Low Temp Salt Pot

J

JMJones

Joined
Jul 14, 2010
Messages
945
I am contemplating building a low temp salt pot only. Anyone have any plans or wips ect?

The reason I am thinking of low temp salts only is because I grind my blades after hardening so decarb is not an issue and I only ht one to three blades at a time. I am more than satisfied with using a kiln for hardening. However long, thin kitchen blades warp on me almost every time, and that is all I really make. This is still doing multiple normalizing heats and sub critical anneal. I am thinking that the low temp salts my reduce the stress on the blade and give me multiple attempts at getting it as straight as possible before Martensite formation. Does this sound reasonable?
 
Mine is a small used pottery kiln ( free). I cut a hole in the top to fit the salt tube. I converted the kiln to PID control the same way as in the sticky on converting a toaster oven. The PID is connected to the SSR, and the SSR is wired to a standard 120VAC 15 amp socket. All this is in its own box (HF tool box). I set the kiln dial to HI, and plug the kiln into the socket on the PID box. The TC from the PID is in the salt. The PID does the rest from there. I can plug any 120VAC device into this ( toaster oven, heater strip, oil tank warmer rod, etc.) and just put a TC in/on the controlled device.

I welded a bottom on a 4"X16" stainless heavy wall tube. It sits in the kiln with about 6" sticking out. I wrapped the exposed part in a 4" wide strip of kaowool, and attached a #10 coffee can with both ends cut out as the shell to cover the wool. IIRC, the wool overlapped itself by a couple inches to make it fit the outer shell snug. I poured about 3/4" of satanite on the wool to seal it to the pipe and make the "salt proof" top over the wool. That left a 1" lip on the salt tube sticking up above the satanite, with the coffee can slightly higher than the tube lip. I put the coffee can lid on when the salts are cooled off. The salts are hygroscopic, and need to be kept sealed from the humid air around here when not in use.

The salts came from HTT&R. They fill the tank to about the height of the insulation....about 2" below the tube top.

The salt pot is in the back of the storage shed right now, so I can't take a photo, but it is a pretty simple setup.

When doing HT for myself use oil or air as a quenchant, and the Paragon for tempering....but most everything gets sent to Peter's...... so the salt pot got stored away until the new shop was up. I plan on doing some quenching experimentation once things are fully functional in the shop. It worked great for tempering, but the paragon is certainly easier easy to setup and shut down.
 
Stacy, do you think there is a hot plate or similar setup that will get a ceramic fiber wrapped tube of salts (6 inch diameter 15 inches tall) to the correct temp range?

Or anything that I could purchase and plug directly into the controller you described that would work?

Thanks
John
 
I have seen that setup used at a seminar. They put the tube of salts on a hot plate and wrapped the whole thing in a inswool blanket. It worked....sort of....but was really primitive as well as very unsafe. There was no support in any way to prevent the tube from falling over if bumped.

Small pottery kilns are really cheap. The trader papers, pawn shops, and other places often have one for less than $50. You don't need to do much more than cut a hole in the lid for the tube, and wrap a inswool blanket around any exposed tube. That and the controller described will run it just fine.

It would be pretty easy to make a basic electric salt pot oven with the tube in the center....... basically a home built HT oven on its end.....just make sure the electric coils stay away from the tube.

With some creative construction, a simple gas burner can be made to heat the tube. Again, basically a vertical forge with the tube down the center. You would need a pilot flame and PID control to turn the burner on and off as needed to keep the tube temperature in the range desired. This is the setup for many high temp salt pots, but could be adapted to low temp with some thought.
 
I think I found a small 120v kiln. I am thinking a 4 inch diameter tube 18 inches tall, any idea how many pounds of salt I should order?
 
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