Re: granulation

On Thu, 26 Apr 2007 00:31:26 -0700, in rec.crafts.jewelry mbstevens
<NOXwebmasterx@xxxxxxxxxxxxxxx> wrote:

On Thu, 26 Apr 2007 06:08:24 +0000, Peter W.. Rowe, wrote:

It's the same type of bond
produced by brazing, of course, but that's not really a valid label for it,
since no external bonding alloy is formed, if the gold does not melt.

I'm not sure I follow your point on this. When you braze steel, the steel
does not melt.


No, but with brazing steel, you've introduced a third brazing alloy. That's the
point. The bond takes place because a third alloy melts, flowing by capillary
action between the two still solid surfaces, both wetting them, and also bonding
to them. That's what happens with brazing. If, in your gold/silver
granulation, a third alloy is formed at the interface, distinct from either the
gold or the silver, then in metallurgical terms, a certain similarily exists.
But even in that case, the third alloy is formed by the interaction of the two
metals in contact with each other, which is NOT what the term brazing usually
describes, even if the end bond has similarities.


The bronze does move into any porosity in the steel (I
have seen photomicrographs of this), but the main bond is still metallic,
not mechanical, according to all sources I've come across.

Well, both. The penetration of porosity forms a mechanical bond, to be true.
But diffusion of the copper alloy into the steel, even if only slight, as well
as atomic bonds forming between atoms of iron and copper, etc, mean there is
also that metallic bond as well. The degree to which atomic bonding (metallic
bonding) occurs depends a lot on the difference in melting points. Because the
iron melts a LOT higher than does the brazing alloy, the diffusion depth, and
degree of metallic bonding that can take place, is limited to a very narrow
interface zone, and the difference in strength between a metallic bonded surface
and one that is just mechanical, or based just one wetting of the the one
surface with the other (like a glue), is probably not that much. You can
illustrate this difference by soldering/brazing a wire onto a piece of metal
with varying solders. With the lowest melting brazing or soldering alloys, it's
sometimes possible to just peel the wire away, like opening a sardine can,
breaking the bonds, but not the wire. Platinum soldered to gold or even more,
using gold solder, is a good illustration of this, as is platinum soldered to
itself just using the lowest grades of platinum solder. With a joint like this,
there may be some diffusion taking place at the joint interface, but it's so
slight in depth that for all intents and purposes, it doesn't do much more than
wetting the surface the same as a glue would do. Soft solder (lead solders,
etc), also fall into this catagory. Although they are metals too, and potential
alloys exist between the bonded surfaces and the metals in the soft solder, the
differences in melting point are so great as to confine the bond to a narrow
contact zone, thus limiting it's strength.
..

So then,
perhaps neither welding, nor brazing, is accurate. Rather, then fusing would be
most accurate.

However, I'd guess that when the silver melts, the gold surface in contact with
it at least slightly melts too, forming a thin layer of eutectic alloy.

I don't know about that. The metal used on that ring seemed to have a
very much, much higher melting point than sterling. If you're interested
in specifics, I seem to remember the granules were from a Krugerrand. At
any rate, none of the granules have fallen off after much hard use.

I'd expect that. Among other things, silver and gold are totally soluable in
each other. So diffusion zones can form that do not have lots of stress in
them. With copper, because it's much less soluable in either gold or silver at
room temp, diffusion zones/bonds can tend to be hard and sometimes prone to
cracking from the stresses that can build up as a result. That wouldn't be
happening here, so your bonding would likely be quite strong.



In jewelry use, brazing is a term seldom used.

Yes. It should be, but is not. I like to use brazing because it can
never be confused with soft soldering.

It's been said that each profession develops it's own vocabulary to talk to
itself, in part because it must, but also in part to build exclusivity between
it, and outsiders. Nobody ever said it had to make sense, and the English
language is rife with examples of words used in one context differently from in
other contexts, with no apparent logic other than convention. In this case,
while it's technically correct to use the word brazing to describe jewelry hard
soldering, you're setting yourself in a rather small minority, apart from the
conventional usage. In our field, soft soldering is distinguished by using
extra terms, ie "soft", or "lead", rather than the word "soldering" itself.
Again, no real logic, but on the other hand, jewelers themselves don't seem
confused on the issue... For one thing, there's often the issue of non-verbal
communication aiding things, since when talking about soft, or lead, solders,
most jewelers also communicate a sense of disgust, regret, or disdain for the
inferior method and material, again removing doubt as to what's being
discussed...

(grin)



The term "fusing" is not
especially specific. It does not require both surfaces to be the same, or both
to actually melt. All it requires is that two surfaces or items melt together
to form a bond. One can melt, or both can melt, so long as they join in the
process.

I've heard that applied to the adhesion of enamel to metal, and agree
that it must be a good general term. However, in the case of this ring, I
still think 'brazing' is a bit more specific and accurate, if nothing else
because it is metal to metal and very probably a metallic bond.

Mike, welding is also metal to metal, and so is soft soldering, and so is
brazing, etc etc. And in all cases, even including lead solder, there is also
that metallic bond. That's not a useful distinction. All these bonds are at
least in part, a metallic bond. The useful distinction is the source of the
alloy that has flowed between the surfaces to be bonded. Does it come from the
parent metals themselves, either just one surface melting onto the other or both
surfaces combining and melting together? Or does it come from a seperate,
externally applied alloy? THAT's the distinction being made. The end result
bond type is "metallic", essentially the same in all these instances even if
specific details of bond layer or composition, etc differ. . Brazing, as with
jewelers hard soldering, implies the ADDITION/introduction of solder/brazing
alloy in some form to the joint, rather than the formation of a bond from
existing metal. Welding or fusing do not require that addition, (though welding
often needs it for a good weld geometry). You're fusing the grains on, not
soldering or brazing them.

Peter
.

Relevant Pages

  • Re: granulation
    ... while it's technically correct to use the word brazing to describe jewelry hard ... soldering, you're setting yourself in a rather small minority, apart from the ... because it is metal to metal and very probably a metallic bond. ... parent metals themselves, either just one surface melting onto the other or both ...
    (rec.crafts.jewelry)
  • Re: granulation
    ... alloy that has flowed between the surfaces to be bonded. ... THAT's the distinction being made. ... I don't think that is how it is applied, because brazing can be applied ... the other which does not melt, and forms a bond. ...
    (rec.crafts.jewelry)
  • Re: granulation
    ... Welding simply mixes the metals making them one chunk of metal. ... though the difference between this and brazing is that the two ... since no external bonding alloy is formed, if the gold does not melt. ...
    (rec.crafts.jewelry)
  • Re: granulation
    ... Welding simply mixes the metals making them one chunk of metal. ... though the difference between this and brazing is that the two ... since no external bonding alloy is formed, if the gold does not melt. ...
    (rec.crafts.jewelry)
  • Re: granulation
    ... Welding simply mixes the metals making them one chunk of metal. ... though the difference between this and brazing is that the two ... since no external bonding alloy is formed, if the gold does not melt. ...
    (rec.crafts.jewelry)