tempering, was pins and needles

[Ron Nossaman]

>Yep, tempering metal involves heating it to a very high temp, for a defined
>amount of time, depending on the alloy, and then quenching it, either in oil
>or water.
>    When you heat a metal to a high temp, and allow it to air cool, you are
>"annealing" it.
>
>    Now, the question is; does "draw the temper" mean to "draw off the
>temper"?
>
>    My understanding of it is; tempered metals are harder, and more rigid,
>but because of these properties, they are also more brittle.


>From the archived experience of an experienced thermal abuser of things
metallic: ... This.

Working with steels, regardless of the alloy mix and carbon content, mill
stock is normally not hardened. It may be heated and formed, in which case
the starting temper is not an issue, or it may be cold formed, in which
case it had better not be hardened or it isn't likely to be formable -
formable being rolled, stamped, drawn, etc. After forming, steel that will
need to be hard in use is hardened by heating, perhaps adding carbon in the
process to case harden the part, then quenched in water, oil, infidel
thighs, or whatever is appropriate to the process and the historical era.
This is the hardening step. Depending on the ultimate intended use of the
hardened item, it may be too hard and brittle at this point to be safely
usable. This is where tempering comes in. Tempering is a second heating, to
a lesser and more closely controlled degree (sorry) and quenching. The
result is a tougher, less brittle hardness that is more forgiving and
resilient in use. To temper is to moderate. It's somewhere between hardened
and annealed, and is moderately controllable, depending on the material and
methods employed, to any approximate hardness between the extremes defined
by the material.

Actually, the infidel thighs reportedly came into play in the tempering
phase of Damascus steel blade production, rather than the hardening phase,
but It seemed to fit so smoothly there, and was such an attention focuser,
that I left it where it was. I hope you will understand and temper your
judgements accordingly. It's an annealed kind of day.

Ron N