using a ceramics kiln for heat treating

ScottRoush

ScottRoush

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Jan 10, 2010
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Hi... I have an old Aim electric ceramics kiln (120/240V, 50 amps, 60 hz, 8 cone) with a kiln sitter ( 120 volt, 20 amps) and an analog thermocoupler. It was given to me by my inlaws and I've never used em before. I'm trying to get a manual from Aim.

Anyway.... Can anybody give me some idea of the best way to use such a device for heat treating steel (L6, 5160, 1084, etc)? It requires the use of cones for the kiln sitter and I'm not sure if I just put in a cone that is rated higher than the temps I need and then just check with magnet or if the thermocoupler can be used accurately.

Any advice would be very much welcome!

Thank you....
 
Mossanimal said:
Hi... I have an old Aim electric ceramics kiln (120/240V, 50 amps, 60 hz, 8 cone) with a kiln sitter ( 120 volt, 20 amps) and an analog thermocoupler. It was given to me by my inlaws and I've never used em before. I'm trying to get a manual from Aim.

Anyway.... Can anybody give me some idea of the best way to use such a device for heat treating steel (L6, 5160, 1084, etc)? It requires the use of cones for the kiln sitter and I'm not sure if I just put in a cone that is rated higher than the temps I need and then just check with magnet or if the thermocoupler can be used accurately.

Any advice would be very much welcome!

Thank you....
Click to expand...

I'm using two modified ceramics kilns for heat treat, originally they were using cones but I've added PID and thermocouple on these. Cones are not accurate enough for heat treat. A moderate PID is not a very expensive investment, maybe you'll need also a SSR and a better thermocouple but you'll test the TC with PID and you can calibrate it...

What is the size of your kiln? Ceramics kilns are very large and the heat distribution is not very well. You need to place your knives next to TC to be more accurate...
Emre

Note: Big kilns also have resistances inside of the door and the power is not cut when opened, before opening be sure it is plugged out. If there are heating elements inside of the door it is a must (though you can put a switch attached to the door that cuts the power immediately when you open the door)...
 
Hi....

I'm assuming a PID is some kind of digital thermocoupler/controller? And what is an SSR?

It is a small kiln.... Maybe 1 cubic foot?

Since I have a thermocoupler (even though it's analog).... I was thinking I could 'calibrate' it by checking the temp readout as soon as a blade goes to non-magnetic.... think that will work?

As to the cone.... I think I have to have one in there for it to work....
 
I'm assuming what you have is a basic kiln without any digital readout and possibly with a dial to control the temp relatively.

What you want is to eliminate any extra wiring and controls. So if ther are any remove them so that you have the leads of the heating elements to attach power to. Get a solid state relay (ssr), pid controller and a thermocouple for the pid.

By eliminating any extra kiln controls you'll be able to use the pid and themrocouple to control the ssr which controls the kilns temperature.
 
PID is a digital controller wired to the SSR (solid state relay) which basicaly shuts on or off the kiln electronically. The PID also connected to a thermocouple (I guess your current thermocouple can be plugged to it). With a PID, you can controll the temperature of the kiln and you can program the kiln to ramp up or down at a rate (for example you can set the PID to increase or decrease the temperature ie. 50 F per hour rate).

Calibration can be done on PID, you just put in the TC to a boiling cup of water and measure the temp. For example if it measures 12 F low you can calibrate it by giving a +12F offset on the PID setup...
Emre
 
Thanks folks!

Yes... It is a basic kiln without digital readout. There is a knob that can be adjusted from hi to low. The only extra stuff I can see is the Kiln Sitter attached to the side. Would you recommend removing that???

And there is a hole in side opposite the kiln sitter that you put the thermocoupler into.

But... In the meantime, I have some blades I need to harden. Are there any issues with just bringing up to high temps, checking the color of the steel and checking with magnet? Any issues with opening the door while the kiln is fired (other than obviously protecting my self from the heat that will pour out)?
 
It depends the steel you use, if it is something like 1084 yes u can do it I guess. The hi and low switches are for glaze and biscuit firings I suppose. The biscuit firing is about 750 - 850 C degrees normally, and glaze firing is higher than 1050 to 1200 C. Maybe the low setting may do the trick, but if I'm right the high switch will be too much for the steel types you mentioned above.

Obviously the electrical shock is the main concern when opening the door while running, also the refractory elements in some ceramics kilns are not resistant to thermal shocks (like opening door while hot) so be sure to close the door after you take the blade ASAP... Good luck...
Emre
 
No... the knob is not a simple high and low... it is a knob that runs from low to high with a bunch of numbers in between... a continuous adjustment. Sorry if I implied that!

The blade I need to get on relatively soon is L6 sawblade steel. But I have some 5160 and 1084 too... I will wait to get this thing figured out before I use it for the 5160...
 
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