Copper Casting In America (Trevelyan)

Eric Stevens wrote:


[..]
Anything can be welded at virtually any temperature by using pressure. The Mini Minor crown wheel for the diff started off as a steel disc cut off from a round billet. This was placed on a mould at the end of a hydraulic ram, and the other half of the mould was on another hydraulic ram. To form the crown wheel they were slammed together under huge pressure - it made a very nice crown wheel - and fast!
[..]
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wrote:

You are confusing forging with welding.
Eric Stevens
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Eric Stevens wrote:

Actually I referred to neither. I referred to the use of pressure only as "merely by pressure" was your point.
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wrote:

You say it started off as a steel disc. You have not mentioned two pieces which were welded together.
http://www.forging.org/Design/pg6_9.html describes the manufacture of gears using a similar process to that used for the Mini.
Eric Stevens
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Eric Stevens wrote:

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.
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wrote:

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.
http://www.tf.uni-kiel.de/matwis/amat/def_en/kap_5/backbone/r5_1_1.html discusses 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
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Eric Stevens wrote:

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!
[..]
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wrote:

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

[..]
So "unique" that you cannot find a hole in the arguments I put to you, instead you find a need attack me personally not only on this but also "in so many other areas" - your mere assertions amounts to nothing. Remember the last time you resorted to something like this - can I just mention "slide rule" to remind you, hmmm?
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wrote:

The question then was whether 43/7 equalled 18/3. I said it didn't. You insisted it did. I think I abandoned that argument at the point when you effectively resorted to arguing that 'approximately' is identical to 'exactly'.
Apart from that, those forging blanks were NEVER hot enough to melt. It was NOT NECESSARY that they be melted for them to be reformed. One of the reasons for forging is to presever the original grain flow of the lank and that would be lost if the blank was melted.
Eric Stevens
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Eric Stevens wrote:

I can no longer recall the number, and care even less - FACT is that they are close enough to being equal. So in ancient times if they used shit houses as one set of measurements, and yard arms for the other, they are close enough considering no fractions were used - a measurement for which an APPROXIMATE conversions was given - a measurement for which that level of accuracy is more than adequate.
You came unstuck on that one and still are all at sea with it - as your recent argument about a nautical mile and "great circle" circumference measure, which is ANY circle around ANY part of the globe, when the specific circumference given was at the equator - nowhere else. Something that varied sometimes by a few meters - like WOW!!

When ONLY approximates were given then only an approximate can be VALID and can NEVER mean your petty hair splitting "accurate" claimed to be achieved FROM an "approximate" - it can't. Simple as that. You are resorting to the same sort of nonsense game again!!

Prove it!

Prove it! Remember you are talking about a fraction of a second in time as well.

(I have no idea what relevance "long, limp, and straight" (lank) has to anything here so I'll ignore the term.)
Not true for the particular example given - other similar items are cast and machined in the traditional manner. Again you only make totally unsubstantiated assertions and do not speak about the reason WHY at all! You know, that thing that makes it work and proves your claims. Haven't you found it on the net yet?
So let is look at this "grain flow" claim:
This is advertising spoof for a Japanese made Golf club: "Grain Flow Forging exceeds the conventional forging process by repeating the high pressure compression process to ensure a tight uniform grain structure through the clubhead. Each head is forged from one piece ensuring an uninhibited grain flow through the head and neck."
So there of forging and "grain flow forging" - apparently... but - no hammering - hydraulically pressed from a single small billet - ie mass produced by machines where SPEED of production is of prime importance. Another source says:
"Forging refines the grain structure and improves physical properties of the metal. With proper design, the grain flow can be oriented in the direction of principal stresses encountered in actual use. Grain flow is the direction of the pattern that the crystals take during plastic deformation."
So a lot of gobbledegook in reality if compared to your "expert" claim of "preserves the original grain flow" and "cold". Which is a load of nonsense for the example I provided - it isn't important. What IS important is unit speed of production and therefor unit cost of the production. So slam two dies together and form a crown wheel for a Mini in a fraction of a second at tremendous pressures like up to some 50,000 tons and tell me no part of it did melt at any stage! Oh and you call this "cold forging", when the more correct term is "Open-die forging" or "Closed-die forging" or even "Two stage closed-die forging". There is nothing "cold" about it.
Oh and to finish off with the golf club:
"Ageing the head at elevated temperature optimizes strength and softness." Oh well...... so much for the "cold"....
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wrote:
--- snip ----

My apologies. I should have typed
"One of the reasons for forging is to preserve the original grain flow of the blank and that would be lost if the blank was melted."
http://www.efunda.com/processes/metal_processing/Forging.cfm explains it very concisely.

