6 hour temper?

Matt Rochester

Matt Rochester

Joined
Nov 28, 2014
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So long story short is I messed around and forget about my knives in the oven. So, I HT'd, subzero, 1st temper at 465 for 2 hours. I then cooled in water and tempered again for 6 hours. I'm going to check the hardness tomorrow and see where it landed. Would the extended temper time cause any problems? As long as my hardness is good am I good? Thanks.

Forgot the steel type. Cpm154.
 
I think you'll be fine. I have had to put some blades (carbon steels) through as many as 15 two hour tempers (to get all the wiggles out). I asked my teacher who is an MS about it. He said It's fine. As long as your temper was in the right temp range you should be ok.
 
The Crucible Industries data sheet on CPM 154 states that hardening should happen with a Pre-heat to 1400 to equalize, then austentize at 1900-2000 and hold for 30-60 minutes. Oil quench to below 125, or salt quench to 1000 then air cool to 125 ("salt bath treatment, if practical, will ensure the maximum attainable toughness").

Temper should be twice at 400-1200 for a minimum of two hours each time, BUT: tempering between 800-1100 "will result in sensitization which causes a minor reduction in both corrosion resistance and toughness. We recommend that this tempering range be avoided."

So, as long as you kept it between 400 and 800, I don't think you could have done any damage to the steel at a molecular level.

http://www.hudsontoolsteel.com/technical-data/steelCPM154
 
It won't be a problem. If you lost even 1/4 RC point I'd be surprised.
 
seems i've read a few posts of guys forgetting blades in their ovens/kilns. I wonder if a timer relay on a contact or the contact for the element save some heart aches or be worth it.
 
I need to put a timer on mine with an alarm. Im eventually ping to get a programmable PID as mine is just a plain ole digital one.
 
You can do some fairly good control with digital. What kind of temperature controller do you have? They often have inputs and outputs behind them on the terminal board
 
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