On Oct 8, 13:36, Jan Koller wrote:
>
> > Anneal - is that where you heat it up & hit it with a hammer? Or do you
> > just heat it up and let it cool again? I forget now... It's been a long
> > long time since I had any metalwork lessons.
>
> Heat to cherry red, then cool very slowly, often covered in lime, IIRC,
> to hold the heat in. The very slow cooling keeps the metal soft, vs
> cooling quickly ( quenching ) to harden.
For mild steel, yes. You need to let it "soak" in the heat for about an
hour per inch of thickness for it to be fully effective, too.
For other metals, the temperatures vary and the slow cooling is usually
unnecessary. In fact, for mumetal (as used for magnetic sheilding) the
typical annealing temperature (to get the best magnetic properties in this
case, rather than greatest malleability) is in the region of 1250 C to 1600
C (cherry red is about 800 C), and it's supposed to be quenched very
rapidly to preserve the fine grain structure. For copper, the annealing
temperature is between 400 C and 750 C depending on impurities and how it
was hardened, and it doesn't make much difference whether it's quenched or
not.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Mon Oct 08 2001 - 15:56:02 BST