On Tue, 24 Jan 2006 18:57:10 -0500, "Ed Huntress"
wrote:

"jk" wrote in message
.. .
"Ed Huntress" wrote:

"BottleBob" wrote in message
...

Ahh but the question IS; can tungsten carbide tooling (since it is an
intimate "mixture" of tungsten, carbon, and cobalt), be correctly
referred to as metallic or a metal since the finished product has
metallic properties?

Neither one, Bob. It's a metal-matrix composite. Think about reinforced
epoxy. 'Same thing.
And so essentially is steel, which fairly uniformly is considered a
metal.

The carbon in steel comes in three forms, IIRC, but the one that makes it
steel is not a simple mixture or a compound. It is an incorporation into the
molecular structure of iron -- the crystal structure -- that stresses the
iron crystals. Most hardening mechanisms involve such stress.

Some carbon combines with the iron to form iron carbide. Except for
cementite structures (a phase of steel), this has little to do with steel's
properties. And there can be free carbon in very high-carbon steel, somewhat
like the free carbon in cast iron.

But composite structures, by convention, are ones in which the matrix and
the bound material produce a composite material that shares or combines
properties of the two (or more) materials in a significant way. Free carbon
in steel does not. Neither does the carbide.

Extremely high-alloy HSS, such as CPM Rex 121, actually get some wear
resistance from the precipitated carbides. However, the main one there is
chromium carbide, not iron carbide.

Consider Cast Irons ....

Metals,

http://www.lenntech.com/periodic-chart.htm

metalloids, and "metallics" are defined loosely by their properties.

http://www.shodor.org/unchem/basic/atom/
http://www.sciencebyjones.com/shells.htm

For example, silicon metal is just considered a metal by metallurgists.

A semiconductor ...

But
it has only some of the properties that we associate with metals. Add some
carbon, and it's silicon carbide. Add oxygen, and it's sand.
--
Cliff