Addin Carbon

[peter nap]

I had a really busy week and today is my only day off so I decided to play. I wanted to build a bird and trout knife. I also wanted to experiment with some mystery steel I had. It gives a mild carbon fork when spark tested and just plain doesn't get very hard. It will rust but slowely. Anyway...first I made a half dozen knives. I heat quenched one in crisco and it did nothing. ATF, nothing, hot water was a little better and room temp water hardened the most but still not much. I stuck it in a vice and it snapped off so it had done something to it. I tempered it at 300, snap, 325 snap, 350 and I got a little flex......OK

The steel just was not hard enough though so I cheated on the next one.
I filled a pipe with bone meal and buried the blade in it. I brought the whole mess to near welding heat and pulled the blade out, quenched it and file tested it. Rock hard. I ground a few 1000's and soft inside. (I've said before that introducing carbon is just a surface treatment IMHO)

The next one I ground the blade very thin before going through the bone meal routine. This time the blade was thin enough that it went side to side for the first 1/2 inch of blade.

I made another one and did the same thing and tempered it. It is hard enough and I think will work for what it was intended. That was interesting although kind of a shoddy way to build a knife.

 

[Crayola]

That kind of experimentation is fascinating! Thanks for sharing. In the future I would love to spend a day making the "same" knife, but varying the grinds, going real thin, thick, and playing with heat treat. I bet a guy can learn TONS that way.

 

[Bruce Bump]

Peter, Thats what I call a fun day. Where did you get the bone meal? What you are saying is that you can case harden mild or too-low carbon steel by baking inside a closed pipe with bone meal and quenching. What temp? about 1500F? I still have plans to color case harden with charred leather and bone quenched in water. It will make pretty fittings.

 

[peter nap]

You can get bone meal at any good garden center Bruce. I'm not sure what the inside of the pipe was but I expect the outside was closer to 1700. We had a discussion on this a while back where the coal forgers were wondering if carbon was really added. My feeling was that it was just case hardening. I'm not sure what I was trying to do other than see how deep the carbon would bake in. A case hardened knife is not much good but an edge hardened knife would be OK. It does seem that on the very thin cutting edges the steel will get hard all the way through.
I assume the same thing happens with a coal forge. Iff nothing else, it does make a beautiful color.