Tempering Question

Merle

Well-Known Member
Question for you guys.... What is the reason for doing tempering in separate shorter cycles, as opposed to a single longer cycle. For example many recommendations are something along the lines of "temper at TWICE at 400F for two hours each"

What would be the difference in just doing a single longer soak at the prescribed temperature (e.g. 4 hours at 400F)? Does cooling back to room temperature periodically achieve something in the steel?

thanks, andy
 
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Doug Lester

Well-Known Member
Actually it may not make any difference depending upon the alloy in question. Cooling may trigger retained austenite in some alloys to convert to untempered martinsite and a second tempering cycle will will temper it. Most of the change caused by tempering will occur in two hours so if I were to do two cycles I would do two one hour cycles. Three cycles would be overkill but they wouldn't hurt anything. Nor would accidently leaving the blade in the oven overnight.

Doug
 

Chris Railey

KNIFE MAKER
Nor would accidently leaving the blade in the oven overnight.
That sounds like something I might do. Man that would drive my wife crazy. I have a toaster oven With a seperate thermometer I do mine in because it has a 2 hour timer. So if I forget it will turn off without me. Safety first...trusting my memory...dead last.
 
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