See above

All fairly straightforward.

Nor is there any melting.

700C is elevated but still far below melting.
More than enough of that subject. If you won't learn, then you won't.
Eric Stevens
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Eric Stevens wrote:

Seen it - it doesn't advance your claims at all cnosidering the "grain flow" is not a consideration.

Nothing there - doesn't discuss the process I mentioned.

So why is it that you are totally unable to explain it?

A parrot on a cage can do just as good as that - therefor it is arguable the parrot's knowledge is comparable to yours :-)

You cannot know what they have in mind for "elevated" it is a relative term and all you can relate it to is the melting point. In that case it is far more likely the "elevated" is far greater then 700C!!

Learn what? You have provided nothing to learn from! On the other hand, you are in the process of learning youself. Here is another lesson for you:
"A material exists as a solid when it is below its freezing point." and "Keep in mind that a material's freezing point is the same as its melting point." - Steve Gagnon, Science Education Specialist!
Please don't confuse "solid" with "solution" again.
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The evidence of porosity is available to the naked eye in that thin copper flake. There are dozens of tiny bubbles in evidence, You don't even need a radiograph to see them. A radiograph or a density test would settle the matter absolutely, but neither is really needed here as the sizes and numbers of bubbles already visible are clear indications of atmospheric melting.

The large numbers of tiny pits in that piece are suggestive of porosity, but a stereo radiograph, or a density measurement, would be required to determine if the piece is actually riddled with porosity, or if we're just seeing corrosion pitting of otherwise sound copper (if the object is indeed copper, and not a bronze alloy).

Pre-Columbian, or Spanish Conquest? I don't see a precise dating associated with the individual objects. The web site says the collection of objects date from the Post Classic and Spanish colonial periods. Also, the web site says the objects are a mix of copper, copper-tin bronze, and copper-arsenic bronze. What evidence do you have that the two particular objects you selected from that collection are pure copper rather than bronze?

You're wrong on both counts. Copper is a malleable, ie plastic, material even at room temperature. At annealing temperature (500F or greater) it is much more so. Bubble gum need not be molten for bubbles to be formed in it, neither does copper. And while copper can be welded, in an inert atmosphere, by melting, it can also be welded at lower temperature by pressure.

And wind up with a porous lump of no use to anyone. Really, you haven't absorbed anything anyone has been telling you about the atmospheric casting of pure copper.

That's your interpretation. But since your interpretation is wrong, your conclusion is also wrong.
Gary
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Gary Coffman wrote:

I don't actually SEE any bubbles at all in the pigs, not even when magnified to its largest extent - where 1 cm = 3.5 cm on screen.

Now in this item I can definitely see "holes" that you call "porosity" - and you have difficulty accepting it as cast - despite it clearly displaying the shape a mould. I would even suggest that this metal was well overheated when it was cast from the pure look of it.

The items are pre-Columbian from around 1300 AD. They are described as "Two copper pigs". I accept their view of it being copper.

It is malleable in relation to granite but then so is steel....

Fahrenheit is a long ago discarded temperature measure here and it is fairly meaningless to me - however the 500F appears to be a temperature people use to bake cakes or roast a leg of lamb in a standard domestic oven. I don't even see the copper glowing red from heat at that point. Naturally annealing can be done at almost any temperature, but from other things I have read, much much higher temperatures are in fact used before the term "annealing" is applied to it. Eg go get the metal red hot.
But one thing that does puzzle me in this claim of yours. A piece of pure copper, as a result of bringing it up to baking temperature can cause "bubbles" - forget the baking, take it to dark red state to form "bubbles". From what does the "bubble" form, we are talking about pure copper here? How did (whatever) get INTO the copper to form a bubble in the first place?

Totally irrelevant. But you do point to an external source for the bubbles by that example - so how does it actually get INTO the copper in the first place if it isn't (partially) melted?

No it can't. "Pressure" in itself does almost nothing. A loaded freight train running over a "copper" coin only flattens it and does nothing else. It is the sudden impact pressure that causes the molecules to move rapidly, that causes FRICTION, which in turn causes heat and if sufficient sudden pressure is applied (eg hammer blow to already hot metal) it CAN melt the material. To "weld" something by definition requires bringing part of it to a liquid state - ie melted in the portion being welded.
WELD - verb [with obj.], join together (metal pieces or parts) by heating the surfaces to the point of melting with a blowpipe, electric arc, or other means, and uniting them by pressing, hammering, etc - OED.
Though I note that "metals" isn't the only things welded - plastic is also welded, but the rest applies just the same. It also reminds me of an axle being welded onto the wheel mounting flange. The axle is placed against the flange with pressure, and spun very fast. When suitably hot, the rotation was stopped, added pressure was applied, the axle was pushed in on the flange by about 1 cm, this to weld it. This melted the material in the joint part as well as expanded the contact area.

