[TheForge] Re: Test mail

[Bruce Freeman]

But wasn't Bealer's reference to "packing an edge" in a discussion of knife edges?  I don't think slag in steel has ever been much of an issue.  Slag in wrought iron is always an issue.  Consistency of steel was very much an issue, and led to the development of crucible steel.

However, if you WERE planning to put a relatively hard edge on a wrought iron implement, then "packing" would make sense both to weld together the edge (at high heat) where slag was a problem, and (at lower heat to even cold) to work harden the edge.  I could see doing this on the edge of a shovel, for instance.  

Bruce
NJ

>>> sos at alum.mit.edu 11/11/2005 8:16:27 AM >>>
 From somewhere I remember that packing might have been important when 
there was lots of slag in the metal, but doesn't do anything with modern 
steels. No reference, sorry.

Steve

Bruce Freeman wrote:

> (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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