Silver braze/solder

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TimTaylor

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I see your point Tim, the confusion arises by what appears to me to be a modern term, silver brazing. When I worked for a living, we only had either silver solder of various silver content or brazing rods.

Paul.
I agree Paul, that's the way I learned it as well.

This is only speculation on my part, but I suspect the term "silver brazing" may have come about as a way to differentiate the lower melting temperature silver solders, which can be used with conventional soldering irons, from the higher melting temperature silver alloys which would typically require a propane or butane torch to get enough heat.

Tim
 

robmort

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This makes no sense to me. It states that in brazing, you do everything possible to promote capillary attraction and if this is not done, you are brazing.

Or am I reading this wrong?

Bill
You are indeed reading it wrongly. It clearly said
"........if this is not done, you are not brazing"
 

GWRdriver

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This is only speculation on my part, but I suspect the term "silver brazing" may have come about as a way to differentiate the lower melting temperature silver solders, [snip]
Tim,
While it may only apply to a very small percentage of the population, even the steam model building population, I know it to be more than speculation and my first post ( #8 ) gives a good example of it.
 
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Entropy455

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It appears this will be a case of irresolvable semantics


What’s interesting is that when I search for the 76315 Harris part number, I find a brazing alloy – not a silver solder (see pic). Perhaps Harris labeled your package specifically for overseas sales?

For folks on these boards who require just a bit further clarification:

If you take a piece of 1/16” diameter Harris “silver solder” and wrap it around your hands & pull it apart – it will take about 25 pounds of force to break it (about 8,200 psi tensile strength - typical). If you take a piece of 1/16” diameter Harris “silver braze” and wrap it around your hands & pull it apart – it will take between 122 pounds to 214 pounds of force to break it – depending on the particular alloy (40,000 psi to 70,000 psi tensile strength typical).

And shear strength of a material is related to the ultimate tensile strength of the material. This means that if you assemble a copper boiler with “silver solder” the joints will be at a minimum of 5 times weaker in shear, than if you had used a proper silver brazing alloy. And when you take into account the fact that silver solder loses appreciable strength at elevated temperatures, your hobby boiler becomes a potential bomb while in operation. And for the record - Harris part number 76315 is in fact a silver brazing alloy, despite the "silver solder" labeling on the container that GWRdriver posted within a pic on page 2 of this thread.
 

GWRdriver

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If you take a piece of 1/16” diameter Harris “silver solder” and wrap it around your hands & pull it apart – it will take about 25 pounds of force to break it [snip] This means that if you assemble a copper boiler with “silver solder” [snip] your hobby boiler becomes a potential bomb while in operation.
Complete nonsense.
 

Entropy455

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Complete nonsense.


In my profession, when you say that someone’s position is complete nonsense, it is customary to explain why. Let’s try something – I’ll post information, then you specifically identify and correct any nonsensical errors. Can you do that?

Cadmium-free 45% silver brazing alloy typically melts just under 1400 degrees F. A brazed butt-joint on copper with 45% silver, will typically have a joint tensile strength around 33,000 psi. A brazed butt-joint on brass with 45% sliver, will typically have a joint tensile strength of between 35,000 and 45,000 psi – depending on the brass alloy. Butt-joints are appreciably strong using this alloy, where the base material usually fails in lieu of the brazing alloy failing. Additionally, the increased shear-area of lapped-joints using 45% silver virtually guarantees that any joint failure will occur within the base material. A 100 psig hobby boiler (containing 338 degree F saturated steam) will be operating 1000 degrees less than the melting temperature of the brazing alloy.

Typical tin-silver soldering alloy (96/4) melts around 430 degrees F. A soldered butt-joint on copper or brass using “silver solder” will typically have a joint tensile strength under 14,000 psi. The tensile strength of the solder is less than that of brass and copper, thus the only way to achieve a strong joint is by utilizing very large lap-joints. A lap-joint using this alloy will achieve 11,000 psi shear strength (typical). A 100 psig hobby boiler (containing 338 degree F saturated steam) will be operating 92 degrees less than the melting temperature of the soldering alloy.
 
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goldstar31

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Perhaps a moderator could end what has been a nice balanced discussion but has now degenerated into something where the poster is probably being blinded with science. Unquestionably good joining has and will be carried out and which if safety is demanded, there will be boiler examiners and regular subsequent re-tests to ensure safety.

