I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks

On Jan 22, 4:07*pm, Ignoramus6092
wrote:
I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks

These people are the best source that I know for information on Silver
Soldering.

http://www.lucasmilhaupt.com/en-US/p...illermetals/1/

You have to register to access their brazing book, but I think worth
it. You will be able to see the range of temperatures various silver
brazing alloys melt at.


Dan

Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

Jon

On Sun, 22 Jan 2012 15:17:16 -0600, Jon Elson
wrote:

Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

Jon

Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

The most commonly used silver alloy fror ordinary electrical contacts
is coin silver, which is a binary with 10% Cu. It melts at around
1,430 deg. F.

Silver brazing alloys melt at somewhat lower temps. So, disregarding
the unusual low-temp silver binaries, I'd start at around 900 deg. F
and start raising the temp until you can pop the contacts off of the
copper.

There's a slim chance that they aren't brazed on at all, but just
diffusion-bonded in a furnace. To do that, you'd clean and flux the
contact area between the silver and copper, put them in an oven, and
soak them at around 1,500 deg. until the silver and copper mutually
diffuse and form a thin layer of silver/copper binary alloy. To get
them to separate, you'd want to soak them at the same temperature
again, or slightly higher, and pop off the silver as quickly as you
can, before a bigger area diffuses out.

--
Ed Huntress

On Sun, 22 Jan 2012 16:34:53 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 15:17:16 -0600, Jon Elson
wrote:

Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

Jon

Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

The most commonly used silver alloy fror ordinary electrical contacts
is coin silver, which is a binary with 10% Cu. It melts at around
1,430 deg. F.

Silver brazing alloys melt at somewhat lower temps. So, disregarding
the unusual low-temp silver binaries, I'd start at around 900 deg. F
and start raising the temp until you can pop the contacts off of the
copper.

There's a slim chance that they aren't brazed on at all, but just
diffusion-bonded in a furnace. To do that, you'd clean and flux the
contact area between the silver and copper, put them in an oven, and
soak them at around 1,500 deg. until the silver and copper mutually
diffuse and form a thin layer of silver/copper binary alloy. To get
them to separate, you'd want to soak them at the same temperature
again, or slightly higher, and pop off the silver as quickly as you
can, before a bigger area diffuses out.

Correction: The 1,430 deg. F melting temp for silver/copper is for the
eutectic, which is 28% copper. Coin silver, with 10% copper, melts at
a somewhat higher temperature.

The process would be the same, but it requires a higher temperture to
separate a brazed or diffusion-bonded contact. On the other hand, the
1,500 degrees I mentioned would be too high. Probably between 1,450
and 1,500 should do it, if the bond is diffused. But try lower first,
around 1,400, on the stronger possibility that the joint is brazed
with a lower-temp alloy.

If you soak it too long, you'll create new intermetallic compounds and
you may have a b&%ch of a time getting them apart. Work as fast as you
can.

--
Ed Huntress

On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i

Ignoramus6092 wrote:

On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
In that case, it may be possible to saw off the back part, and then
grind a bit until you hit the silver layer from the back. That will
get the silver out no matter how the thing was made.

Jon

On 1/22/2012 4:07 PM, Ignoramus6092 wrote:
I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks

I just use a Presto-lite torch and replace with either Sterling or Fine
silver plate stock I get from a jewelry making supply store. Use their
soft sheet solder and spray flux.

On 1/22/2012 4:07 PM, Ignoramus6092 wrote:
I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks

I just use a Presto-lite torch and replace with either Sterling or Fine
silver plate stock I get from a jewelry making supply store. Use their
soft sheet solder and spray flux. My contacts outlast factory contacts
many times over.

Ignoramus6092 wrote:
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i


So it costs you 10 bucks in electric current and an hour or so of time
(mine runs $35.00/hr for odd work) To make about 5 bucks?

How about a simpler solution? Take the contacts, clamp them so the
buttons are hanging down. Then hit the back side of the contacts with a
MAPP torch and let the contacts fall off. Might take 5 minutes to do.

--
Steve W.

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
In that case, it may be possible to saw off the back part, and then
grind a bit until you hit the silver layer from the back. That will
get the silver out no matter how the thing was made.

Jon

Grinding copper is mnot exactly fun, do not ask me how I know.

i

On 2012-01-22, Ed Huntress wrote:
On Sun, 22 Jan 2012 16:34:53 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 15:17:16 -0600, Jon Elson
wrote:

Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

Jon

Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

The most commonly used silver alloy fror ordinary electrical contacts
is coin silver, which is a binary with 10% Cu. It melts at around
1,430 deg. F.

