Leaving knife in kiln while heating up...

[Dillon Rudder]

I tried searching the forum for this first but seem to get information that's not as specific as what I'm looking for...

What is the general consensus on putting the knife in the kiln at room temperature and letting it heat up with the kiln vs. getting the kiln to temp THEN putting the knife in for the soak/quench?

I've always put them in at room temp but I'm starting to wonder what effect that has on all that time I spend normalizing and whether or not it negatively or positively effects grain structure, or if it even matters at all.

Thanks in advance!

 

[MBB]

It affects the degree of decarb/oxydation. Longer time at (or getting to) temperature = greater decarb.

 

[DevinT]

Simple alloys would be most affected. They don’t do well with long soak times and you’ll get grain growth.

Higher alloy steels would have less grain growth but would have more decarb if left unprotected.

All steels have recommended soak times. I run two furnaces, one to preheat, and one to austenitize and both are brought to temperature before use.

Hoss

 

[SBuzek]

On carbon steels i bring the kiln to temp and let it soak for 30 min before putting in blades
On stainless steels wrapped in foil I put in a cold kiln and run my program which has 2 soaking steps and final temp.

 

[Tenebr0s]

If you put the knife in at room temperature, you will absolutely overheat the blade as the oven comes up to temperature. IR heat from the coils will transmit to the steel faster than to the air. I always let my oven soak at temp before putting in the blade.