Norman Atkinson
 

Entropy455

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Goldstar31, do you really think it’s safe to construct a copper boiler, where the saturated steam temperature is only 92 degrees F away from melting the solder alloy?

I visit these boards as a hobby. I usually only browse, however I’ll chime in whenever I see someone posting potentially dangerous advise.

This fall I’m taking the final written examination required for obtaining my Professional Engineering License (the end of a tedious 8 year long process) – at which point I’ll able to certify various engineering designs (including boiler design), in the interest of public safety, on behalf of the great State of Washington.

It's my business and obligation to dive deep into the science, which is why I take your criticism as a complement. . . .
 

GWRdriver

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Goldstar31, do you really think it’s safe to construct a copper boiler, where the saturated steam temperature is only 92 degrees F away from melting the solder alloy?
No one, not myself nor anyone else has even remotely suggested that this is in any way acceptable practice. In fact just the opposite is true. Continuing to muddle things simply to win the point is making this thread less educational, rather than more so.
obtaining my Professional Engineering License (the end of a tedious 8 year long process) – at which point I’ll able to certify various engineering designs (including boiler design), in the interest of public safety, on behalf of the great State of Washington.
Now I see where this is coming from. You should not make the mistake of assuming that no one save yourself knows anything about the science nor has an interest in the protecting the "health, safety, and welfare" of the general public (the way the US law usually reads.) We do. Another thing we know is that we never know who is reading what we write. Responsible live steamers in every country go to great lengths to educate and self-police in order to preserve our 100% record of boiler safety. When one individual, either uninformed or in search of notoriety, posts hyperbolic words such as "bomb" or "missile" or "shrapnel" in connection with model boilers I cringe because there's no telling who is reading those words. If read by some misguided and overzealous official, this could put all our decades of good works in jeopardy.

BTW, there have been deaths associated with amateur live steam activities, all in the operation of "full size" equipment. One incident that comes immediately to mind was the accidental release of steam from a vertical steam launch boiler which killed two in the UK. The inquest found that the accident was caused during a certification inspection and steam test by the improper replacement of an inspection port gasket which was the responsibility of the "experienced" inspecting engineer. Congratulations on soon obtaining your ticket (I got mine about 40 years ago.) Hopefully you will come to see that it's power isn't in what you can to do TO other people, but in what you can do FOR other people.
 
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Entropy455

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Hopefully you will come to see that it's power isn't in what you can to do TO other people, but in what you can do FOR other people.
Why do you assume that I’m seeking my professional engineering license for vengeful purposes? That’s such a strange and bizarre comment to make. Engineers use their stamp for profit. An engineer that’s overbearing and unhelpful to his customers is going to lose business in a rapid fashion. I am curious as to why you, a licensed professional engineer, would identify himself as a retired architect. Which state did you get your stamp in? In which field of engineering did you obtain your degree? Or are we not talking about the same ticket?

On post 24, I commented that it’s unsafe to use silver-solder in constructing a copper boiler. Then on post 26 you said it was complete nonsense - which can only be inferred that you believe the opposite to be true. So which is it???
 

dnalot

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This is the sort of thing I don't come here for. Think I will take a week off.

Mark T
 

rick9345

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one is an authority while being paid to testify(court of law)
rest of the time it is just an opinion
everyone has one
RESPECT
 

Hopper

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Getting back to the original topic, I think the solder/braze terminology may have varied over time as well as over geography.

My 1941 Machinery's Handbook refers to "hard-soldering" and "brazing" as interchangeable terms, but qualifies it by saying common useage is:
"Brazing is generally understood to mean the joining of metals by a film of brass, wheras hard-soldering (used by jewellers) ordinarily means that "silver solder" is used. (see silver solders)"

The referred to section on silver solder then goes on to say silver solder is a hard solder used by jewellers and electrical manufacturers and has a silver content in various instances from 49 per cent to 70 per cent.
Quote: "Silver coins can also be used for small work.
..."Silver soldering is employed for uniting comparatively small parts requiring a strong joint."


Then in the section on brazing, it says "The alloys used for brazing are composed of copper-zinc alloys. "
No mention of silver in relation to brazing.

So 50 to 70 per cent silver rods were considered "Silver Solder", in 1941, in the US published Machinery's Handbook.