Silver brazing alloys melt at somewhat lower temps. So, disregarding
the unusual low-temp silver binaries, I'd start at around 900 deg. F
and start raising the temp until you can pop the contacts off of the
copper.

There's a slim chance that they aren't brazed on at all, but just
diffusion-bonded in a furnace. To do that, you'd clean and flux the
contact area between the silver and copper, put them in an oven, and
soak them at around 1,500 deg. until the silver and copper mutually
diffuse and form a thin layer of silver/copper binary alloy. To get
them to separate, you'd want to soak them at the same temperature
again, or slightly higher, and pop off the silver as quickly as you
can, before a bigger area diffuses out.

Correction: The 1,430 deg. F melting temp for silver/copper is for the
eutectic, which is 28% copper. Coin silver, with 10% copper, melts at
a somewhat higher temperature.

The process would be the same, but it requires a higher temperture to
separate a brazed or diffusion-bonded contact. On the other hand, the
1,500 degrees I mentioned would be too high. Probably between 1,450
and 1,500 should do it, if the bond is diffused. But try lower first,
around 1,400, on the stronger possibility that the joint is brazed
with a lower-temp alloy.

If you soak it too long, you'll create new intermetallic compounds and
you may have a b&%ch of a time getting them apart. Work as fast as you
can.


Thanks. I may want to just scrap them as is.

i

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
In that case, it may be possible to saw off the back part, and then
grind a bit until you hit the silver layer from the back. That will
get the silver out no matter how the thing was made.

Jon

Grinding copper is mnot exactly fun, do not ask me how I know.

i

Of course you do not want to grind copper or other soft metals; they will
just mess up your stone. But sanding with a belt sander works pretty well if
you do not try to remove material too quickly (otherwise the paper heats up
too much.)

On Sun, 22 Jan 2012 20:17:44 -0600, Ignoramus6092
wrote:

On 2012-01-22, Ed Huntress wrote:
On Sun, 22 Jan 2012 16:34:53 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 15:17:16 -0600, Jon Elson
wrote:

Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

Jon

Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

The most commonly used silver alloy fror ordinary electrical contacts
is coin silver, which is a binary with 10% Cu. It melts at around
1,430 deg. F.

Silver brazing alloys melt at somewhat lower temps. So, disregarding
the unusual low-temp silver binaries, I'd start at around 900 deg. F
and start raising the temp until you can pop the contacts off of the
copper.

There's a slim chance that they aren't brazed on at all, but just
diffusion-bonded in a furnace. To do that, you'd clean and flux the
contact area between the silver and copper, put them in an oven, and
soak them at around 1,500 deg. until the silver and copper mutually
diffuse and form a thin layer of silver/copper binary alloy. To get
them to separate, you'd want to soak them at the same temperature
again, or slightly higher, and pop off the silver as quickly as you
can, before a bigger area diffuses out.

Correction: The 1,430 deg. F melting temp for silver/copper is for the
eutectic, which is 28% copper. Coin silver, with 10% copper, melts at
a somewhat higher temperature.

The process would be the same, but it requires a higher temperture to
separate a brazed or diffusion-bonded contact. On the other hand, the
1,500 degrees I mentioned would be too high. Probably between 1,450
and 1,500 should do it, if the bond is diffused. But try lower first,
around 1,400, on the stronger possibility that the joint is brazed
with a lower-temp alloy.

If you soak it too long, you'll create new intermetallic compounds and
you may have a b&%ch of a time getting them apart. Work as fast as you
can.


Thanks. I may want to just scrap them as is.

i

It may not be worth trying to get them apart, but, for the record,
what I would do is this: Heat them to around 1,200 def. F in a heat
treating furnace, or just heat them good with a torch, to a low red
color (maybe 1,200 = 1,300 deg. F). If they're brazed, they'll pop
apart. If they don't, they aren't worth screwing with. I'd just scrap
them as is at that point.

--
Ed Huntress

On 2012-01-23, Steve W. wrote:
Ignoramus6092 wrote:
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i


So it costs you 10 bucks in electric current and an hour or so of time
(mine runs $35.00/hr for odd work) To make about 5 bucks?

How about a simpler solution? Take the contacts, clamp them so the
buttons are hanging down. Then hit the back side of the contacts with a
MAPP torch and let the contacts fall off. Might take 5 minutes to do.


