junker Posted August 23, 2009 Share Posted August 23, 2009 ok sorry but this is gonna take an explanation before i can get to my question. since case hardening is essentially getting steel hot and putting it in carbon causing the steel to "soak up" the carbon... when we put steel into a fire aren't we doing the same thing when we heat steel in a coal or charcoal fire? so wouldn't that make any steel you put in the forge actually a higher carbon content? Quote Link to comment Share on other sites More sharing options...
Frosty Posted August 23, 2009 Share Posted August 23, 2009 Yes it does soak up carbon from the fire provided it's a reducing fire. No you aren't working with higher carbon steel because in the short time the steel is in the fire the carbon doesn't have enough time to get much farther than the second molecule and the scale formed when you withdraw the steel from the fire eliminates far more than that. Frosty Quote Link to comment Share on other sites More sharing options...
junker Posted August 23, 2009 Author Share Posted August 23, 2009 ok thanks for the info Quote Link to comment Share on other sites More sharing options...
matt87 Posted August 23, 2009 Share Posted August 23, 2009 Carbon migration is proportional to temperature. Keep a bar at welding heat in a reducing fire and it will carburise quicker than at red heat. However as Frosty said it's still a slow process and the carburised layer is usually scaled off faster than it's built up. It is theoretically possible to add a useful carburised layer in the forge and it has been discussed with regards to Roman smiths with their enclosed forges. Blister steel used to be produced by laying bars of Norway (wrought) iron in hermetically sealed cases of powdered charcoal and kept at a red heat for a week, and when it came out it still needed to be folded and welded to homogeonise the carbon content. Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted August 23, 2009 Share Posted August 23, 2009 There are some lengthy discussions on case hardening, here is the link to one of them:http://www.iforgeiron.com/forum/f52/case-hardening-alloying-6069/ Quote Link to comment Share on other sites More sharing options...
John Martin Posted August 23, 2009 Share Posted August 23, 2009 Also, if you heat up a piece of steel to many times in a forge. Especially a gas forge, you suck a lot of carbon out of it. This is why when bladesmithing it can't take you tons and tons of heats to forge out your blade. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted August 24, 2009 Share Posted August 24, 2009 A classic example is that of the traditionally made japanese sword. They start with tatara made tamahagane steel that can be nearly 2% carbon and after the repeated folding and welding in a charcoal fire they end up around 0.5% C. Quote Link to comment Share on other sites More sharing options...
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