Hmmm Designing an Electric HT Salt pot rig

W

Will Leavitt

Joined
Jul 28, 2006
Messages
3,953
J's thread about his electric oven got me to thinking (dangerous on the best of days, ill advised on the others) about building an electric salt pot rig. Instead of using brick I could use all the kaowool and add Satanite as a refractory inside the tube.

For those of you with the math background would this be practical using 110volts? :)

Is one rig better than the other for heat treating carbon steels? I do use antiscale compounds during heat treat so scaling isn't a consideration.
 
Can you use a salt pot to heat treat stainless steel?
I'm sure that's a retarded question for some of you guys, lol, but I don't know!! :D
 
Michael, you bet! In most ways it's preferable to other methods in that the salt heats the steel uniformly and quickly, and there is no scale after quench. Many people quench in somewhat cooler salts too.

Will, I think most are fired with propane and use a solenoid valve hooked to a thermocouple to maintain the temp. The solenoid would run off 110, I'm sure. But I could be all wet - whenever you get yours built I'll be real interested in your method and your source for stainless pipe.
 
I'm sure Kevin will chime in here, but you can get some unpleasant experiences when you mix high voltage and hight temperature salts. The problems with a metal clad chamber, a metal tube, conductive liquid salt, inserting a metal blade...... well you can figure out the problems.
A low temperature salt pot, for tempering ( and martempering/marquenching ),is a fairly safe electric setup. It can be run off 110. A small salvaged pottery kiln, a pid, and a schedule 80 stainless tube will be what you need for the conversion.
Stacy
 
Mnay people have ahd different experiences, but I would never go back to a hihg temp electric setup now that I have had a taste of gas. It is mostly due to the near impossibility of keeping the *#%$*@$% high temp salts inside the %@$!*& tube:grumpy:! Gas doesn't give a rip about salt in the burn chamber.

For the low temp you do NOT need stainless and the thinner walled tubing is better, so it is very inexpensive to setup. I have had some awful experiences with low temp salts and kilns but that has went away entirely since I got fanatical about keeping moisture out of my salts.
 
I've talked with my teacher and he recommends the salt pot, the high temp salt pot I'm going to build doesn't have any room for the salts to get inside the heat chamber unless they eat through the walls of the salt tube.

The construction would be a 4" SS salt tube with the electrodes wrapped around the tube an outer shell of 6" pipe. Pour 1" of satanite in the bottom of the 6" tube, put the salt tube in the body then fill the rest of the space with satanite. I asked about the salt tube being grounded out, he says in theory it's just like an electric plate and is safe as long as the electrodes don't ground out to the body. Sounds pretty simple to me.

The main thing I'm asking is all things being equal (scale/decarb, time, costs) would you rather have a salt pot or HT oven?
 
Will Leavitt said:
The main thing I'm asking is all things being equal (scale/decarb, time, costs) would you rather have a salt pot or HT oven?
Click to expand...

If they were equal, the HT oven, easily. Until air starts holding and transferring heat in a manner equal to molten salt and until air inhibits decarbeurization like molten salt, I'd think the salt pots are the better choice.
 
bladsmth said:
you can get some unpleasant experiences when you mix high voltage and hight temperature salts. The problems with a metal clad chamber, a metal tube, conductive liquid salt, inserting a metal blade...... well you can figure out the problems.

Stacy
Click to expand...

Probably not recommended for us clumsy people.
 
Will, With all due respect to your teacher ( who I know nothing about), he has left several important factors to the design of a pot like you described out. Not the least is the large amount of expansion that a 4" cylinder will undergo at 1500F to 2000F. They expand about 1/2" at operating temperatures ( something around 10-15%).

The "in theory" part of his explanation was compared to a hot plate. That is about the equivalent of comparing a cigar lighter to a venturi forge. Both operate about the same, but you won't catch me putting my face about 2" from the door of a forge.

"In Theory" ,it is D**m near impossible to keep the salt out of the heating chamber of a high temp salt pot.
Stacy
 
No offense taken about my teacher but he says he's seen and used the described rig.

I'm not going to build it at the moment because my fiance isn't keen on the whole molten salt volcano threat. I'm going to build a heat treat oven instead.
 
Also to add to what Stacey has said, if you wrap your heating coils around a metal pipe they will become short circuited and burn out unless you take precautions to insulate the coils from touching the metal pipe
 
Will Leavitt said:
I've talked with my teacher and he recommends the salt pot, the high temp salt pot I'm going to build doesn't have any room for the salts to get inside the heat chamber unless they eat through the walls of the salt tube...
Click to expand...

That is exactly how my salt always got inside, I never had any drip in for the outside. The high temp salts are the most invasive things I have ever seen when it comes finding any weakness in that tube and getting through it in no time. If your welds are perfect those salts will find any little carbon concentration or inconsistancy and eat their way out. I have been through many tubes until I went with gas and decided to just let the little pin holes weep and the gas will ignore them.

With electric I always instantly knew when there was a pinhole since even the vapor of the salts is conductive. Current would get picked up from the kiln elements and taken to the tubing wall, the salts, and the steel workpiece I was holding:eek:. To avoid rather interesting sensations I recall more than once finishing a heat treat standing on a rubber mat tossed over a plastic bucket.
 
Any recommendations for a resonably priced Normally Closed (NC)gas solenoid? I am looking for a place to order and a part number if possible. Thanks!
 
You must log in or register to reply here.
Back
Top