charcoal pack case hardening, no colors

[rich pierce]

Let's say someone packed and cooked mild steel in charcoal as if seeking colors, but did not quench the whole batch.  If the parts were later heated and quenched would the hardening be good?

[Ben I. Voss]

Never tried it, but I can't think of a reason it wouldn't work. Someone should try it!

[Jerry V Lape]

I think that if the second heating is not done in a carbon rich environment you will be burning off the carbon gained in the first cooking and the hardening will not be near as good as if you had quenched it the first time around. 

[rich pierce]

Just thinking for small parts (screws, triggers, pins, and lock internals) it might be less messy and dangerous than pouring the whole can full of fire into a quench.

[mattdog]

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"Let's say someone packed and cooked mild steel in charcoal as if seeking colors, but did not quench the whole batch.  If the parts were later heated and quenched would the hardening be good?"


What you are describing is eactly what some manufacturers are doing.  They infuse carbon into parts, particularly frizzens, in a carbon rich emvironment but don't harden them at that time.  This way the parts can still be cleaned and polished, drilled, ground etc. then hardened at a later time by conventional heat and quench method.  

[smart dog]

Hi Rich,
That might work as long as the carbon skin does not burn off during the second heating.  However, one of the benefits of pack hardening is that if the whole pack is dumped in the quench as a unit, the parts are not directly exposed to air, which  produces scaling.  When you heat the unhardened parts in the open air for the second hardening, you will likely burn them and produce scale.  That may or may not be a problem for you.   

dave

[greybeard]

I have read that if you have a casehardened part that you have to rework that you can anneal it and reharden it. That was in the Machinests Bedside Reader.     
No proof as I have never done it . Would have to be pretty deep case me thinks.
Bob

[JCKelly]

To be a picky metallurgist, it can actually be beneficial to cool the parts, then re-heat and quench.
As a rule of thumb, when reheating it takes about 5 minutes at heat to burn out enough of the surface carbon to be a problem.

Me, I'd just dump the whole contents of the pack into water, holding the pack near the water to minimize exposure to air. If you don't like the mess, well . . .

In the early 1970's I recall a video promoting the advantages of vacuum carburizing. The advantage they were promoting was Kindness to the Heat Treater.
Showed the heat treater at Smith & Wesson dumping a pack full of carbon, hammers & triggers into the water quench. Messy, messy, messy. But (at that time) S&W did make good stuff.

[Dphariss]

Let's say someone packed and cooked mild steel in charcoal as if seeking colors, but did not quench the whole batch.  If the parts were later heated and quenched would the hardening be good?

If I did not want colors and was doing small parts  I would use Kasenite.

Dan