Subject: Silver Solder? Hard Solder?

From: [email-masked] (Bob Neidorff)
Date: Thu, 4 Nov 1993 15:34:03 GMT

I have some silver braze material.  It seems to be 50% silver
and melt at approx. 1160F.  Brass brazing rods seem to be 
specified as melting at approx. 1350F and up.  Tin-lead solder
is a 360F melting point material.

I find that the brass and silver brazes are too hard to flow,
ie: they take too much torch heat, yet the soft solders are too
weak to use for things which will experience stress.

I see a material advertised which is a silver-bearing solder
that is 96% tin and 4% silver.  The manufacturer claims 4 times
stronger than tin/lead solder and 430F melting point.

Also, there is a product which is 97.5% lead, 1.5% silver and 1% tin.
This is listed as useful where a second solder joint will be required.
It melts at 588F.

Are either of these last two solder products the strong solder that
I am looking for?  Anyone have experience which they can share? 

I don't have oxy-acetylene equipment, but have MAP gas and Propane.
I also have a swirl-combustion torch which can heat some small parts
up to low brazing temperatures, but only after a long time.  No fun.

Thanks for any advice.

I will summarize any replies if there is interest.

-- 
Bob Neidorff; Unitrode I. C. Corp.  |  Internet: [email-masked]
7 Continental Blvd.                 |  Voice   : (US) 603-424-2410
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-424-3460

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From: [email-masked] (John Kopf, X6305)
Date: 5 Nov 1993 20:25:22 GMT

the "silver-bearing" solder is a "soft solder";  it has about the same
strength as ordinary lead solders -- the silver is added PRIMARILY for
improved conduction in electrical work, NOT strength.

True "silver solder" does melt at the range you specified (~1160F).  However,
it available in a number of different alloys, which melt at different 
temperatures.  These are distinguished by terms such as "easy" and "hard"
refering to the *ease of melting* (not strength or "hardness) -- the actual
temperature range may vary by 50F between neighboring alloys.

They're normally used for "progressive" soldering...first with the "hard",
then add more pieces with the "easy" (at a lower temperature, you can melt
the "easy" without remelting the "hard").

I've found that "easy" can be soldered with a propane torch, given reasonably
small mass of material to heat.  If you can, build an "oven" of fire-brick
around the piece to help contain the heat.

JK

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From: Jim Jaskie <[email-masked]>
Date: Thu, 4 Nov 1993 18:00:05 GMT

Subject: Silver Solder? Hard Solder?
From: Bob Neidorff, [email-masked]
In article <[email-masked]> Bob Neidorff,
>I will summarize any replies if there is interest.

Bob, I thought I'd take a moment to add a couple of comments.  I spent
some time on the same task you're looking at.  I came to the conclusion
that my goals of a low-temperature (propane torch) strong solder/braze
was contradictory.  The problem arises not from the strength of the
solder/material but from the low temperature.  At a low temp, there is
very little diffusion or alloying occuring.  Hence, even a very hard
solder does not bond well with steel unless the temperature is hot enough
for the atoms in the steel to migrate, diffuse, and eventually bond with
the solder.  This cold bond of hard material breaks easily and then
people complain about the adhesion of these solders.  Same problem,
different side.

I eventually gave up and moved on to oxy-acethylene and became a fanatic
brazer(sp?).  I learned to braze with "German Silver" (no silver in it,
the name must be an insult from the first war).  Great stuff.  It makes a
bond that is actually stronger than the base low carbon steel, and at a
much lower temp than welding, but high enough for diffusion.  I know,
because I made up test coupons, took them down to the metallurgists lab
at the local University and we tested them.  Easier than gas welding and
stronger.  Slightly more expensive, but not meaningful in the scale of
things for a home shop.  The problem then was all the heat distortion.  I
could never master the art of brazing or welding a nut  without ruining
the threads or shape.  Finally gave up and got a mig welder like the
people who know what the heck they're doing do in the first place.

Let us know if you find something that bonds strongly and is strong, but
has a low application temperature.

