Heat treating for color

If you "heat treat" in a salt bath, you will get a deep blue color uniformly over the piece. If you are talking about various colors, that's called case hardening, not heat treat.

If you try to color case harden an already heat treated blade, it will most likely ruin the temper, though you can do this to fittings without problems, as they are not usually heat treated to begin with.

I have something on case hardening, but can't find it at the moment, and have to leave shortly. If I can find it later, I'll post it here.
 
In general you can color steel by heating it; around 400 degrees gets a yellow "straw" color; up to 600 or so and it starts turning blue. A blade heated to blue most likely wouldn't hold much of an edge. Many people do however heat blue fittings.

These colors are not very hardy though, it wouldn't take much to rub them off.

It'll be interesting to see what Mike has to say about case hardening. The firearms I have with case hardening look pretty cool. Maybe someone has photos of knife furniture treated like that.
 
I can't find the one I want. I sent a copy of that link to Bruce Bump about a year ago, and now can't find the thing. It told how it was done back when, and in pretty good detail too.


I have these two, one by Bruce(?), so it'll have to do for now.
http://www.anvilfire.com/FAQs/case_hardening.htm

http://members.aol.com/illinewek/faqs/case.htm

Incidentally, Dave, the deep blue of the salt bath wouldn't hurt the blade, as it would be the color left from the heat treat process, and the high heat generated. It would still have it's final temper at a lower heat.

As long as one was careful it would stay that deep blue, but like you said, would scratch easily.
 
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