Dumb forging question

G

ghost squire

Joined
Feb 1, 2004
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I don't forge knives at all, I was wondering, is it expected that carbon will be lost from the steel in the forging process? How often does this happen and how much is lost?

Does it happen more or less with charcoal forges versus gas ones?

Or, is it just that the outside layer of steel is converted to scale when its decarburized, so when you scrape it off you have fresh steel on the bottom?

Thanks!
 
Yes,Yes,and Yes.
Carbon will combine with oxygen and be removed from the steel at any temperature above 1275.The length of time and amount of oxygen present are the factors that determine the amount of decarb a blade undergoes,and how deep it reaches.The "rind" or decarb layer is ground off in the final finishing after quench.The reason salt pots are popular is the exclusion of oxygen.Stainless steel requires total exclusion of oxygen or the steel will be horribly damaged at the 2000 degree temps involved in HT.
If the fire is made right a coal forge is great.A gas forge can have the air mix adjusted to a good reducing atmosphere,also.
A certain amount of carbon is lost on any forged blade.It is not a problem if forging is done with skill and the temperatures are kept in the proper range.
 
It's not the forging itself that causes the decarb but the exposure to an oxidizing atmosphere at heat treating or forging temperatures ! The decarburization goes deeper than the scale .For those who forge you will have to grind off enough metal to remove the decarburized layer.For those buying material for stock removal - hot rolled annealed condition will have a decarb layer if you don'e want decarb get hot rolled annealed and precision ground. The grinding will get it to precise size and will take off the decarb layer. Remember that checking hardness with hardness tester or file a decarb layer will show up as low hardness !
 
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