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Protect from decarb during a sub critical anneal?


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Is it a good idea or necessary to protect the surface of your knife from decarb during a sub critical anneal?  I am using 80CrV2 and it will be in the oven @ 1300F for an hour.  I have been protecting the surface with tool wrap, but obviously it would be better to not bother with the extra expense.  I don't care about minor decarb, but if it goes pretty deep I would prefer to protect the surface.

 

I am not sure how much decarb will happen at such a relatively low temperature.

 

This anneal is being done after forging, normalizing and 2 grain refining steps, but before any grinding is done.

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There's no need to leave it in for an hour, a five-minute soak will do fine.  Decarb should not be much an issue at 1300 anyway, but certainly not with a short soak.  If you really want to keep protecting it, but with less expense than tool wrap, anti-scale powder or paste is a lot cheaper and works as well.

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Personally I don't think I would worry about it.  If you really wanted to be sure you had no problems, a quick coating of graphite spray would be cheap and easy.  You certainly won't get appreciable carbon pickup (carburization), and it would act as a sacrificial layer to protect from oxidizing.  Also, if you just burry the blade in sand while at temp that will reduce exposure to atmosphere and thus reduce decarb chances.  

 

ETA:  Heh, Alan and I posted at the same time.  

Edited by Jerrod Miller
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Good deal! Since my goal is to do a bit of a spheroidizing anneal, I will just soak it at 1300F for 5-10 minutes and bury it in my bucket of wood ashes I already have.

 

That seems like better time spent than wrapping it and waiting an hour.

 

Thank you gentlemen!

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