This was the same thing I was taught both on the job and at trade school as an apprentice in the 1970s in Australia and used all through my working life in the trades here, Africa and the US.

Seems though that today at the local Australian hardware stores, they have labelled "silver brazing" rods of 50 per cent silver etc, and "silver solder" that is 3 or 5 per cent silver and the rest tin. Seems to have been something that came about with the mandate to remove lead from plumber's solder.
 

Entropy455

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The mainstreaming of tin-silver solder was likely a result of the anti-lead movement. Adding further confusion into the mix, is the advent of lead-tin-silver solder (also called silver solder), which is intended to increase electrical conductivity within high-fidelity electronic circuits.

Silver brazed piping joints are to this day widely used in business and industry within low to medium pressure applications. The joints are relatively easy to makeup (no fancy welding equipment), and more importantly, the joints can be disassembled and reassembled without grinding out welds. The high strength of a brazed joint hinges solely on the shear-strength of the brazing alloy. Inadvertently putting silver-solder into a joint that’s holding back 300 degree F pressurized water, or pressurized ammonia, or pressurized gasoline, is a very serious accident waiting to happen. If one were to dive into the historical chapters of ASTMs and the BPVC, I’m sure they’d find references to case-studies where people have died from the use of silver solder within joints intended for use with silver-braze – as there’s a reason why our technical books and references have been rewritten to specifically distinguish between soldering and brazing.

Silver-Tin solder has its place within low-pressure and low-temperature joints, such as potable water copper pipes, open-ended drain and collection piping, and possibly within some HVAC applications also.

Lead-Tin-Silver "silver-solder" belongs on transistor leads.

Silver-Solder alloys have no business whatsoever within high-energy steam joints.
 
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GWRdriver

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[snip]also I notice little gas bubbles in one of my failed welds
In all the hubbub I don't see your question about this answered and I can shed some light on that for you. If by welds you mean silver-soldered joints, with high silver content silver solders bubbling indicates the solder has boiled and that is always the fingerprint of overheating.
Typically overheating arises for one of two reasons, the first being the torch has accidentally been allowed to linger for too long in one place and isolated overheating occurs. The second is very often the result of poor joint preparation, ie, fitting, cleaning and fluxing, or perhaps even the wrong flux, or contamination of the work prior to heating. When you are up to the temperature at which the solder should flash into the joint, but the joint rejects the solder, a common response is to pour more heat into it and hope for the best.
This rarely solves the problem and in fact usually makes matters worse, typically by causing the formation of oxides and/or burning the flux. This can lead to an array of difficult problems, some fatal to the work, such as contaminating joint which can no longer be reached to clean and re-prepare. That is why so much emphasis is placed on joint preparation.
 
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Ripcrow

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Well this is generating a fair amount of debate. At least I'm confused for a reason,you would think that there would be common terms used around the world in engineering .thanks for all your replies
 

goldstar31

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Hello all, I enclose a link to my blog where I have a video explaining silver soldering that might help many

http://www.ahsprite-mk3-restoration.blogspot.com.es/2012/11/six-steps-of-successful-brazing.html
I can understand silver soldering and whatever. I was a certified welder and all that. Again, I have double distinctions in City and Guilds in Motor Vehicle Restoration and trained with the Nissan crowd from Washington, County Durham and have had a Spanish registered car which is due for another ITV this year. I built and restored MiniCoopers, Spridgets, MGB and C's and well, a lot of things. So my questions are valid?

As Spridgets were built with a sort of chassis like the Spits, they were constructed mainly with spot welding- so that they would tear and probably absorb some shock in a collision. Of course, this was before Thatcham and actually counting the specified number of welds in a section in a repair. Certainly, continuous seam welds using the Mig/Mag process have always been frowned on.

How does the ITV in Spain and the appropriate Spanish vehicle insurers regard the rather unusual structural welding system which you appear to have adopted.

Regards,

Norman
 

Hopper

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...If one were to dive into the historical chapters of ASTMs and the BPVC, I’m sure they’d find references to case-studies where people have died from the use of silver solder within joints intended for use with silver-braze – as there’s a reason why our technical books and references have been rewritten to specifically distinguish between soldering and brazing.
.
Ah yes, now that makes a lot of sense. Never was a problem in the old days before this newfangled 5 per cent silver solder stuff existed. But certainly could lead to deadly confusion today.
 
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