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hawgwrench
03-30-2009, 05:22 PM
The wife has a couple ceramic pottery type kilns that are wired in to my shop...while propping and paying homage to the beer gods,it occured to me these things may serve a purpose other than housing the errant spiders I've got running around. The larger of the two maxes out @ 2300 degrees and has a timer that goes in hourly increments up to 18 hours,the smaller at 2000 with no timer, by now your following my thinking. Will either or other of these things work for heat treating? The smaller is alot better size wise,prolly a 6x12x12 opening and 110 volt,the larger is about size of a beer keg and 230..

The Doctor
03-30-2009, 05:29 PM
Yes, they will. But you need to buy or make a temperature controller.

Ed

camdigger
03-30-2009, 05:42 PM
From the description of the heat cycle, there is already some kind of controller. Either furnace should heat well up into the orange color range that will do for hardening. The next question is how well do the kilns ok in the 300 - 600 F range for tempering?

wierdscience
03-30-2009, 08:22 PM
Ceramic ovens work fine,they even work for melting aluminum for casting.

The controls they have cycle on and off over a long period of time until the furnace comes up to heat.To limit the temps they use a slump cone to hold the switch closed.When the furnace reaches the desired temp,the cone melts and sags opening the switch and shutting off the power.

Like mentioned you will need a control.A PID controller,a power relay and a type K thermocouple will be about all you need.

A friend showed me his aluminum melting one about two months after my mother sold her kiln for beans.He simply used the existing control and cut a 4" exhuast/flue hole in the center of the lid.80lb melts of aluminum were no problem for him.

Forrest Addy
03-30-2009, 11:02 PM
Yup, a ceramic kiln make a fine HT furnace except for two things: Temperature control and atmosphere control.

Temperature control is easy to fix: add a suitable temperature controller. The one I suggesat is a cheap import. It will ramp to hold temp and down etc. Here's a link of a cheapo eBay produce:

http://cgi.ebay.com/PID-TEMPERATURE-CONTROLLER-4-Kiln-Oven-Espresso-Machine_W0QQitemZ150335819708QQcmdZViewItemQQptZAU _Business_Industrial_Restaurant_Catering_Equipment ?hash=item150335819708&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C 240%3A1318%7C301%3A0%7C293%3A1%7C294%3A50

You can spend lots more money and get a better one that will do pretty much the same thing. You will need a proper type K thermocouple with a long well for working with high temperatures. Here's a link to such a gadget:

http://cgi.ebay.com/K-Type-Thermocouple-Probe-f-Digital-Thermometer-1832-F_W0QQitemZ310131113244QQcmdZViewItemQQptZLH_Defau ltDomain_0?hash=item310131113244&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C 240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

There are other details to cover like thermocoupls connectors, zone control etc but you can research these out.

Last comes atmosphere control. Atmospheric oxygen is a PITA when heat treating. I caused to work to scale, surface decarburize etc. An inert atmosphere woiuld be cool but the usual trick it to use stainless steep part wrap with a strip of brown paper inside. Wrap up the work like a piece of chicken with foil except use this stainless stuff. It's kinda expensive. The paper by the way carbonizes and scavanges the ozygen in the air trapped inside. Another trick is to toss in a few charcoal brickettes. Not too many or they will take over and you'll lose ccontrol over the heat cycle. PLace them when you determined there are air leaks. Locate the kiln out of doors when using charcoal for atmosphere control. The charcoal produces carbon monoxide. It's not hazardous particularly bit you do need good work site ventillation and an awareness of the potential.

dfw5914
03-31-2009, 12:05 AM
... The next question is how well do the kilns ok in the 300 - 600 F range for tempering?

That's what the oven in the kitchen is for:D

lakeside53
03-31-2009, 02:02 AM
There's also this one - 64 step program... Themocouple and SSR included.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=200319740696



And it's $48 brother
http://cgi.ebay.com/PID-Temperature-Controller-SSR-Kiln-Furnace-Fah-Celsius_W0QQitemZ200324146535QQihZ010QQcategoryZ50 926QQcmdZViewItemQQ_trksidZp1742.m153.l1262?_trksi d=p1742.m153.l1262

Forrest Addy
03-31-2009, 04:10 AM
Laleside, Yup that's a more talented controllers and it can be split into two zones. However, you really need a long sheathed thermocouple or an extended well for a hi temp-thermocouple. Sticking the braided of T/C through the insulation is a sure way to have it fail early and often. The thereemocouple people have a better reasoned discuttion of the whys than I.

derekm
03-31-2009, 05:17 AM
Last comes atmosphere control. Atmospheric oxygen is a PITA when heat treating. I caused to work to scale, surface decarburize etc. An inert atmosphere woiuld be cool ...

Couldnt you use Mig welding gas for this?.. i.e. Argon +C02. since mig welders usually a flow regulators attached to bottle. A couple of litres a minute would
probably do

Forrest Addy
03-31-2009, 05:52 AM
Dceleron

Inert gas I would think so if the flow was low enough not to carry off heat. Flammible gas would work too except for the gush of flame when you open the furnace - and there is the fire hazard.

Sparky_NY
03-31-2009, 07:02 AM
Couldnt you use Mig welding gas for this?.. i.e. Argon +C02. since mig welders usually a flow regulators attached to bottle. A couple of litres a minute would
probably do

That would work but it pretty pricey for this application. Nitrogen is the cheapest of the bottled gases and would work well. The problem is you would have to seal the kiln up pretty good to allow the smallest flow possible, even then a tank won't last very long flowing steady.

camdigger
03-31-2009, 10:54 AM
Gaseous nitrogen in contact with steels at elevated temperature may result in at least a shallow layer of nitrided steel which will have different properties than the original?

Some protextion from the ovens oxygen rich atmosphere can be obtained byrubbing a bar of handsoap over the work before the first heat.

PID controllers and timers are luxuries for Redneck heat treating. True hillbilly heat treats are done with a heat source, temp judged by eye, and the quench done by plunging into a tin juice can full of fluid. Followed by tempering done with a heat source and the temp judged by surface oxidation colors.