heat treating furnace design help

Sam Salvati

Sam Salvati

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Aug 6, 2007
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Would this work? 1" thick inswool/kaowool coated with satanite refractory all around the inside, burner port at one end, with a fire brick in fornt of the flame to disperse/baffle the heat, with the blades never extending over the firebrick and flame itself. ID is 10 inches, would this be suitable for heating blades nice and even to the proper temperature? I would use just the PSI valve to control the heat with a thermocouple to measure how hot inside it is and control it from there. I know it wouldn't be as good as salts or an electric oven or kiln, a bit oxidysing, maybe a bit uneven heat but much more ideal than using just the forge.




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Sam, Your baffled oven will work, but needs a lot of technical changes to be efficient for heat treating swords.If you want a heat treating oven for long blades, you need a different setup. First, for a more even and efficient heat, use 2" of wool. Second, if you want to avoid hot spots from the flame, and the problems with oxidizing/reducing flames, just isolate the blade from the flame entirely. The way this is done easiest is to make a long tunnel forge with a five inch round front and rear opening. Have one burner for each foot of body length,with the end ports 6" from each end (for a 36" oven that would be at 6",18", and 30"). Place a schedule 80 piece of stainless (312/316) pipe through the forge,with about two inches sticking out each end. Weld two 1" spacers at 4 and 8 o'clock position in the openings on the ends to support the pipe in the center of the doors.This will allow the exhaust gasses to vent.
Make a plug for the pipe ends from soft firebrick. Plug the back and mortar it in with satanite. Put your thermocouple probe through this plug, sticking down the tube. Use the longest practical probe. A 1/4" by 16" monel probe will work great. Use the front plug as a stop to keep oxygen out of the pipe. This pipe is called a muffle. The temperature inside the pipe can be very evenly controlled by allowing the forge chamber to come up to heat and stabilize.After about 15 minutes, the muffle should be stable at the exact temperature the controller is set at (using a PID and a solenoid valve to regulate the gas supply). If you are not using a controller, you can adjust the flame with a needle valve to get a pretty close temperature control.
Wrap a single sheet of notebook paper around the blade, and pace the blade in the muffle, putting the plug on quickly. The burning paper will eliminate all the extra oxygen.
Stacy

PS: This same forge can be used without the muffle to forge long blades.
 
SO basically like a salt tube without the salt Stacy? Do you mean like this? I am sort of familiar with this design when using coal or charcoal, but basicaly that way is just to put a pipe in the forge and let the blade come up to tempe inside the pipe.

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That is pretty much it.
You can use it horizontal or vertical. I would put the thermocouple in the bottom cap if it was run vertical. In a vertical unit, you usually have to add an exhaust manifold or port of some sort, since the bottom is not vented, and the top around the tube is not a desired place for a huge flame. I would add two exhaust ports on the side opposite the burners, with 6" long "exhaust pipes". Line these pipes with 1" refractory. If you use a 5" pipe with 1" wool it should give you a 3" port. Two of those should be enough to vent the input of three burners. Basically, exhaust ports needs to total a minimum of 300% of input ports.
Stacy
 
OK cool thanks alot Stacy. Have you run this type before?

Would the first type work though? I wouldn't be so worried about decarb so much as i wouldn't be soaking the blade for long periods of time, and would grind off most of it. more insulation would make for more even heat, would a larger ID make for little to no hotspots?
 
I was at an ABS hammer-in in No California and Don Fogg had a HT furnace made out of a 55 gallon drum layed on its side here is a link by the way he'd move the burner to the lower rear side of the furnace that I saw giving a swirl flame from the rear.
 
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