Its best left to someone with experience.

Grahame

[Darren Khnobbs]

Hi John,
no probs with Lp .I have not done a lot with that particular process, but the little I have ,suggests that LP is way more difficult in heating up the work.That is because of its low calorific value.
In some respects it may well be easier from a novice point of view in that the temperature rise would be gradual and the fusion point would not come and go rapidly as is the case with Oxy. (read the other threads on that )

Preparation remains the same - clean! clean! clean !

hope this helps
Grahame

Dear Graham, no offence mate, while you claim to be a "welding pro" and seem to be surrounded by thousands of adoring fans, that lap up your every word;

The fact is that as a genuine welding professional myself, I find that a great deal of the information that you are passing off as "expert testimony" is either hearsay or clearly not connected with "the facts"...

What you say here is just untrue - and you contradict yourself as well.

"Hi John,
no probs with Lp .I have not done a lot with that particular process, but the little I have ,suggests that LP is way more difficult in heating up the work.That is because of its low calorific value."

LPG Australia:

Liquefied Petroleum Gas (LPG) is the generic name for mixtures of hydrocarbons (mainly propane and butane). When these mixtures are lightly compressed (approx. 800 kPa or 120 psi), they change from a gaseous state to a liquid. LPG is colourless, odourless and heavier than air. A sulphur based chemical (ethyl mercaptan) is added to give it a smell like rotten cabbage, so that even a very small leak can be easily detected.

LPG burns readily in air and has an energy content similar to petrol, which makes it an excellent fuel for heating, cooking and for automotive use.


Ok so without nit picking we will split the calorific values of propane and butane - and compare them to acetylene.

Propane:

Acetylene 56,000 kJ/m3

Butane C4H10 133,000 kJ/m3

Propane C3H8 101,000 kJ/m3

So your way wrong on the energy values...............

Combustion Temperature:

Fuel Gas Oxygen (oC) Air (oC) Acetylene 3,100 2,400Propane 2,820 1,980
Butane is around the same as propane in both air and with oxygen.

The only REAL difference between LPG and Acetylene flames is that a purely neutral Acetylene / Oxygen flame, really is a neutral "welding" flame, in a concentrated small set of cones, and a LPG flame is by necessicity - spread over a much wider area and through a much shorter volume

As far as silver soldering with LPG or LPG oxygen goes, it's just fine.

What Acetylene makes up for in it's concentrated point of heat, that dissipates quickly as the heat flows away from the point, the LPG makes up for in dispersing the greater volume of heat over a larger area.... so that the hot to cold transition is much more limited, and the welding area, stays hotter, rather than bleeding off.

"I have not done a lot with that particular process, but the little I have ,suggests that LP is way more difficult in heating up the work."

So my next question is how can you be passing a "suggestion" off as an expert opinion?

LPG / air is an excellent way to heat small or large areas quickly and cheaply, with very portable "single gas" equipment.

Most silver soldering is at or below red heat.... so what are you doing saying it's no good?

Much of your "expert opinion" is factually wrong, misleading and based upon what you have said, "your limited or lack of experience".

So why are you trying to pass yourself off as an "welding expert", while posting information that is both untrue, and incorrect.

I am not trying to be disrespectful, but what your saying is leading people to make wrong decisions - in purchases, or unknowingly result in faulty work - and your actions may even end up getting some one seriously injured or killed.

To me you do not sound like a pro - or an expert.

[MrB]

Hi John, how did you go with your silver soldering job?
I will echo the post above regarding silver soldering with a Propane or Butane self blowing torch(like the Bernzomatic style), it's done regularly by Model Engineers building copper boilers for locomotives.
A refractory firebrick hutch will be a great help in containing the heat in your work.
At a pinch you can use normal house bricks(as I do) but make sure if you drag some from the yard they are bone dry as any moisture will flash off into steam and may potentialy cause bricks to explode.
Also, it's best to use the correct flux for your silver solder, particularly with the high silver bearing Eazyflo style solders.

I'm no expert(but I have used a self blowing butane torch with success) so will recommend a great book that is available that discusses all these things in great detail using hobbyist equipment(written for Model Engineers):
Soldering and Brazing by Tubal Cain
Workshop Practice Series #9
ISBN: 0852428456
DD: 671.56 CAI

A book store like Boffins is likely to stock it for about $20, ordering it thru Dymocks or Angus and Robertson will involve a 3 month wait(Don't ask how I know!)
Or, you could borrow it via an inter-library loan, four libraries in the metro area have it(along with many other books in the workshop Practice Series), Mirrabooka, Cottesloe, Warnbro and Murdoch public(Rockingham).

A google search for it will get you many reviews, heres an Amazon.com page for the book.

[watson]

RULES OF ENGAGEMENT
G'day all,
I would wish that I knew enough about welding to disagree with this forum's Moderator.
I don't, so I don't.

I would like to point out though, that disagreement with a post, or advice does not give anyone the right to denigrate another member.

The correct way to disagree with a post, is to say..."I disagree...for the following reasons"......and then leave it at that. This opens debate....not argument.

There is no reason to then continue denigrating the advice giver, or question his/her qualifications,for whatever reason.

Now I feel like somebody's Mum.

But feel free to disagree..debate points to death....but leave it at that level.

Noel Watson
Administrator

[Ashore]

I on the other hand have done a lot of silver soldering in the field if you will and have found that rather than " What Acetylene makes up for in it's concentrated point of heat, that dissipates quickly as the heat flows away from the point, the LPG makes up for in dispersing the greater volume of heat over a larger area.... so that the hot to cold transition is much more limited, and the welding area, stays hotter, rather than bleeding off." with acetylene I can apply heat directly to the area I want to silver solder rather than heat a larger area and then I don't effect another joint nearby that has already been done, so for most of the silver solder jobs I have done in over 30 years LPG would not have been the best method or even a practical method to use and to say "As far as silver soldering with LPG or LPG oxygen goes, it's just fine." it is not it depends on the job where it is :cool:
And mate I aint no adoring fan of anyone

[Claw Hama]

Hi Guys having silver soldered and brazed thousands of jonints from 1/8" Copper to 3" steel for 25 years as a refigeration and air conditioning technician on large multi storey plants and oil rigs I have found both Oxy and LPG to be fine for silver soldering. You generally need a soft general area flame unless as Graham says you don't want to melt the next joint and then you wrap it with wet rag and keep it wet. Darren is also very correct with his heat content etc. Regardless of the type of flame the silver solder filler rod is melted by the primary metals you are joining with maybe the aid of a small whisk of the flame accross the rod and metals as you are about to join the metals, as it all starts to flow pull back you flame so you have a minimum amount of heat on the joint. The silver solder should go up into the joint by capilary action if your joint is clean and have had that general heat on the whole joint. I have always found putting a small dot of ss near the joint while heating, when this dot is melted by the heat of the "metal" the joint is ready to solder. The brass and bronze will usually get hotter more quickly than the steel but the steel will burn quicker if you put too much heat on it. Gently is probably the key word and use the dot, it becomes very obvious when the joint is ready to solder. I also would not use too much of a hutch as you can get a lot of uneven heat blowback if you don't make it correctly and it probably isn't realy required if your flame is big enough.
Old school brown tip (15% from memory) was fine for copper to copper, copper to brass but blue tip (25A% I think ) was better for copper, brass to steel. As everyone has said make sure everything is clean and oil free. Its not realy that hard or technical just takes a little practice. The higher the silver content the finner your joint. Good luck.