Temperature Controlled Furnace?

I was reading my blacksmith group newsletter, and somebody wrote up about a homemade temperature controlled propane oven using industrial controls to turn the propane on and off. He used an Omron E5CN controller with a Type K thermocouple. He warned you about the safety issues, never run it unattended, be sure you have a pilot light to ensure relight of the burner, etc., but it still seemed scary to me. I would feel safer with an electric furnace, potentially using the same controller.

I built a simple (5 gallon bucket) propane forge with a Reil burner, it works fine, but of course no temperature control other than keeping an eye on the color of the steel.

A friend of mine took a used household kitchen oven ($25), put on his own controls, and uses it to bake powder coating on metal parts. I think he goes up to 450F or so. Not sure how hot the self-cleaning ovens will go, I tried to look it up on the web but came up dry after a few google searches.

I am not necessarily interested in heat treating tool steel, but I am interested in forging aluminum, which I understand has a narrow temperature range for forging, 600 to 800 F. On the other hand, if I am going to the trouble to make a temp-controlled oven, I might as well go all the way and design it for a wide range of temperatures, to allow it to be used for multiple purposes.

I understand that ceramic kilns can be used for that purpose, and perhaps a used kiln would be a good place to start modifications. However, for forging, one would need to take the part out and put in back in multiple times, especially since I am not a skilled blacksmith.

I did notice that some knifemakers use nitrogen to reduce oxidation.

Comments? Useful web pages?

Richard Ferguson

Reply to
Richard Ferguson
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Ceramic kilns tend to be top loaders. No problem for ceramics which are always allowed to cool slowly before being removed. Fishing something red hot out of a top loader is an extra complication best avoided if you can by constructing a side loading oven. Heat after all, goes up, which cools off the oven and warms you, possibly more than you would like in both cases.

I picked up a temperature controller with relay and thermocouple on e-bay, new, for $100 CDN. It controls up to 1200 C

I am going to look for insulating firebrick and silicon carbide heating elements. This outfit seems to cater to dabblers like us:

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Reply to
John Ings

Apart from normally being top loading, ceramic kilns are not designed to sheild the elements at all - fine for a load of pots, could be unpleasant with a hunk of metal when the elements are electrically live.

Reply to
Ecnerwal

Have a look at this link

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SiC elements are not as easy and cheap to use and implement as wire elements like kanthal. Wire can be used with a c>>

Reply to
David Billington

But I suspect it will be harder to place wire along the roof of the oven where I want to keep it, up out of the way of stuff going in and out.

But that doesn't have to be under the control of the temperature controller does it? It can be seperate and only adjusted infrequently when needed?

Reply to
John Ings

controls, and uses it to bake powder coating on metal parts. I think he goes up to 450F or so. Not sure how hot the self-cleaning ovens will go, I tried to look it up on the web but came up dry after a few

A household oven works fine for powdercoating without any modifications. I have an old oven in the shop that I use for powdercoating, 450 to flow out, 400 to cure. In fact, its a self cleaning oven, but I've never put it through that cycle. I think that self cleaning ovens go up to 700-800 deg. I don't know if they could maintain that temperature for long enough to do heat treating, though.

Gary Brady Austin, TX

Reply to
Gary Brady

Wire on the roof of the oven is common in glass fusing/slumping kilns and they may only have wire on the roof. The wire is fitted over ceramic rods for support .

When I looked at the SiC and phase angle c>>

Reply to
David Billington

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