I will do just that, perhaps with O/A instead.

i

On Sun, 22 Jan 2012 20:58:46 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.
I'd just heat the copper backing with my torch until the braze lets
go or the terminal melts

On Sun, 22 Jan 2012 23:45:39 -0500, wrote:

On Sun, 22 Jan 2012 20:58:46 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.
I'd just heat the copper backing with my torch until the braze lets
go or the terminal melts

Yeah, as a practical matter, I agree. And if it all just goes
"schlump," then don't do it again. g

Brass goes "schlump" very easily when you silver-braze it, if the
braze melts at too high a temperature. But copper does not.

--
Ed Huntress

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
Some things you need to know.

Some silver contacts contain cadmium. If the contact does not, the solder
may. Don't do anything with them without a breeze coming from the side, to
carry fumes away from you.

Some silver contacts are not silver along, but sintered tungsten, filled
with silver. They will have a waffle pattern on the back side, obvious
when you remove the contact from the buss. The silver can be leached by
prolonged heating in distilled water and nitric acid. Keep the container
(beaker) covered with a watch glass to prevent losses of values.

Contacts are easily removed by heating with a torch. I've done, literally,
hundreds of pounds of them through my many years of refining precious
metals. Want to get them off easily? Hold the buss with a pliers, while
heating the contact. Apply heat directly on top, and keep watch on the
solder, below. When you see it's molten, rap the buss on the edge of a
coffee can. That dislodges the contact and the bulk of the solder, both of
which will end up in the coffee can. Done.

Don't toss the silver with the base metal. Silver is now over $30 troy
ounce.

Harold

"Ed Huntress" wrote in message
...
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Correction below---changed word from along to alone. Sorry bout that.
Second paragraph, first sentence.


"Harold & Susan Vordos" wrote in message
...

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
Some things you need to know.

Some silver contacts contain cadmium. If the contact does not, the
solder may. Don't do anything with them without a breeze coming from the
side, to carry fumes away from you.

Some silver contacts are not silver alone, but sintered tungsten, filled
with silver. They will have a waffle pattern on the back side, obvious
when you remove the contact from the buss. The silver can be leached by
prolonged heating in distilled water and nitric acid. Keep the container
(beaker) covered with a watch glass to prevent losses of values.

Contacts are easily removed by heating with a torch. I've done, literally,
hundreds of pounds of them through my many years of refining precious
metals. Want to get them off easily? Hold the buss with a pliers,
while heating the contact. Apply heat directly on top, and keep watch on
the solder, below. When you see it's molten, rap the buss on the edge of
a coffee can. That dislodges the contact and the bulk of the solder, both
of which will end up in the coffee can. Done.

Don't toss the silver with the base metal. Silver is now over $30 troy
ounce.

Harold

On Mon, 23 Jan 2012 06:44:50 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
.. .
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Something is very strange here, Harold. Practically every source says
that coin silver is the predominant material for silver electrical
contacts. There is even an ASTM specification for it -- ASTM B617 -
98(2010) Standard Specification for Coin Silver Electrical Contact
Alloy.

--
Ed Huntress

On Jan 22, 11:48*pm, Ed Huntress wrote:

Brass goes "schlump" very easily when you silver-braze it, if the
braze melts at too high a temperature. But copper does not.

--
Ed Huntress

But you will not run into silver contacts brazed onto brass in
switchgear.

Dan

Harold & Susan Vordos wrote:

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
Some things you need to know.

Some silver contacts contain cadmium. If the contact does not, the solder
may. Don't do anything with them without a breeze coming from the side, to
carry fumes away from you.

Some silver contacts are not silver along, but sintered tungsten, filled
with silver. They will have a waffle pattern on the back side, obvious
when you remove the contact from the buss. The silver can be leached by
prolonged heating in distilled water and nitric acid. Keep the container
(beaker) covered with a watch glass to prevent losses of values.

Any tips for separating the silver from the sludge in photographic silver
reclamation systems that use steel wool? The silver dust ends up mixed
with iron and iron oxides and who knows what from the used fixer.

Ed Huntress wrote:
On Sun, 22 Jan 2012 23:45:39 -0500, wrote:

On Sun, 22 Jan 2012 20:58:46 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.
I'd just heat the copper backing with my torch until the braze lets
go or the terminal melts

Yeah, as a practical matter, I agree. And if it all just goes
"schlump," then don't do it again. g

Brass goes "schlump" very easily when you silver-braze it, if the
braze melts at too high a temperature. But copper does not.

heh.

