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Laser welds as compared to soldered joints


#1

There has been some discussion in Orchid on the comparative
strengths of laser welds to soldered joints. Thought some people
might like to read this study complete with micro-photography.

http://www.platinumguild.com/files/pdf/V5N6W_laser_welding.pdf


#2
There has been some discussion in Orchid on the comparative
strengths of laser welds to soldered joints. Thought some people
might like to read this study complete with micro-photography. 

I want to thank Gary for providing the link to the article. Not
because the article demonstrates superiority of laser weld. Actually
it does not do anything of a kind. But it gives me the opportunity
to show how logical fallacies are used to create an appearance of
sound argument, when nothing can be further from the truth.

I begin with quote from the article

“Though these and parallel silver alloys are termed gold or silver
solders, they are by definition, brazing alloys”

This is inaccurate at best. The difference between soldering alloys
and brazing alloys is in application and not in composition. It is
more common to encounter zinc in brazing alloys than in soldering,
but it is not a definitive difference. The above quote is false, but
it is necessary for the author to set up his argument.

Article further defines brazing as

“brazing is a welding process wherein a joint is produced by heating
to a suitable temperature and using a filler metal”

We can stop right here. The rest of the article is a comparison
between welded joints produced with brazing technique, and welded
joints produced with laser. Just because author calls it soldering,
it does not make it so.

The difference between soldered joint and brazed joint is that in
brazing solder used as filler, but in soldered joint, the solder
plays quite different role. It is this particular function of solder,
that makes soldering so superior to any other methods.

So the lesson here is that it is very important to read carefully and
analyze what is actually been written. The author of the article sets
up a premise that soldering and brazing is the same, which is false.
And on the basis of the false premise an argument is built, which
looks impressive upon cursory examination, but falls apart at the
very first reading.

Leonid Surpin
www.studioarete.com


#3

Thank you Gary.

I see under Results on page 26 of the report that the laser welds
did survive the Bend testing, while none of the soldered, or brazed
joins survived this test. This certainly supports my non scientific
work experience, using both methods of joining.

Jim


#4
I want to thank Gary for providing the link to the article. Not
because the article demonstrates superiority of laser weld.
Actually it does not do anything of a kind. But it gives me the
opportunity to show how logical fallacies are used to create an
appearance of sound argument, when nothing can be further from the
truth. 

Why did I know you would try to tell us the in paper is
wrong? One of the authors, Tino Volpe is a friend of mine. He is a
metallurgical engineer and a very contentious researcher. This paper
is good solid work on the subject, with micrographs and physical
tests that support the strength of laser welds compared to brazing
(soldering). Your arguments about differences between soldering and
brazing are specious. You just don’t seem to be able admit that you
are wrong about this topic.

James Binnion
James Binnion Metal Arts


#5

Hi Leonid, Errr…

In the US, brazing and soldering have rather different definitions
in industrial & scientific usage than they do in jewelry trade
usage.

The short answer is that what metalsmiths call “silver soldering” or
"hard soldering" is actually silver brazing. We’ve just been calling
it soldering among ourselves so long that we’ve kept using the wrong
terms. The distinction between soldering and brazing is one of
temperature.

In industrial usage (Like the article Gary linked to) solders are
alloys that melt somewhere between 200-800 f. (90-450 c) There are
various issues with how they bond, due to the low temp, but that’s
what they’d be talking about. Low temp alloys of almost no
appreciable use in jewelry. Fatally weak joints too, BTW.

Brazing refers to any process that uses a molten filler metal that
melts above 450 c, and yet substantially below the melting point of
the target metal.

That would be what we jewelers normally call soldering. We’re wrong,
it’s actually brazing. The distinction between brazing and soldering
is entirely based on temperature range. Composition of the filler is
totally irrelevant.

Welding refers to processes that join the parent metal via processes
that operate at or above the melting point of the parent metal. They
may (or may not) introduce filler metals of similar metallurgical
properties to the parent metals. The main distinction is that in
welding, some of the parent metal does indeed melt and flow into the
joint area. In brazing, the parent metal stays intact and does not
flow.

Regards,
Brian.


#6

I think we’re all trying to fit silver soldering into a definition
tat doesn’t fit.

