[TheForge] to heat treat or not to heat treat... that is my question.

[Jason Nass]

It's all treated and double tempered at 500... the only mishap being my
butterfingers when pouring the oil into my bucket which lead to a faceful of
used icky motor oil and a mess on the shop floor.

Jason Nass - MacTalis Ironworks
me at wargoth.com

-----Original Message-----
From: theforge-bounces at mailman.qth.net
[mailto:theforge-bounces at mailman.qth.net] On Behalf Of Andrew Vida
Sent: Friday, October 29, 2010 11:00 AM
To: Blacksmithing List Sponsored by ABANA
Subject: Re: [TheForge] to heat treat or not to heat treat... that is my
question.



David E. Smucker wrote:
> Andy,  I wouldn't go all the way "down to Rc 35" which is a draw 
> temperature of about 1000 F.  Instead I would temper at 500 F which 
> should give a Rc in the high 40's, and yield greater than 200,000 psi.  
> Now in using the small end of the bick you might get it to 800 or 900 
> F which would give you your Rc 35 or so and the steel is down to a 
> yield of 170,000. YMMV and experience may teach you that 500 is too low a
tempering temperature.

This is not unreasonable.  I was going for max. tough, but a harder face is
also good.  Besides, the toughness of 4140 doesn't begin to drop off
precipitously until the low 50s as I recall.  But it DOES drop rather
suddenly at some point, which is why I figured 35 would be good.
> 
> For my money 4140 and 4340 are two of the very best engineering steels. 

	Absolutely agree.

	It is wickedly tough stuff - has a very gummy, tenacious quality,
which is a primary reason it is used for gun barrels.  They fail quite
gracefully, given the nature of the failures. I've seen barrels that have
split from muzzle to within perhaps 5 inches of the throat. 
Usually 4 perfectly symmetrically peeled back sections.  Reminds one of a
bugs bunny cartoon when Elmer Fudd's gun blows up in his face - or three
stooges when Moe hits Curly in the head with an ax and the blade splits in
two.
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