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From: [email-masked] (James Foster x2912)
Date: Thu, 4 Nov 1993 19:31:09 GMT

In article <[email-masked]>, [email-masked] (Bob Neidorff) writes:
|> 
|> I have some silver braze material.  It seems to be 50% silver
|> and melt at approx. 1160F.  Brass brazing rods seem to be 
|> specified as melting at approx. 1350F and up.  Tin-lead solder
|> is a 360F melting point material.
|> 
|> I find that the brass and silver brazes are too hard to flow,
|> ie: they take too much torch heat, yet the soft solders are too
|> weak to use for things which will experience stress.
|> 
|> I see a material advertised which is a silver-bearing solder
|> that is 96% tin and 4% silver.  The manufacturer claims 4 times
|> stronger than tin/lead solder and 430F melting point.
|> 
|> Also, there is a product which is 97.5% lead, 1.5% silver and 1% tin.
|> This is listed as useful where a second solder joint will be required.
|> It melts at 588F.
|> 
|> Are either of these last two solder products the strong solder that
|> I am looking for?  Anyone have experience which they can share? 

If you're asking "are these silver solder?" then the answer is no.  The
silver brazing wire or rod you have is silver solder.  The other 
solders may be stronger than straight tin/lead but won't be as 
strong as the silver solder.  

If you're trying to braze larger brass or steel parts then you need
a lot of heat.  A larger compressed air/propane torch can do a pretty
good job.  Air/acetylene is better still.  To really get things up
to brazing temperature in a reasonable time you need to use oxy/something
IMHO.  The something can be propane or acetylene.  A larger torch 
head will help too.

Get the parts clean and as good a fit on the joint as you can.  Use
a good brazing flux and make sure the entire joint area is sufficiently
heated.  If your silver brazing is in rod form then you might want to
buy some in wire form instead.  This won't remove heat as fast from the
joint when it's applied.  If the joint is relatively small then you
can also flatten out the rod or wire with a hammer and anvil and cut
off pieces of the flattened material and put these around the joint
area (when the flux melts it will help hold them in place).  Then the
whole area is heated till the braze flows.  You can often get a very
clean joint using this technique.

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From: [email-masked] (Len Moskowitz)
Date: 5 Nov 1993 14:02:32 -0500

>I am looking for?  Anyone have experience which they can share? 

I join a brass part and a zinc plated plated part with the silver
bearing solder (2%) using a standard electronic soldering iron.  Where
the standard electronic solders wouldn't hold up under load, the silver
bearing solder never lets go.

Most of the solder manufacturers sell a version of this.  Radio Shack
even sells rolls of the stuff for around $4.  It has the flux in it.

-- 
Len Moskowitz
Core Sound
[email-masked]

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From: [email-masked] (f.w.kerfoot..iii)
Date: Fri, 5 Nov 1993 22:54:42 GMT

>From article <[email-masked]>, by [email-masked] (John Kopf, X6305):

While we are on the subject of silver solders, does anyone know about
any legal issues with selling silver solders containing cadmium? When
I started building my live steamer I bought a 1 oz coil of Easy-Flow
45 (if I recollect), as suggested by all of the books I had read.
It contained cadmium.  It worked just fine, once I learned the art.
When I got to the boiler several years later, I quickly used up the 1 oz
coil, so I went back to the welding shop. They only had cadmium free
silver solder. Not knowing any better, I got 1 oz of 45% silver,
cadmium-free solder. It worked much more poorly for my applications.
Clearly the cadmium played a significant role in the melting temp,
and, it appeared, in the wettability. I checked with several other
welding shops (in central NJ), and no one sold anything but cadmium
free solder- they all made a safety arguement (which I understand
is a real issue with the cadmium-). I couldn't tell if they weren't
allowed to sell cadmium bearing solder, or if there wasn't enough
market, of if they were just covering their butt, liability-wise.
In any case, I bought 56% cadmium-free, and finished the boiler with
that. The 56% cadmium-free still does not seem as easy to use as the
45% cadmium bearing solder, but I had resigned myself to not
being able to get cadmium bearing solder. Now, I notice that
McMaster-Carr sells it (but in 5 oz spools, for ~$100). Is cadmium
bearing silver solder generally available, and I just need to
look harder? I don't really need 5 oz, or a bill for $100.

By the way- the reason I am not all that worried about the cadmium
is that I use it perhaps once or twice a month, and I do it
outside, or at least in the (open) doorway of a garage.

Frank Kerfoot
[email-masked]

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From: [email-masked] (John Kopf, X6305)
Date: 9 Nov 1993 20:15:30 GMT

In article [email-masked], [email-masked] (f.w.kerfoot..iii) writes:
> (much deleted).

A local "rockhound"/Lapidary store sells silver solder in small quantities
for jewelery making -- I think at prices which are related to the current 
price of silver.

In any case, for small quantities, look for other, local sources

JK