Unlike soft soldering with lead, brazing with a filling material and
tack welding silver solders form eutectic bonds when they are done
correctly. That is to say that the silver/copper solder diffuses
into the silver on either side of the joint as well as filling the
minute gap. As the heat continues the copper molecules (and zinc if
there are any) migrate so that there is a gradient from the
sterling/fine silver to the solder join and back again to the main
material.

It’s this graduated join that gives the strength to the silver
soldered joint - and weakens the structure of silver in a lead based
joint.

When brazing and welding are done for the right lengths of time and
with the right materials they also can make these types of joint.

Tony Konrath


#7

I believe that what most jewelers call soldering is actually brazing
as the definition of brazing is soldering over 450 degrees. The
solder used in this article were platinum 1700 solder and platinum
1200 solder not 'Brazing material". Another source of great laser
welding to soldering comparisons is the dental industry. The
techniques are virtually the sam e to the jewelry industry.

http://tinyurl.com/yhyfmf4

This one compares silver soldering using silver solder.

Gary


#8
"Though these and parallel silver alloys are termed gold or silver
solders, they are by definition, brazing alloys" This is inaccurate
at best. 

Brazing is a metal-joining process whereby a filler metal or alloy is
heated to melting temperature above 450 C (840 F) and distributed
between two or more close-fitting parts by capillary action.

http://tinyurl.com/ykjnh9z

and more…

http://www.materialsresources.com/mritech/mritech.htm
http://tinyurl.com/aztcz

The International Standard difference is 450 C, the traditional
(meaning obsolete)difference is 425 C (800 F). For fillers that
melt above this= temperature, it is considered brazing. For fillers
that melt below this temperature, it is considered soldering.
Arbitrary, yes, but it is what Mankoand other reference books have
always defined as the difference 

Manko is Howard H. Manko, an illustrious engineering educator, BTW
Gold, silver and platinum soldering is called that by tradition and
convention, but it is brazing in every sense of the word. All the
rest is simple BS.


#9

Hello Leonid,

I am trying to understand this long-running controversy. You and
others seems to have much and understanding, even though
you all don’t always agree.

In your recent post you wrote;

The difference between soldered joint and brazed joint is that in
brazing solder used as filler, but in soldered joint, the solder
plays quite different role. It is this particular function of
solder, that makes soldering so superior to any other methods. 

Your conclusion, which may be perfectly correct for all I know,
might be easier for me to accept if you could please complete the
thought. Can you please explain what is the "quite different role"
that solder plays and how is it different than the role which brazing
alloys play?

Obviously they both fill the joint and they both adhere in some
fashion to the base metals. So exactly how do they differ in their
action?

Thanks if you can fill in this blank for me.

Marty Hykin in Victoria where I braze and solder OK even if I don’t
know the difference.


#10
This paper is good solid work on the subject, with micrographs and
physical tests that support the strength of laser welds compared to
brazing (soldering). Your arguments about differences between
soldering and brazing are specious. 

Here is the problem:

In this article he describes that brazed joint after breaking had
whitish film, as opposed to laser joints been bright. This whitish
film is the tell-tell sign of joint heated on one side only, and
separation takes place on the cold side. In other words, what he
describes is a cold soldered (or more accurately brazed) joint.

Incidentally, properly soldered joint stronger than surrounding
metal and cannot be broken. What breaks is metal in proximity of a
joint.

About speciousness of distinction between soldering and brazing. Here
is the quote from the very best source of the subject:

"in a well made solder joint, especially in precious metal
alloys, the solder flows into the structure of the workpiece.
the parent metal is heated to a temperature at which its grain
structure is open, allowing the solder to be drawn into the
microscopic openings by capillary action as soon as it fluid.
more than that, the solder dissolves the metal it is attaching,
creating the situation, in which a new alloy is formed alongs
the edges of the seam. each time the joint is reheated this
process goes further, with the result that an early seam on a
piece that goes through several heating has a fully homogenized
blending that cannot be detected even with magnification." 

The author of the above quote is Erhard Brepohl, and the work is The
Theory and Practice of Goldsmithing, page 294, ISBN 0 9615984 9 2.
Different printing may have different page number. I have omitted
reference to diagrams used in the text. So as you can see, there
cannot be any whitish film or discoloration of any kind.

You just don't seem to be able admit that you are wrong about this
topic. 

