Copper Casting In America (Trevelyan)

Bwaa haa haaa haa.

I should check in on threads like this more often. A little bit of howling funnies is good now and again.

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

I didn't say it wasn't welding, I said it wasn't brazing.

Horse hockey.

Here's a quote from;

The sword was one of the main areas of decorative metalwork in feudal Japan. Some of the finest and most skillfully wrought metalwork in the world was used in the creation and outfitting of many of these swords. The innovation of this decorative technique is attributed to Denbei Shoami (1651-1728) a master smith from Akita prefecture. Shoami?s first piece is comprised of layers of copper and shakudo (a Japanese copper alloy that contains 2.5% to 4% pure gold) laminated to create a tsuba (sword guard) that was carved and flattened. The effect is similar to Chinese and Japanese lacquer work known as quiri-bori ?where thick parallel layers of alternating red and black lacquer are built up to a considerable thickness and grooves are deeply incised to expose colored lines on their sides? Shoami gradually learned to flatten and to produce wood-grain patterns that lie on the surface of the laminated mass.

No, brazing requires a filler metal with a melting point below the metals being joined

Again, they are not necessarily pure metals. If they were (pure copper and fine silver) That bonding temperature would be roughly 2/3 the liquidus temp of the silver/copper eutectic.

I look through my notes and found the origin of the term sweats in this context, and I was wrong. I thought it was the crew I worked with as an undergrad grunt at SIU in

Members of the Graduate Program Southern Illinois University Carbondale: Marvin Jensen, Philip Baldwin, Stephen Brunst, Lori vanHouten, William Ard, Janice Nathan, Randy Jones, Prof. L. Brent Kington, Prof. Richard Mawdsley; ?Return to the Forge: Extended Research into Mokume-Gane and Granulation? Society of North American Goldsmiths 1979

but it was the Pijanowskis in

Pijanowski, Hiroko Sato and Pijanowski, Eugene M. ?Lamination of Non- Ferrous Metals by Diffusion: Adaptations of the Traditional Japanese Technique of Mokume-Gane? Goldsmiths Journal August 1977 pg 21

The Pijanowskis used a liquid phase bond that required a melted surface. However after Marv Jensen developed the torque plate clamping, I think that even they went to the lower temp solid state diffusion

So you are saying that native Americans working with stone tools could manage to cast a largely uncastable metal, but the Japanese, who raised metalwork to an artform rarely duplicated, couldn't judge temperatures

As to people familar with making Mokume gane, I added two more photos to

Showing some of the Mokume gane I made during those years.

Paul K. Dickman

Again an infinite number of alloys could be used.

And, unless you are merely bonding copper to copper alloys will be created by the process.

There is NO weld technique which produces a weld with metallurgy identical to the the parent metals. ANY weld technique leads to a discontinuity in material properties in or around the weld zone which ALWAYS results in a propensity for the welded structure to fail in or around the weld zone rather than the parent metal.

They are merely immovably stuck together in such a way that it may require an electron micrscope to detect the interface.

This phenomenon only occurs with precision gauge blocks for the simple reason that their faces are so flat that the atoms of one piece of material brought very close to the atoms of the other. When the interface is broken an electron microscope will show the tears where the asperities of one surface have welded to another before separation.

No sudden impact is required to create such a weld. Neither is heat, friction or any other mechanism to cause melting.

Electron microscopy says you are wrong.

Eric Stevens

Didn't need to as "welding" wasn't involved in that case - "melting" was - from a round flat disk to a crown wheel for a diff.

Not quite - the Mini crown wheel blank was not preheated in any (visible) way at any stage. The process in the URL differs in that molecular friction alone isn't used to heat the blanks to a momentary melting point.

In any event this is wandering off topic at the moment.

I suspect you snipped the wrong text there! What you left isn't mine.

But then explain how come each strand of a multi-strand cable can easily be separated from each other - even if very fine strands? Also electricity uses only the surface of any wire - so it isn't as if it holds the wire together either. I think you are confusing something with "welding".

Ahhhh..... nothing to do with welding at all. You are barking up the wrong tree - try simple air pressure. Two steel blocks each with a perfectly smooth surface, and you place those surfaces together - you can lift the bottom block solely by lifting the top one (momentarily at least). Air pressure, is what is holding them together. I have a set of dies made for me by a tool-maker mate that I can demonstrate exactly that with.

Not knowing what a "slip-gauge" was, I looked it up and they tell the same story.

"The measuring faces of Slip Gauges have such a good surface finish that when you place two gauges together with their measuring faces in contact, and slide one gauge over the other, they will wring together. Basically this means that they are almost stuck together, and that they will not slide off each other easily."

Nothing at all to do with welding.

Yes I understood as much.

