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

[Andrew Vida]

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.