You are arguing not with me, but with Brepohl and thousands upon
thousands of goldsmiths before him. I am just a messenger. Brepohl
text has been published for many years and in many languages, and
probably the most researched, tested, and proven text on the planet
Earth.

You can see practical demonstration of how such joints are done on
my DVD. Here is the link http://www.studioarete.com/eternityring.html

Leonid Surpin
www.studioarete.com


#11
Another source of great laser welding to soldering comparisons is
the dental industry. The techniques are virtually the sam e to the
jewelry industry. 

Not to be repetitive, but in as few words as possible

Capillary action = soldering
solder used as filler = welding

brazing vs welding - that is where classifying by temperature
probably makes sense.

Leonid Surpin
www.studioarete.com


#12
That would be what we jewelers normally call soldering. We're
wrong, it's actually brazing. The distinction between brazing and
soldering is entirely based on temperature range. Composition of
the filler is totally irrelevant. 

In my reply to Jim, I said why do I make the distinction. I am
familiar with definition that you refer to, but it is a
simplification of rather complex subject, especially for goldsmiths.

Consider the following:

If I take 2 round links put them side by side and solder them. It
will be brazing, because there is no capillary action taking place
and solder simply acts as filler.

If I take the same links, but file a small flat facet on each, and if
facet on one link matches the facet on another, and if I tie these
links together to apply some pressure - it will be soldering, because
I have created conditions where capillary action does takes place.

Regretfully, most of the soldering in actual practice, is brazing,
but when this argument started, I was very explicit in qualifying
what laser welds should be compared to.

I am not going to point finger at someone, who due to economic
realities, defaults to brazing rather then soldering. But it does not
mean that I have to accept statements like

“lasers can do what goldsmiths can’t”

Leonid Surpin
www.studioarete.com


#13
Unlike soft soldering with lead, brazing with a filling material
and tack welding silver solders form eutectic bonds when they are
done correctly. That is to say that the silver/copper solder
diffuses into the silver on either side of the joint as well as
filling the minute gap. As the heat continues the copper molecules
(and zinc if there are any) migrate so that there is a gradient
from the sterling/fine silver to the solder join and back again to
the main material. 

A couple of points, first your use of the term “eutectic bonds” is
incorrect. A eutectic alloy is one that melts at a specific point
and not over a range as most alloys do it is not a descriptor of a
bond type although it can refer to a very specific solder alloy.
Jewelers and craft metal workers are the only ones who still refer to
brazing as soldering or hard soldering or silver soldering etc. The
accepted definition of soldering or soft soldering has to do with
melting temperature. Joining metals (or even ceramics or glasses)
with a liquid filler alloy that melts at a temperature below the
melting point of the base metals being joined and is at or below 850
F is considered soldering, above that temperature it is brazing. If
the melting point is at or equal to the base metals being joined it
is welding.

It used to be stated that soldering did not involve a metallurgical
bond but was rather a mechanical bond and that brazing produced a
metallurgical bond where there was diffusion of the filler metal
into the matrix of the metal(s) being bonded but this is not the
case. The diffusion is present in both soldering and brazing. The
amount of diffusion has to do with a variety of factors including
mutual solubility of the metals involved in both the filler metal and
the metals being joined, temperatures, duration of exposure to the
liquid etc…

It's this graduated join that gives the strength to the silver
soldered joint - and weakens the structure of silver in a lead
based joint. 

No it is that lead and silver just do not form a strong ductile
alloy and copper and silver do.

James Binnion
James Binnion Metal Arts


#14
The author of the above quote is Erhard Brepohl, and the work is
The Theory and Practice of Goldsmithing, page 294, ISBN 0 9615984 9
2. Different printing may have different page number. 

Brephol’s work is great, and I believe it should be required reading
but he is not a metallurgist and he is writing for the layman. His
description is good up to the point where he says that the joint
becomes fully homogenized after several heatings and cannot be
detected even with magnification. This is false, with proper sample
preparation (polishing and etching) and using a good optical
microscope you most certainly can see any soldered joint.

You just don't seem to be able admit that you are wrong about this
topic. 
You are arguing not with me, but with Brepohl and thousands upon
thousands of goldsmiths before him. I am just a messenger. Brepohl
text has been published for many years and in many languages, and
probably the most researched, tested, and proven text on the
planet Earth. 