I can understand that during a melting process where molecules are at their most active, some reaction to air and a certain amount of mixing can occur. What I find difficult is that an annealing process causes bubbles -UNLESS it is overheated to a melting point locally. How else does something get INTO the metal to cause bubbles when it is pure to begin with?

Indeed, and that is because it has no inherent flaws with in it, to cause fracture points. Only it would appear, as I read various replies, than in certain circumstances "welding/forging" etc occurs without much temperature - Eric is even suggesting room temperature in one reply. Only when copper has been melted and has these gas bubbles occur, it can't be done - apparently.

I do understand the idea of oxidization, but that would result in embedded impurities more than wholly prevent welding to occur. Granted it wouldn't be as good a copper as modern melting techniques provides, but then such techniques and quality wasn't known about then and ignorance is bliss. They would have been happy with what they could do.

So it would appear that implied in the last statement is - the more frequent annealing the better the outcome (for shape). Of course, in this case you haven't trimmed the piece which might have been done in that sort of situation of a severe crack by the ancients.

That one I'm also familiar with - and it doesn't only apply to forging :-)

It is something I have been thinking as well.

Arrow and spear point are relatively small, and would want to be of a medium hardness only - so the tips of retrieved arrows/spears would be beneficial to NOT be too hard - so they will not break when missing the target - and so they can be restored again when bent.

Certainly in Mexico casting was used even for very small items.

[..]

Exactly :-)

But I was discussing welding. You seem to be confusing cold forging with welding.

Sorry. There is no melting in either hot or cold forging.

I'll say.

the role of dislocations in metal deformation. Forging is possible as a result of the mobility of dislocations. All that heating a billet does is increase their mobility. It is not necessary to cause melting unless of course one is trying to undertake casting.

Eric Stevens

Hmm.

"The billets, composed of various combinations of gold, silver and copper alloys ....

No.

A eutectic can a,d soes apply in some cases, at the interface. Copper will do this with gold, silver, aluminium and zinc, and no doubt a few other metals besides.

Eric Stevens

At high temperatures oxygen is soluble in copper.

Eric Stevens

The point is that they have not been forced together under pressure.

You are thinking of the 'skin effect' which applies to high frequencies. You can ignore it for DC of ordinary AC.

I bet they weren'r of grade 0 or 00 quality. If they were, you wouldn't want to leave them together overnight.

Eric Stevens

Atmospheric oxygen actually dissolves in molten copper, much as CO2 is dissolved in a soft drink. Take a common Coke, put it in the freezer, come back in 30 minutes and pop the top. You get a foamy mess. The same thing happens when molten copper freezes. The oxygen tries to common back out of solution, causing the foamy mess copper workers call characteristic porosity.

How about when the native copper was formed? Masses of native copper typically have small inclusions, bits of rock, silver, etc. In particular, in the Keewenaw range, calcium carbonate inclusions are common (refer back to the frequently referenced article giving the geology of the region).

When calcium carbonate is heated, it decomposes into CO2 and calcium oxide fume. The CO2 will blow a blister if the inclusion is near the surface of the piece of heated native copper being annealed.

You have to understand that native copper is chemically pure (99+%) metallic copper by definition, but it is deposited in a rock matrix where it is later found and mined. Small inclusions are common. They aren't *chemically* combined with the copper, the copper is still pure, but they are *mechanically* combined with it.

Gary

Simply over annealing one time should not cause bubbles where no flaw existed. However, over annealing can play havoc with the grain size, subsequent forging can start and then enlarge a separation caused either the weakened grain structure or possibly a preexisting flaw. If gas or moisture is able to permeate this separation, heating will will cause that gas to expand, forming a blister.

The piece in question was the blade that had one single blister clearly visible on the surface as well as in the radiograph. If this piece were able to be radiographed from the side, I would bet that the blister would be lentil shaped, showing clearily that it was caused by the expansion of what had been a flat flaw.

This is not to say that the piece could not have been melted and the flaw flattened by forging, but it also doesn't conclusively prove that it was cast.

Yes, with a lot of annealing you can coax a lot out of even bad metal. but the closer the anneal is to the finished product, the softer the finished product would be.

Even at it's hardest, copper is pretty darn soft.

I have no idea of what purity of copper they were using. Native copper essentialy is crystalized out of a superheated and supersaturated geothermal stew. The longer it takes this stew to cool the bigger and purer the crystals are. The native copper in the UP tends to be of abnormaly high purity. This is were the casting problems come from. Were they to melt a piece of half breed with sufficient silver, there would be few problems casting it.

Paul K. Dickman

I refer you to your words: "forge welding" that I replied to.

