"Jack Erbes" wrote in message
...
Meindert Sprang wrote:
snip
Correct. It is a well known physical property of copper. It hardens when
it
is heated.

Meindert

Nope, that's not right. Heating copper (also brass, aluminum, and most
other non-ferrous metals) and cooling it (the quicker the better
generally) anneals it and restores the workability.

You are partly right. Heating a metal above its recrystalization temperature
softens it. For copper, you're talking about at least 480 degrees Celcius.

When copper is heated below this temperature (soldering), the remaining
oygen in the copper can react with hydrogen (possibly released by heating
flux?) causing embittlement of the copper.


That is why reusable copper spark plug washers, head gaskets, etc., are
heated to restored their sealing qualities. They get work hardened in
use and might not seal at a specified clamping force. The sealing
qualities can be restored by annealing.

Yes, but with a soldering iron, you'll never reach that temperature,
generally

Meindert