String Breakage (Reply)

[Richard Snelson]

I think it work hardens because when its bent you are exceeding the
elastic limit of the metal. (Bending it beyond where it will return to
its orginal shape.) This compounds as you continue to bend as in trying
to break a coat hangar. You are correct temperature is not a factor in
this condition.  



Ron Nossaman wrote:
> 
> At 10:36 AM 1/20/99 -0500, you wrote:
> >OK, Ron, I have a friend who is a metallurgist.  I will ask him what
> >happens re:
> >
> >metal fatigue
> >annealing
> >work hardening
> >
> >and I will get back to you.
> >
> >            Newton
> 
> My Tool Engineers Handbook (ain't estate sales great?) indicates an
> annealing temperature for (generically) high carbon steel at 1400-1450 F. I
> don't have specific temps for music wire, but it's in a similar range. Tool
> Steel Simplified says to cool slowly in the furnace after heating to anneal.
> Hardening with heat requires 100 degrees, or so, higher temperatures and
> more rapid cooling, usually by quenching. Tempering is a sort of controlled
> partial annealing from maximum hardness. Bending doesn't heat the wire
> nearly enough to either anneal, heat harden or temper it. It does, however
> work harden. I would like a good explanation of why metals work harden, if
> you'll ask your friend about that while you're at it.
> 
> Thanks,
>  Ron