[TheForge] Re: Test mail

[Bruce Freeman]

(I should have read both these postings before responding.)

Yes, hammering springs may harden them.  I am not a metalurgist, so I won't try to explain why that works.  I can give a lable for it, "work hardening", but that is not an explanation.

However, I AM a chemist and have taken the usual courses in physics.  NO WAY you can compress atoms or even metal grains (tiny crystals within a solid metal) with a hammer.

>From the small amount of metallurgical reading I have done, I believe I recall correctly that you CAN break, distort or otherwise stress metal grains with a hammer.  Annealing is the process of removing such stresses by application of heat (and, for steel, by slow cooling - - which is not necessary for pure iron or other metals).  Anyway, it seems that these small, distorted crystals are HARD.  Hence, hammering leads to hardness.  (I defer to correction in this interpretation to any metalurgist lurking.)

Steel is different in that the carbon content radically changes its properties relative to the pure iron metal.  Tiny crystals can arise in steel by heating and quenching.  Since these tiny crystals impart hardness to the metal, a "simple" means of hardening the metal is available.  (This judges work hardening as "not simple" - clearly a judgment call.)  

Hope this helps.

Bruce
NJ

>>> stephen.viola at gmail.com 11/11/2005 2:25:21 AM >>>
I'm not sure about the scientific detail, but I do know that way back
when, the making of springs for buggies and carriages were hammered
hard and not heat treated. So there must be some truth to the
compacting of grain or atoms. Blacksmiths have been doing it for
centuries. At college we are taught that the compression of atoms
occur when hammered. Thats not to say that other material is
displaced, just that there seems to be some kind of allowance for the
metal to become harder with the compression. Like I said I don't know
the scientific blah blah, but thats the understanding I have.

Stephen (Finland)

On 11/11/05, Erik Gutfeldt <erikg at apple.com> wrote:
>
> On Oct 31, 2005, at 4:59 AM, Bruce Freeman wrote:
>
> > I do vaguely remember his discussion about "packing the edge" of a
> > knife.  Pure nonsense.
>
> I thought the metallurgical effect of "packing" was to reduce grain
> size.
>
> Erik
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