Carbon Absorbtion

[Mark Williams]

Could anyone tell me at what temperature pure iron would absorb carbon?

Thanks

[Quenchcrack]

Carburizing is normally carried out in the temperature range of 1500-1750F, depending on the alloy and the desired case depth. Key to getting the carbon going into the iron instead of coming out of the iron (decarburization) is maintaining a high carbon potential around the iron. In commercial applications, it us usually done with a carbon rich atmosphere that is created inside the furnace. Bladesmiths and blacksmiths usually use pack carburinzing. I assume you are using this technique and are familiar with how to do it. Carbon diffuses at the rate of about .006" per hour at 1700F.

[Mark Williams]

What packing media would you suggest Bob? I'm thinking about using coal dust or maybe graphite. Anybody have a box of fullerenes laying around?

[rhrocker]

Quench said: "I assume you are using this technique and are familiar with how to do it"

Mark probably is, but I'm not, would like to hear about it. Also, I recently bought some 4600 powder, and was told to get the carbon content up in it, to add some graphite. This powder will be used in a canned mosaic process. Is this along the same lines?

[Chuck Burrows]

Pack Hardening -

To case harden a part (the process is also known as pack hardening) the finished low carbon steel part is placed in a sealed container, packed with a high carbon compound. In the old days this was simply animal hide or bone. The container filled with parts and carbon bearing material was brought to a red heat and held at that temperature for a time determined by the size of the part. The time might be from a half hour up to several hours. As the bone or hide became carbon in the container, and a carbon rich gas formed, some of the carbon would infuse into the surface of the steel. Over time this would penetrate several thousandths of an inch, producing a high carbon surface on the low carbon steel part. At the proper time the container is removed from the furnace and the contents dumped into a quenching bath, usually water with perhaps a surface coat of oil to lessen the shock of the quench. The high carbon surface skin becomes glass hard, but the low carbon body of the piece remains soft and very ductile and able to resist shock. Properly done it made a simple and very durable system for treating metal action parts.

The metal container should be air tight - in th old days they sealed it with clay - Satanite should be a good sealer.

To increase carbon add bone meal - availabel at any garden/hardware store.

Bob/Quench - in the previous post I made on color case hardening they specifically state to stay below 1350F?????

[Quenchcrack]

I gotta plead ingnorance here. My experience with carburizing is entirely limited to gas carburizing in an industrial application. I cannot give good information on pack carburizing with bone meal in a home furnace. I will see what some of my books have to say about it but this may be one of those technologies that is mastered only by a few diehard smiths.

Pay no attention to man behind the curtain....!
-The Wizard of Oz.

[polarbearforge]

I've done some pack carburizing before. Powdered charcoal or graphite will work. We used a box with a removable lid that we sealed with a clay/satanite type mixture. First we put a layer of the charcoal in the box, then the parts to be carburized, then more charcoal. Main thing is that the piece is entirely covered by carbon rich material. Put the lid on and seal it. Heat the whole thing to 1700 degrees and hold it there. We were shooting for a penetration of about .070 inches, so it was held for about 10 hours.

Jamie