I though it would be fun to try to forge a brass bar once. The thing
collapsed like a piece of solder then grew large cubic crystals where it
fell apart. That was amusing.

On Mon, 23 Jan 2012 21:34:43 +0000 (UTC), Cydrome Leader
wrote:

Ed Huntress wrote:
On Sun, 22 Jan 2012 23:45:39 -0500, wrote:

On Sun, 22 Jan 2012 20:58:46 -0500, Ed Huntress
wrote:

On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.
I'd just heat the copper backing with my torch until the braze lets
go or the terminal melts

Yeah, as a practical matter, I agree. And if it all just goes
"schlump," then don't do it again. g

Brass goes "schlump" very easily when you silver-braze it, if the
braze melts at too high a temperature. But copper does not.

heh.

I though it would be fun to try to forge a brass bar once. The thing
collapsed like a piece of solder then grew large cubic crystals where it
fell apart. That was amusing.

g I have gotten a couple of brass surprises myself, trying to
silver-braze it with some old braze metal of unknown composition. It
worked a couple of times, and then I watched it turn into a bag of
oxide-covered molten brass a couple of other times.

I imaging it's disconcerting to discover that property when you're
trying to forge it.

--
Ed Huntress

Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

I thought pure silver melted at about 1763° F.

Pete Stanaitis
---------------

On Mon, 23 Jan 2012 17:39:27 -0600, "Pete S"
wrote:



Pure silver melts at just under 1,600 deg. F. All, or nearly all, of
the silver binary alloys melt at lower temperatures, down to around
800 deg. F.

I thought pure silver melted at about 1763° F.

Pete Stanaitis

Yup, the type is pretty small in my old handbook. g Thanks, Pete.
I'll use the magnifying glass next time...

--
Ed Huntress

On 2012-01-23, jeff wrote:
On Sun, 22 Jan 2012 22:38:55 -0600, Ignoramus6092
wrote:

On 2012-01-23, Steve W. wrote:
Ignoramus6092 wrote:
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i


So it costs you 10 bucks in electric current and an hour or so of time
(mine runs $35.00/hr for odd work) To make about 5 bucks?

How about a simpler solution? Take the contacts, clamp them so the
buttons are hanging down. Then hit the back side of the contacts with a
MAPP torch and let the contacts fall off. Might take 5 minutes to do.


I will do just that, perhaps with O/A instead.

i
The O/A method will work fine. Have someone poke the silver with a
screwdriver and it will fall off when you hit the proper temp. I
used to do it with all my contactor tips but with the price of gas it
just wasn't worth it anymore.

Where do you take that silver?

i

"Ed Huntress" wrote in message
...
On Mon, 23 Jan 2012 06:44:50 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
. ..
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Something is very strange here, Harold. Practically every source says
that coin silver is the predominant material for silver electrical
contacts. There is even an ASTM specification for it -- ASTM B617 -
98(2010) Standard Specification for Coin Silver Electrical Contact
Alloy.

http://www.astm.org/Standards/B617.htm

I have a 1948 Metals Handbook. Two pages of Coin Silver alloys, with
specific info on contact material, physical characteristics, and how the
metal is worked for contact applications. Two more pages of Silver alloys
for electrical contacts. Silver-Tungsten, Silver-Molybdenum, Silver-Nickel,
Silver-Graphite, Silver-Cadmium, Silver-CdO, Silver-Lead.
The latter seem to be powder metallurgy, sintering and heat treatments. With
paragraphs on specific applications. Eg. Silver-CdO used in WW2 warplane
gunnery switchgear. Charts of how electrical properties vary with alloy
content, etc. Some info on how some contact pairs used different materials
on each side to reduce arcing. Eg Silver-Nickel in one contact and
Silver-Graphite in the other. Seems like 1948 era materials engineering was
more sophisticated than the casual reader would have guessed.

On Mon, 23 Jan 2012 20:33:51 -0600, "bw" wrote:


"Ed Huntress" wrote in message
.. .
On Mon, 23 Jan 2012 06:44:50 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
...
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Something is very strange here, Harold. Practically every source says
that coin silver is the predominant material for silver electrical
contacts. There is even an ASTM specification for it -- ASTM B617 -
98(2010) Standard Specification for Coin Silver Electrical Contact
Alloy.

http://www.astm.org/Standards/B617.htm

I have a 1948 Metals Handbook. Two pages of Coin Silver alloys, with
specific info on contact material, physical characteristics, and how the
metal is worked for contact applications. Two more pages of Silver alloys
for electrical contacts. Silver-Tungsten, Silver-Molybdenum, Silver-Nickel,
Silver-Graphite, Silver-Cadmium, Silver-CdO, Silver-Lead.