I have no problem with any of the above being accurate. However I return to *my* words in reply to Gary talking about silver inclusions in copper artefacts where he claimed: "The presence of silver inclusions *proves* the native copper was not melted after being deposited." the "after being deposited" is read as being done by nature, I point, among other things, to other uses being possible:

"Further more IIRC there is a method of laminating copper and silver sheet and carving through one into the other. .... So silver in copper can also be deliberate - as decoration." (Note, "in" being a typo, should read "on")

Therefor there is no reference to an alloy at all - but later (when I remembered what it was called) it was a reference to a particular process, a process that isn't limited to any particular metals, alloyed or otherwise.

Fair enough you are right of course - only that it may well be the silver sheet can be considered to be "a filler" (the lower melting point metal of the two).

[..]

Indeed, only that it is what I was speaking about.

I can't see silver "sweating" at a lower temp than melting point. I don't see the logic for your claim when we are not talking about an alloy but two dissimilar and independent metals. Merely the fact of them being adjoining should have no effect on the individual melting temperatures.

Oh, and here I thought that a "Return to the Forge" would indeed result in sweating :-)

It is this process the "sweating" would refer to, I expect

Well... there is another instance were a misleading and inappropriate term is used again -"diffusion"- .... I don't think so!

DIFFUSION - noun [mass noun] the spreading of something more widely.... Anthropology: the dissemination of elements of culture to another region or people...... OED.

Why on earth not use the term "bond" or "fuse" meaning to join or blend to form a single entity or "fusion" meaning, the process or result of joining two or more things together to form a single entity?

A metal that WAS being cast in North America in pre-Columbian times, you mean - the evidence isn't available to say conclusively either way for the Michigan Copper specifically.

Don't sell people short just because they used stone tools - they achieved far far more with them than we could ever do.

In fact I said exactly the opposite - that they COULD judge temperature and described the method as "when the silver starts to sweat".

I saw those and wondered about the items...... excellent work!

Still I wonder why a wood grain effect was sought after when actual wood is (A) much cheaper (B) even more decorative.

Here is how to do it:

[..]

No, it appears that there is an issue of splitting hairs into quarters again. At what point is something "melted"? It appears that it has to also need the "melted" + "a length of time" to qualify as such.

So if you want to go pick up one of those crown wheels, with your bare hands immediately AFTER it is made - the same piece of metal you put into the die BEFORE the event with your bare hand - well go for it, you say it is "cold" after all!

[..]

So you say the copper has to be melted at that point, as you claim "soluble" - in a SOLUTION! As I thought...

.... or even more than one time "where no flaw existed"....

Yep, that is quite possible too - only then one would expect, under close inspection, it would show a crack to the outside. Still one more thing is required - the metal be hot enough to be quite "plastic" for it to expand and form the bubble. Which isn't a long way away from it being fully melted to a liquid form

As you have demonstrated the bubble's shape isn't a governing factor of its cause.

The problem being two fold. One the radiographed picture showing the bubble isn't large enough to see if it has any associated porosity with it. Again forging can have reduced the visibility of such as well as any telltale shape of the bubble. The only other "clue" is the text claiming "proof" of "cast". Until proven to the contrary, one would have to assume they had a better view of the radiograph and physical inspection of the artefact than we have from the web page - secondly that they have the knowledge of the effect of casting - as well as forging of cast billets.

I for one am not prepared to reject their view on the basis of the information able to be seen on the web page. Instead I would say even IF it is cast, it is insufficient evidence to claim any common practise of casting from those few artefacts without further investigation.

Yes, I though it was probably the case - here it is worth noting that the "bad" is a relative term and to the ancients it probably wasn't as "bad" as it would be to modern craftsmen.

Yep. Here again is information that isn't known or at least readily available.

But they wouldn't know that. What they would note is that the tips would break after having been bent and unbent several times. Sharpness to the point and sides of a projectile tip would probably be more important to them than the hardness.

It was mined in West Mexico, and exported to where it was used.

So I believe. I have no idea of the purity of copper from Mexico, but this is stated:

"Bells of native copper were among the exotic goods excavated in Chihuahua, Mexico ......" As I understand it "native copper" is a reference to rather pure copper.

Thank you that were the words I was looking for those that equals or points to "melted".... and this I have no problem with.

[..]

OH no you don't! You claimed "chemical" remember - not "melted".

...as I have been suggesting - small pieces made bigger via melting....

We were talking about so called "native copper" - ie PURE copper. My pointing to inclusions of all sorts of other imperfections among the "pure copper" veins has been rejected as it tends to point to a necessity of purification via melting. Isn't this argument now supporting my earlier suggestions, previously rejected? You are now the second person to point to "melting" for the bubble to occur/form.

As in so many other areas, your knowledge of metallurgy appears to be unique.

Eric Stevens

Oxygen is soluble in copper at temperatures below its melting point. In much the same way hydrogen is soluble in iron at ambient temperatures. Look up 'hydrogen embrittlement' if you don't believe me.

Eric Stevens