The evidence exists that casting was used - Eric Stevens has provided expert testament to that effect. I have pointed to actual evidence (such as exists) including in this post. You label cast copper as "of no use to anyone" when it obviously was of use. You are probably very right in everything you say -for today's use when high quality melted copper can he had - but that isn't the issue at all. Frankly, if you find it "useless" in your endeavours is irrelevant, it doesn't mean the ancients did. YOU are not them.

You are very quick at labelling "wrong" without a single shred of proof or alternate theory! I therefor totally reject such unsubstantiated claims as worthless.
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wrote:
---- snip ----

You are wrong, particularly in the case of copper. The power in your house comes to through a large number of cold welds formed merely by pressure. This is true irrespective of whether you are supplied via copper or aluminium cables.

How do you explain the well known welding at ambient temperatures of precision slip-gauges made of hardened steel? Leave them in contact overnight and you will be lucky to get them apart in the morning.
--- snip ---
Eric Stevens
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No. While true cold welding can occur, that's not the mechanism(s) responsible for wringing gage blocks together.
Frankly, the exact details are still in dispute. Part of it is atmospheric pressure differential between the outside and the area where air has been forced out from between the blocks. (up to 14 PSI) Part of it is often due to the stickiness of oil on the blocks. (roughly 2 or 3 PSI)
But neither mechanism is strong enough to account for the amount of force typically needed to separate the blocks. (typically on the order of 100 PSI)
Most experts believe that Van der Waals forces (the same forces that give water surface tension, or make solder adhere) are responsible for the bulk of the effect. Others now point to the Casmir force (a quantum effect). Lively disputes still continue.
A true weld is as strong as the parent materials. (up to 200,000 PSI for tool steel gage blocks) When you break a true weld, parts of the parent materials are ripped out. That doesn't happen when separating wrung gage blocks. So that's not an example of actual welding.
To do an actual weld, the atoms of one piece of material have to be brought as close to the atoms of the other piece of material as the atoms of one of the pieces are to each other. At room temperature this requires a lot of force, on the order of the yield strength of the material.
This is a few thousand PSI for relatively low yield materials like copper, or more than 100,000 PSI for materials like tool steel. Of course, as you increase the temperature, the yield strength of the material declines, and less force is needed. When a material melts, the yield strength goes to virtually zero, so little or no force is required to achieve a weld.
Gary
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inadvertantly omitted:
wrote:

... when he quoted my response to it.

You are discussing the underlying welding mechanism. The point is that, in those circumstances, welding occurs without either heat or significant pressure, irrespective of whether it is due to Van der Waals forces, the Casimer force, atmospheric pressure or whatever. I do know that if such gauges are left in contact for sufficiently long it is virtually impossible to separate them.

That is very rarely the case.

It depends upon how long you leave them together.

So?
But we (Seppo and I) were discussing welds at ambient temperature. See http://www.twi.co.uk/j32k/protected/band_3/ksedn002.html
Eric Stevens
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Actually, there was nothing inadvertent about trimming the message of older quoted material which anyone with a proper threaded newsreader has already seen, and can access again if they care. It is just good netiquette to only quote enough material to show the statements to which one is responding.
Not doing such trimming is poor netiquette, and results in deeply nested reposted material, causing posts to be of excessive length, which are tedious to wade through to find the relevant new material. Some participating in this thread seem prone to do that. It is bad form.
Any nesting of quotes greater than two levels is generally excessive, with rare exceptions. (Complaining about excessive quoting is one of those rare exceptions.)
Now on to the factual dispute.

No, I am not. I'm telling you welding is *not occurring* when gage blocks are wrung. Perhaps I need to use smaller words and shorter sentences when trying to communicate with you.

It may be the case when an incompetent is doing the welding, but any sound weld is as strong as the parent material.

Leave them together until hell freezes over, they still aren't welded.

So, wringing gage blocks doesn't produce forces that even remotely approach the levels necessary for pressure welding to occur. I thought that would be obvious in context, but if you need it spelled out in smaller words, I'll try to oblige.

Indeed, and you used the wringing of gage blocks as an example. It is a faulty example, as I explained.
I didn't bother to "me too" your good example of copper electrical line splices, since such piling on is considered bad netiquette.
The pressure generated by the hydraulic swaging tools used by linemen is sufficient to cold weld clean copper. That was a good example. But your choice of the wringing of tool steel gage blocks as another example of cold welding was not. No welding at all is occurring in the latter case.
Gary
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wrote:

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
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