Heat treating furnace design.

[ApprenticeMan]

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.

[habu68]

here is a link to a heat treating company and a stainless steel bag that they use to keep oxygen form de-carbonizing parts http://www.nabertherm.com/produkte/w...2_englisch.pdf

you might find some ideas there. Check out pages 8 and 9

[ApprenticeMan]

I am not so worried about decarb, i won't be soaking the blades for a couple hours so will grind off whatever decarb there will be.

[RainsFire]

seems kinda deep with alot of wasted space, unless the blade is proportionate to a smaller blade.. but I'm assuming it is a full length-28in +/- so ya.. Don-fogg has a controlled propane heat treating furnace, but I cant remember what it looked like.

wouldn't the blueprint for the tube furnace or whatever it was where the burner blasted down the length of the forge instead of through the side work relatively well also?

anyway, nice rough design!

[m_brothers]

Why not make the furnace smaller so that it needs less heat and you waste less propane/natural gas/energy. Anyhow, it's a nice design. What would you use for a shell to put the kaowool in?

[RainsFire]

exactly what I was thinking^^

I have a feeling he would just lay the kaowool in place to be held down by the refractory(which you might want to do without if possible). Refractories are usually more just as a protection from flux, and I have found kaolwool to distribute and achieve heat faster than firebrick and satanite refractory.

cool stuff man.
you might also want multiple burners too..I dont know how you would engineer that, but ya.. more heat disperesed.

[ApprenticeMan]

Originally Posted by RainsFire

seems kinda deep with alot of wasted space, unless the blade is proportionate to a smaller blade.. but I'm assuming it is a full length-28in +/- so ya.. Don-fogg has a controlled propane heat treating furnace, but I cant remember what it looked like.
wouldn't the blueprint for the tube furnace or whatever it was where the burner blasted down the length of the forge instead of through the side work relatively well also?

Originally Posted by m_brothers

Why not make the furnace smaller so that it needs less heat and you waste less propane/natural gas/energy. Anyhow, it's a nice design. What would you use for a shell to put the kaowool in?

It is easier to heat a large space evenly than to heat a small space evenly. It is not a forge, so it doesn't need to heat the steel to a proper forging temperature, only at most 1600F-1650F. That tunnel forge design is WAY too hot, again we are not talking about forging temperatures, and the heat would NOT be evenly dispersed in any way. great for forging when temperatures don't need to be so closely controlled, but ruddy for HT. MB, an old compressor tank or a 45 gallon drum.

Originally Posted by RainsFire

I have a feeling he would just lay the kaowool in place to be held down by the refractory(which you might want to do without if possible). Refractories are usually more just as a protection from flux, and I have found kaolwool to distribute and achieve heat faster than firebrick and satanite refractory.
you might also want multiple burners too..I dont know how you would engineer that, but ya.. more heat disperesed.

refractories are much more than protection against flux, heck flux eats thorugh quite a few. It is all about keeping the heat in. Multiple burners would make for more heat, and make it harder to tune both for an even heat along the whole length and not end up with hot spots. The idea is to heat the AIR inside evenly, which will give you your even heat. The flames should not even be heating the blade directly.

[RainsFire]

yes well, theres the dillema.. even your design will have a hot spot near the rear of the furnace.. that fire brick will absorb alot of the heat, and the entry (front) will be a considerable ammount cooler. really, you need more than one burner to disperse the heat more evenly. As you've said, you do not want to heat with the flame, but it is nearly un-avoidable with this sort of system. If you had a seperate air heating furnace that circulated the heat through the box at high temps, thats different.. but highly un-efficient, and you could just as easily be using salts..

seriously check out Don foggs.. I'll root around for the picture.

[ApprenticeMan]

I have seen Don's. Basically the same with a smaller ID of the furnace. it's actually more efficient than a forge, as you are not operating at anything higher than 3 to 5 PSI at MOST, so much more efficient than using the forge to heat treat. And efficiency is not so much an issue, spending alittle more gas to get consistent even results IMHO is well worth it. It is also not to scale.

[welder19]

How about like this, please excuse the rough drawing, I just sketched it up real quick in paint, I think it would heat more evenly but 2 burners might be better.

welder19