heat coloring steel (intentionally)

Hey all,
I'm making some pendants and various other jewelry type stuff for a couple metalworking types I know, they will have a very "machine-like" look to
them. I intend to fasten the parts of the jewelry together with shop-made 2-56 & 0-80 bolts, as part of the decoration. I'd like to heat color them, like clockmakers do occasionally.
Does anyone know how well the color will hold up to wear? Like if it were carried in your pocket w/ keys & stuff all the time?
What exactly *is* the colored stuff? An oxide? I seem to remember that it provides some small degree of corrosion resistance. True?
Do any types of steel tend to heat color better than others? I will probably use 316L, cause I have so much of it, and I'm proud to say, I'm getting kinda good at machining it (I don't swear *every* time I cut it anymore ;-) ) Although I may just go get some plain ol steel if the corrosion resistance warrants it.
Thanks,
Gene
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If you are talking about the bright blue color seen on clock springs, screws, hands, etc., it is called temper bluing. It is accomplished by heating the clean and polished parts to about 600 F either in air or in a molten salts bath. The color is actually a microscopically thin layer of iron oxide and it is not durable. While it does provide a small degree of rust resistance, It is not suitable for pocket carried hardware as it will wear away quickly. It doesn't work on anything but carbon steel, so stainless is out of the question.
Randy

probably
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couple
shop-made
them,
were
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<snip>

Somewhat along the lines of heating metal for the colors, I'm wondering about brushing the almost red hot metal with a brass brush?.. I know it gives a nice looking patina, but anyone know how good it lasts/wears? Thanks..
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Temper bluing is just heating the metal in an oxidizing environment until it takes on the color desired. The oxide film is very thin and translucent. Higher heat causes the film to grow thicker, darkening the color toward the blue range at which continued heating makes the film thick and opaque black, as in mill scale.
The color is caused by constructive/destructive reflection between the surface of the oxide and the surface of the metal underneath. That's why the metal surface must be highly polished to obtain bright color. It is the same effect as the colors seen with an oil film on water except the color range is limited. Temper bluing is well known and predictable with iron or carbon steel and has been used by clock/instrument makers and gunsmiths for at least 500 years, mainly for decoration.
While SS will color with heat(as will chrome plate), I suspect it takes higher temps than carbon steel. I have never seem any data published on temper bluing SS, so I don't know if the full range of colors is obtainable.
Randy

to
getting
anymore
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Heating in air will give you various colors of oxide coating depending on the temperature and alloy, but they will not be durable or rust resistant. Google 'case hardening` or 'color case hardening` for an interesting alternative process. It involves heating the parts in a crucible with charcoal and salts and is a little too involved for a short post here. There is not much color control and the patterns are random but they can be quite interesting and might fit the look you have in mind. You can see the effect on the receivers of some older firearms.
Pragmatist - "Where is Madame DeFarge now, when we really need her?"
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pragmatist wrote:

Guy Lautard's Second Bedside Reader had a good explaination of the process, in the story at the back called "The Bullseye Mixture".
Ken Grunke SW Wisconsin http://www.token.crwoodturner.com / Member, Coulee Region Woodturners AAW chapter http://www.crwoodturner.com /
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