Quinlin so is not possible to harden Copper by heating it and letting it cool?
I thought I had read some where that heating it up and letting it cool slowly would harden it and if you wanted to soften it you needed it to cool fast, as in Quench it? I must read up on this...
Copper and copper alloys are hardened by mechanical stress (hammering, bending, etc.), and annealed (softened) by heating to relieve that stress. Rate of cooling has no effect.
Carbon steel, on the other hand, will
quench-harden; this is probably what you read about. Steel is iron with a small amount of carbon mixed in, and it is this combination which is responsible for this behaviour — the more carbon the steel contains, the tougher it is and the harder quenching makes it. Low-carbon steel is resilient when annealed and tough when quenched; medium-carbon is tough and becomes hard when quenched (good for cutting softer metals); high-carbon steel is already quite hard, and quenching can make it brittle enough to break when dropped. Cast iron contains even more carbon, and is brittle straight out of the mould, and I seem to recall that pure iron will not quench-harden at all (although I really don't know if I recall this correctly.)
Carbon steel must be brought to red heat, then cooled as quickly as possible to harden. Carbon steel will also work-harden; it can be annealed by being brought to red heat, then cooled as slowly
as possible (eg. buried in sand or wood ash); it can also be annealed or tempered (partially softened) by heating just until the surface oxide layer changes colour (the degree of colour change indicating the degree of softening) and then quenching, which does not cause hardening from lower temperatures.
Short version: carbon steel hardens when quenched from a sufficiently high temperature; copper alloys soften when heated to a sufficiently high temperature and do not harden when quenched.
That's probably far more info than you were looking for, but I hope it's of some use to you.