No I am arguing with you, I seriously doubt Brephol would make such
a ludicrous claim. “The Theory and Practice of Goldsmithing” is a
text book for goldsmiths not scientists and engineers. It is a very
good book but in no way is it the “most researched, tested, and
proven text on the planet Earth” that is pure BS.

You can see practical demonstration of how such joints are done on
my DVD. Here is the link
http://www.studioarete.com/eternityring.html 

Gotta get that plug in for your DVD sales.

Leonid, I have no doubt of your abilities as a goldsmith, you are
obviously quite skilled but your understanding of the science behind
it is not at the same level.

James Binnion
James Binnion Metal Arts


#15

Hi Leonid,

I think this is one where most of us are just going to have to agree
to disagree.

You can make whatever distinctions you like based on joint
structure,

but unfortunately, in English, the actual distinction between
brazing and soldering is based on the temperature at which the
joining takes place. Period. Having your own definitions doesn’t
change what the word really means. Jewelers say soldering when they
really mean brazing. It’s just how the trade language has developed.
The fact that we all know what we mean doesn’t make it less wrong.

As far as Brepohl goes, he’s right, but he’s not talking about
capillary action at the scale you’re using. He’s talking about
capillary action drawing the solder into incredibly minute fissures
in the metal structure itself. Fissures on the scale of a couple of
microns across. (thousandths of a millimeter.) Compared to those,
even the tightest jewelry joint is like the grand canyon. The sort
of capillary action that Brepohl’s talking about simply doesn’t
apply at the scale you’ve been using.

Keep in mind that Brepohl wrote originally in German. The English
edition was translated by Charles Lewton-Brain, who speaks American
Jeweler’s English. So of course it reads as “solder”, but he’s using
’solder’ in the goldsmithing sense. It really should be brazing. If
you ask Charles I suspect he’d agree. I also suspect that Charles
translated it to soldering just to avoid confusion. My German copy’s
in a crate somewhere, so I can’t refer to it directly, but I strongly
suspect that in the German text, it’s “Loten”, which means “Braze”.

That’s not the sort of imprecision that Brepohl would normally
tolerate. Charles, if you’re reading this, please do chime in. I know
you’ve got a German edition ready to hand.

Regards,
Brian.


#16
Obviously they both fill the joint and they both adhere in some
fashion to the base metals. So exactly how do they differ in their
action? 

The key is capillary action. You would be correct to observe that
capillary action is taking place in both cases, but the difference is
in the degree.

Solder is inferior metal from the point of view of structural
engineer. Previously, I mentioned Brepohl. Brepohl also gives very
good introduction to properties of precious metals. Did you ever
wonder why are we using 18k and not 17.5k or 18.5. Not to make thing
overly complex, but if one alloys gold, silver and copper, there are
only 3 combinations which have good mechanical properties and they
are 18k, 14k, and 9k. Slight variations makes a lot of difference in
mechanical properties.

When gap is nonexistent, the solder is drawn inside the joint and
subsequently inside the grain of the alloy, by capillary action and
becomes an integral part of the joint. The whole area around joint
becomes a new alloy.

If there is a gap, capillary action does not take place or take
place to an insignificant amount.

The formula is somewhat unfriendly, so let’s look at it this way. The
formula is a fraction. The numerator consist of surface tension,
angle of contact, and some modifiers, none of which is under our
control.

The denominator is comprised of density, gravitational constant and
radius. Density is inherent property of precious alloy and not under
our control.

Gravitational constant is under God’s purview, but we can do
something about radius.

We can think of radius as the gap between joint walls. Since the
value of any fraction increases by decreasing the denominator, and we
can decrease denominator by making gap smaller; by making gap smaller
we increasing value of the fraction and thereby the strength of
capillary action.

If capillary action does not take place, we simply fill the gap
between joint surfaces with solder, which has inferior mechanical
properties compared to original alloy. Is it any wonder that such
joint breaks under mechanical stress.

Nowadays, refiners trying to come up with formulas which capable of
good mechanical strength and capable of capillary action (controlling
things like surface tension) with varying degrees of success. But the
best results are still produced by perfectly fitted joint.