Huh. That's interesting. My 1979 edition doesn't have near that much
about it. It just lists coin silver as the primary alloy for
electrical contacts.

The latter seem to be powder metallurgy, sintering and heat treatments. With
paragraphs on specific applications. Eg. Silver-CdO used in WW2 warplane
gunnery switchgear. Charts of how electrical properties vary with alloy
content, etc. Some info on how some contact pairs used different materials
on each side to reduce arcing. Eg Silver-Nickel in one contact and
Silver-Graphite in the other. Seems like 1948 era materials engineering was
more sophisticated than the casual reader would have guessed.

Yes indeed.

--
Ed Huntress

"Cydrome Leader" wrote in message
...
Harold & Susan Vordos wrote:

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
Some things you need to know.

Some silver contacts contain cadmium. If the contact does not, the
solder
may. Don't do anything with them without a breeze coming from the side,
to
carry fumes away from you.

Some silver contacts are not silver along, but sintered tungsten, filled
with silver. They will have a waffle pattern on the back side, obvious
when you remove the contact from the buss. The silver can be leached by
prolonged heating in distilled water and nitric acid. Keep the container
(beaker) covered with a watch glass to prevent losses of values.

Any tips for separating the silver from the sludge in photographic silver
reclamation systems that use steel wool? The silver dust ends up mixed
with iron and iron oxides and who knows what from the used fixer.

Silver and iron won't alloy, so you can melt the sludge with soda ash and
borax. Pour to a cone mold to separate the resulting silver from the slag.
If there's sulfates present, a couple pieces of scrap iron (lengths of rebar
work fine) inserted will ensure that the sulfur liberates any silver that's
combined. In such a case, you'll get three layers in the cone mold, the
top one being slag, the second a sulfide layer, hopefully sulfur and iron,
and the bottom silver. The silver should be of good quality, but can be
parted in a silver cell to ensure purity.

Harold

"Ed Huntress" wrote in message
...
On Mon, 23 Jan 2012 06:44:50 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
. ..
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Something is very strange here, Harold. Practically every source says
that coin silver is the predominant material for silver electrical
contacts. There is even an ASTM specification for it -- ASTM B617 -
98(2010) Standard Specification for Coin Silver Electrical Contact
Alloy.

--
Ed Huntress

Even heavy duty contacts? That's predominantly what I refined. From
switching gear, for instance, not small appliances. Traces of copper
report in the solution, but nowhere near enough to account for the color
you'd expect from coin silver. In fact, the small amount could easily be
determined to be from the solder used to mount the contact.

I have almost no experience with small contacts, so that makes me wonder if,
perhaps, that's the type that may be made of coin silver (90% silver, 10%
copper).

Some silver contacts are alloyed with cadmium. I did encounter a small lot
of those. Amazing how little silver they contained.

Harold

On Wed, 25 Jan 2012 09:15:12 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
.. .
On Mon, 23 Jan 2012 06:44:50 GMT, "Harold & Susan Vordos"
wrote:


"Ed Huntress" wrote in message
...
On Sun, 22 Jan 2012 20:44:08 -0500, wrote:

On Sun, 22 Jan 2012 15:07:52 -0600, Ignoramus6092
wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?

Thanks
About 10 degrees below the melting point of the silver???

But which alloy is he dealing with? Most electrical contacts are made
of coin silver, which melts at a lower temperature.

--
Ed Huntress

Nope. I never encountered coin silver in contacts, not ever.

Harold

Something is very strange here, Harold. Practically every source says
that coin silver is the predominant material for silver electrical
contacts. There is even an ASTM specification for it -- ASTM B617 -
98(2010) Standard Specification for Coin Silver Electrical Contact
Alloy.

--
Ed Huntress

Even heavy duty contacts? That's predominantly what I refined. From
switching gear, for instance, not small appliances. Traces of copper
report in the solution, but nowhere near enough to account for the color
you'd expect from coin silver. In fact, the small amount could easily be
determined to be from the solder used to mount the contact.

