When do you put...

[claymoore]

your knives in the kiln? When it reaches temp or do you set it and let the blades just heat up to temp. I thought you do the latter just put them in the rack and wait till the alarm rings when it hits the temp for whatever soak it 's set for. Am i wrong?
Thanks Clay

 

[Wloch248]

Yes you are wrong

The reason being the kiln has temp swings as it is getting up to heat. The temp can over shoot by a bit during the cycles of warming up. You need it to be at a stable temp before you put your blades in.

It doesn't take very long for a blade sized piece of metal to warm up.

 

[SBuzek]

Depends,What kind of steel,On my SS blades I start with a cold kiln,Wrapped blades are put in and the program is started,it goes through 4 heating steps to get to austinizeing temp.
On carbon steel blade I bring my kiln up to temp and let it stabilize for about 30 min,then put the blade in and soak to 5-10 min.
Works for me,YMMV.
Stan

 

[SteelSlaver]

Depends on your setup. I now have a programmable controller so I set it up to hit 50f below my desired temp hold that for a bit to let everything get stable then slowly ramp it up the last 50 then soak. You can do the same thing without a programmable by setting your temp low then moving it up yourself. About the same as Stan.

Not only are you dealing with the refractory and everything else getting up temp so that the thermocouple/PID are reading right and working to hold the right temp, you have the fact that the elements are often radiating temp well above desired temp. The element of course has to be hotter than the area it is heating to raise the heat. When the PID is trying to raise the temp a lot it will have the elements switched on almost constantly and the elements themselves reach very high temps. Once it is at or near temp it switches them on for short periods and they do not reach their top temps.This radiated heat can over heat a thin exposed piece of metal like your edge, the closer to the coils the more apt it is to happen. If your thermocouple is shielded from the radiated heat by a sheath or blades between it and the elements it also will not be responding well to this radiated heat.