About term brazing. Silversmiths, most of the time, cannot fit
joints to required precision for capillary action to take place. It
is not a putdown. As size of joint increases, the level of difficulty
of obtaining good fit grows exponentially, so silversmiths solder by
heating joint with torch and simultaneously supplying solder from the
rod, known as brazing rod and technique called brazing.

What about mechanical strength you may ask? Different schools of
silversmithing handle it differently. English formulated their solder
with understanding that there will not be any capillary action, so
formula was designed to increase strength. French increased purity of
their silverware. Hallmarked french silverware is not 92.5 percent
silver, but 95. Some German guilds used 80/20 and employed gilding,
and etc.

Soldering is an exceptionally complex subject with a lot of gremlins
hiding underneath apparent simplicity. It is not uncommon for a
complex piece contain dozens of soldered joints of different types.
And the fate of the piece, whether or not it is going to make
through the final assembly, is depended on a goldsmith deciding which
type of a joint to use.

Leonid Surpin
www.studioarete.com


#17
Can you please explain what is the "quite different role" that
solder plays and how is it different than the role which brazing
alloys play? 

Marty - and all. It’s not an argument, and it’s not a controversy,
Leonid is simply wrong and what he’s actually trying to do is justify
a prejudice against lasers, which is how it all began. Precious metal
"soldering" IS brazing, we simply call it soldering from tradition.
Gold and silver “solders” are brazing alloys, we just call them
solder by tradition. It’s really just that simple.


#18

HI Leonid,

[snip]

Solder is inferior metal from the point of view of structural
engineer. Previously, I mentioned Brepohl. Brepohl also gives very
good introduction to properties of precious metals. Did you ever
wonder why are we using 18k and not 17.5k or 18.5. Not to make
thing overly complex, but if one alloys gold, silver and copper,
there are only 3 combinations which have good mechanical properties
and they are 18k, 14k, and 9k. Slight variations makes a lot of
difference in mechanical properties. 

Nope. Sorry. We use (normally) even karats by convention, habit, and
in many places, law.

Originally, the even karats were what goldsmiths used because they
were the easy alloys to make. 18K is 18/24 (or 3/4) gold, so it was
easy to do the math. Equally so with 22, 14, 12 and 9K. Keeping in
mind that the 24K system goes back to the middle ages, when most
goldsmiths couldn’t read, let alone do figures. Also keeping in mind
that the simple concept of arabic numerals didn’t come into wide use
in the west until the 1200’s. Just try working out the math for a
complex alloy using only roman numerals. (Roman numerals have no
concept of decimal places or “zero”, for example…)

Since the karat alloys you mention predate such simple concepts as
arabic numbers, what’s the likelihood that they were chosen due to
any systematic search for ideal mechanical properties? None. They
were chosen because they were easy to make.

Now they’ve become codified in law in most places. In the UK, you
can (if you want) use 14.5K, or any other silly number you want, but
it’ll still hallmark as the next lower karat, so there’s no
financial point in it. Since it’d just be a waste of money, the
refiners only produce metals that work out to the legally required
fineness.

By way of example, there is an alternate silver standard in the UK:
Britannia Silver. Instead of 925/1000 Ag, it’s 958.3/1000 Ag. It was
used (briefly) during the reign of Queen Anne, and has been retained
ever since. The way they got that particular percentage was 958.3 was
what resulted when the silversmith melted an ounce of fine silver,
and then threw in a certain number of grains of copper per ounce. The
sterling standard at.925 resulted from a similar formulation. Both of
those alloys were chosen for standardization because they were easy
to make, rather than any other reason.

About term brazing. Silversmiths, most of the time, cannot fit
joints to required precision for capillary action to take place.
It is not a putdown. As size of joint increases, the level of
difficulty of obtaining good fit grows exponentially, so
silversmiths solder by heating joint with torch and simultaneously
supplying solder from the rod, known as brazing rod and technique
called brazing. 

Nope, it’s normally known as “stick feeding”, and is metallurgically
identical to the action of the solder if placed into the joint in
pallions. Namely: brazing.

What about mechanical strength you may ask? Different schools of
silversmithing handle it differently. English formulated their
solder with understanding that there will not be any capillary
action, so formula was designed to increase strength. French
increased purity of their silverware. Hallmarked french silverware
is not 92.5 percent silver, but 95. Some German guilds used 80/20
and employed gilding, and etc. 