I have almost no experience with small contacts, so that makes me wonder if,
perhaps, that's the type that may be made of coin silver (90% silver, 10%
copper).

Some silver contacts are alloyed with cadmium. I did encounter a small lot
of those. Amazing how little silver they contained.

Harold

I suspected that was it, because you certainly know your precious
metals. Coin silver apparently is used for the ordinary types of
contacts, both for consumer and industrial applications, but a variety
of other alloys are used for very high-current or high-voltage
applications.

Some low-voltage applications that require the lowest resistance use
fine silver, too.

--
Ed Huntress

Harold & Susan Vordos wrote:

"Cydrome Leader" wrote in message
...
Harold & Susan Vordos wrote:

"Ignoramus6092" wrote in message
...
On 2012-01-22, Jon Elson wrote:
Ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Man! Without knowing a bunch about the silver alloy and the brazing
alloy, it is pretty hard to know what would be the magic temperature.
If you had a barrel of them, you could do a couple tests to find
the temp.

I only have two, I would say I can make 1-1.5 ounce of silver from the
contacts.

i
Some things you need to know.

Some silver contacts contain cadmium. If the contact does not, the
solder
may. Don't do anything with them without a breeze coming from the side,
to
carry fumes away from you.

Some silver contacts are not silver along, but sintered tungsten, filled
with silver. They will have a waffle pattern on the back side, obvious
when you remove the contact from the buss. The silver can be leached by
prolonged heating in distilled water and nitric acid. Keep the container
(beaker) covered with a watch glass to prevent losses of values.

Any tips for separating the silver from the sludge in photographic silver
reclamation systems that use steel wool? The silver dust ends up mixed
with iron and iron oxides and who knows what from the used fixer.

Silver and iron won't alloy, so you can melt the sludge with soda ash and
borax. Pour to a cone mold to separate the resulting silver from the slag.
If there's sulfates present, a couple pieces of scrap iron (lengths of rebar
work fine) inserted will ensure that the sulfur liberates any silver that's
combined. In such a case, you'll get three layers in the cone mold, the
top one being slag, the second a sulfide layer, hopefully sulfur and iron,
and the bottom silver. The silver should be of good quality, but can be
parted in a silver cell to ensure purity.

Harold

Awesome tip. I've looked on photo forums and found nothing of value. The
dissolve the silver in acid and precipite it methods don't seem applicable
as iron will dissolve in those acids, and buying huge tanks of nitric
acid doesn't seem worth the effort considering the extra hazards.

I've been sending the used fixer to a lab with an electrolytic cell, so
they keep the silver, but it's more of a hassle for them once you factor
in transporting the stuff and returning the containers.

How much soda ash and borax should be used?

I did notice a hydrogen sulfide smell when steel wool is thrown into the
fixer tank. I'm not really clear on when it's ok to stop adding steel wool
as nobody has any idea how much silver is in the spent fix to start with.
One guide mentioned upto an ouce of silver per gallon. I suspect I need to
get some silver test strips to make sure the leftover liquids are safe
enough to dump. One doc says there can be upto an ounce of silver per
gallon of used fix, but until the silver is removed, I have no way to see
how accurate this is.

replying to Ignoramus6092 , hep2it wrote:
ignoramus6092 wrote:

I have a couple of medium voltage switchgear contacts, with seemingly
silver buttons brazed to them. I have a little heat treating oven. How
can I use it to unbraze the buttons, to what temperature should I set
it?
Thanks


I know this is a very old thread, but all I did to remove my silver was
take a sharp chisel, a hammer, and a vise and the contacts just popped
right off. I had a wide variety of contacts, so some removed easier than
others, but all of them came off without too much trouble. Just make sure
you use a chisel that you don't care about.

--
posted from
http://www.polytechforum.com/metalwo...ct-532694-.htm
using PolytechForum's Web, RSS and Social Media Interface to
rec.crafts.metalworking and other engineering groups

replying to Steve W., rizarecta07 wrote:
Nope doesnt work that well. Ive done it. Not hot enough

--
for full context, visit https://www.polytechforum.com/metalw...ct-532694-.htm

replying to Ignoramus6092, Brown wrote:
Be careful, some of the older contacts had cadmium as part of the alloy. Most
of the refiners I talked to would not deal with them.I have several pounds of
contacts still attached to a small portion of brass. I would like to find some
one to buy them.

--
for full context, visit https://www.polytechforum.com/metalw...ct-532694-.htm