Tempering question

[SVanderkolff]

I am going to be tempering the back spring for a lockback folder. The back is 440c and currently at 60 Rockwell after heat treat. I plan on putting the spring into the kiln at 975 f for 2 hours to bring the hardness down to around 52. Which seems to work well for these springs. My question is after the 2 hour soak will it hurt reduce my hardness significantly if I leave it in the kiln to cool as the kiln cools. This would be a very slow cool probably around 4 hours.
Thanks
Steve

 

[Drew Riley]

Why leave it in? I'd just pull it out, cool it off in a water bucket, and get straight to clean up...

 

[SVanderkolff]

MOstly because I may not be here at the end of the cycle to pull it out. Life tends to intrude. I am not worried about the kiln running when I am not here since my heat treat room is concrete on all six sides.

 

[Karl B. Andersen]

The flexibility of hardened steel is as much about geometry as it is about hardness. Actually, it's more about geometry.
If you get it too soft, it will acquire fatigue in use.
If I was you, I'd wait until I could baby sit the temper cycle and remove it when it's done.