Please see above: sterling resulted from easy math. As did 80/20 and
.900 coin silver. The need for a stronger/cheaper alloy than pure
silver was genuine, but the regarding the actual alloy percentages
chosen, those came from easy math.

Regarding our discussions of Brepohl, I emailed Charles Lewton-Brain,
the man who wrote the translation you cited, asking him what term
Brepohl used in the original, and whether or not he’d translated it
as “solder” in the English to save confusion. I also asked both
Charles and a Swiss goldsmith of my acquaintance how German talks
about “soldering” in the goldsmithing sense. The text of Charles’
reply is

below:

Ok, I went to look and read the pages. Essentially he defines it
all as l__ten (soldering), hard and soft. in all cases the
material melts, flows in the seam by capillary action and diffuses
into each side of the join. If the metals being joined melt then
one is welding. He then discusses soft soldering, talks about the
negatives, what it is used for and that the 'aformentioned
diffusion is very limited', so he does consider some diffusion to
occur, but almost not noticiable. 
so, its all soldering in Germany. But that does not mean that it
is all soldering in English, different language, culture,
concepts... And is it a goldsmithing book, so an engineering text
might have a different take on it. 
Essentially the difference appears to be the temperature range at
which it occurs and the degree of diffusion that can occur. 

So. It looks like the confusion starts with the original German,
which doesn’t distinguish between soldering and brazing the way
English does. It just talks about hard and soft soldering, much as
American jewelers always have. (I’m betting we picked up the habit
from immigrant German jewelers.)

You will note that the man who wrote the translation you cited
(kindly) re-examined that section of the original text, and came to
the same conclusion as the rest of us: in English, the distinction
has to do with temperature.

As far as diffusion (and capillary action) goes, Brepohl’s talking
about it happening on an inter-crystalline scale, which is vastly
smaller than any joint you or I could make. Thousandths of a
millimeter or less. At that scale, it’s not just silversmiths who
can’t make a tight joint. No human could.

As long as we’re on the subject of books, might I recommend to you
Mark Grimwade’s “Introduction to Precious Metals” (2nd edition). It’s
an entire book devoted to the metallurgy of the precious metals,
written by one of the foremost precious metal metallurgists of our
generation. It was recently rewritten and re-released with loads of
fascinating about not only karat gold alloys, but also
brazing alloys. For example, (from page 166)

"It is important to draw a distinction between the terms soft
soldering, hard soldering and brazing. By convention, soft
soldering refers to joining by soldering at temperatures below
450CB9Ac, whereas hard soldering is soldering above that
temperature. The dividing line is somewhat arbitrary and it
arises from the fact that soft solder alloys have relatively low
melting ranges and hard solders have much higher melting
temperatures. "..."Hard soldering at higher temperatures,
typically above 600CB9Ac, is known also in the engineering
industry as brazing and, hence, these alloys may be known as
brazing alloys because the original alloys were based on
copper-zinc. (brass.) The principles of soldering and brazing are
the same and because jewelers have traditionally used the term
soldering instead of hard soldering or brazing, this will be
followed throughout this chapter where applicable." 

He then goes on to list several pages of fascinating information
about joint design and the metallurgical behavior of hard solders. I
recommend it to your attention.

Regards,
Brian.


#19
It used to be stated that soldering did not involve a
metallurgical bond but was rather a mechanical bond 

When was that? I thought solder bonding was known as a
diffusion/alloying process since microscopes were invented.

Al Balmer
Sun City, AZ


#20

This debate of science vs goldsmithing, and how reliable Brepohl text
is can go on forever. I want to stay on point. The study used to
rekindle this discussion describes cold soldered joint. Even if you
do not accept difference between soldering and brazing, you should
see that.

So on one hand we have almighty scientists, who with all the
equipment available to them, can only manage cold soldered joints,
which any goldsmith with minimal training knows how to avoid. So, to
borrow expression from lawyers " the thing speaks for itself "

About plugging my DVD. Plugging is not the term I choose to
characterize it. The DVD is of very high quality and everybody would
benefit greatly by enhancing their libraries with it. But more to
the point, I am demonstrating different types soldering as conditions
demand. It is very much on the subject, and very illustrative of the
differences between soldering and brazing, and capability of
soldered joint versus brazed one.

Leonid Surpin
www.studioarete.com