Wonderful Alex! The best way to learn about color case hardening is through experimentation (not with customers guns tho, hehe
).
Miller, Carburization is a diffusion controlled process. The longer the action sits in the crucible, the greater the carbon penetration will be and the higher the carbon content. This was taken from one of the machinist manuals out there(mind you it is describing a molten salt bath)
Carbonnitriding starting with low carbon steel (SAE 1008):
1 hour @ 1425 to 1450°F results in a case .004" deep.
2 hours @ 1425 to 1450°F results in a case .006" deep.
3 hours @ 1425 to 1450°F results in a case .009" deep.
4 hours @ 1425 to 1450°F results in a case .011" deep.
1 hour @ 1600 to 1625°F results in a case .015" deep.
2 hours @ 1600 to 1625°F results in a case .021" deep.
3 hours @ 1600 to 1625°F results in a case .026" deep.
4 hours @ 1600 to 1625°F results in a case .030" deep.
For example, compare 1 hour at 1425 to 1 hour at 1600 and youll notice that your steel will absorb much more carbon than if you had run for an hour at 1425. The old low carbon steels that many, if not all manufacturers used to make their actions are essentially non-hardenable. They simply absorb carbon on the surface, leaving a thin "case" to protect the outside, and a soft inner core that allows shock absorption and stresses. A longer "soak" in a carbon-rich environment will yield just as good of hardness (and colors as) if you ran it for a shorter period of time at a higher temp.
