EN32B Steel

The atmosphere around the latter contains significant amounts of oxygen (and nitrogen) and any carbon is presumably in the process of being oxidised, rather than trying to diffuse into the surface of the steel. Which is why the former process requires to purge and exclude external gases and maximise direct contact of carbon with the surface. The carburisation process requires temperature, time and a significant concentration of carbon on the surface of the steel. Although there are some related processes that rely on hydrocarbons etc for surface treatment, those processes tend to be very complex and challenging to implement.

Murray

The use of stainless steel shim suggested itself from a video on Tom's Techniques website when he was case hardening a small part. He wrapped the small part complete with case hardening material in SS foil which he got from some craft shop/website. I couldn't seem to source it this side of the pond and thought SS shim, I have it in various sizes to 6 thou, would do (not done it yet!). You do have to fold it over and over and crimp it best as can to exclude the air, and he recommends putting in the parcel a little combustible material to deliberately burn and consume the oxygen remaining in the ss foil wrapped parcel. Not sure how thick the shim would have to be, too thick and it'd be a swine to fold and crimp air tight, too thin and I suspect it might burn away in a really hot fire.

Now an article in MEW on building a simple electric furnace would be very interesting, so +1 on that idea Neil!

Chris

Edited By ChrisH on 22/12/2017 14:59:51

I made an electrically heated salt hardening furnace some years ago. It lasted long enough to do what I needed it for, but it wasn't all that safe and the heating element got a hot-spot and melted soon after. It's here if anyone's interested:-

**LINK**