On Fri, 2 Jul 2004 18:09:16 -0500, "Paul K. Dickman"
wrote:

In order to illustrate the nature of the porosity in melted copper I put a
few
pictures up.

http://tinyurl.com/3cw7p

The first labeled Casting is a small ingot cast of ca110 copper It started
out
essentially 99.9% fine. The casting method was about as simple as you can
get.
It was melted with an oxy-acetylene torch and poured into an open mold, made
by
scraping a depression into some foundry sand.

The "cocks comb" sticking out in the upper left is not a sprue. When the
pour
was finished the ingot was shaped like a little loaf. As it solidified,
dissolved gasses came out of solution with the metal. As they did they were
trapped by the solidified metal on the outside of the ingot and built up
pressure. Eventually a weaker spot in the surface of the metal gave way and
metal and gas squirted out. Like stepping on a ketchup packet in the
McDonalds
parking lot.

The size of this is indicative of how much gas was dissolved in the metal.
It is
approximately 10% of the original volume of the ingot.


Measured at what temperature and pressure?


The rough area in the lower left is not indicative of porosity, It is where
the
metal first struck the sand. When it did, it's surface tension was
sufficiently
disturbed to allow it to flow into the spaces between the sand grains.

The second picture, labeled section, shows what this looked in a cross
section
cut at about the base of the "cocks comb"
You can easily see the large bubbles. It also has a large amount of small
bubbles that are visible under a 10 power loupe.
You can see that it looks very similar to the R666 radiograph. However that
piece looks more like a mistake than a deliberate casting.
You can also see that it is not a single round bubble but a miriad of
amorphous
blobs.

The third picture, labeled forgings, shows it's workability.
The lower shot is from the pure copper ingot, You can see it is full of
fractures and tears.
The upper forging is made from an ingot cast from approx. 4% silver-96%
copper.
This ingot exhibited no cocks comb and the forging was made from the entire
ingot, with no waste removed.

The two metals are visually identical, but one casts like crap and the other
doesn't.

If they were casting on any scale, it is not just inevitable that alloying
occurs, it is pretty much a necessity.

If you want to prove casting, stop stroking around with radiographs and look
for alloying.

Paul K. Dickman










Eric Stevens