“Salt bath” or “salt pot” heat treating refers to the use of molten salts for heating steel. Specific salts are used for different temperature ranges, so that they melt under the necessary temperature without certain bad things happening by overheating them. For these experiments I used “Neutral Salt B” by Hubbard-Hall which I purchased from High Temp Tools: https://hightemptools.com/products/high-temperature-salt They list the working range as 1300-1700°F but also says 1700 can only be used for short periods of time. I have also used low temperature salts for austempering which is a totally different use of salt pots; you can read those experiments here. Of course I used a different low temperature salt for those austempering experiments, which you can also buy from High Temp Tools. If you are using molten salts to heat treat stainless or high speed steels you will also need different salts as that would need higher temperatures. These salts are certainly available; salt pot heat treating of high speed steel is actually pretty common, but I don’t know where to buy small amounts of them. If you know a good source let us all know in the comments.
The furnace I used was the EvenHeat Salt Bath 709 which accomodates a 9″ long pot (plus extra that sticks out), though they are also available in larger sizes. There is a control thermocouple within the furnace as well as within the pot itself. So when operating the furnace you heat to the target temperature using the furnace thermocouple first and wait for the salt to melt. Then you insert the second thermocouple into the molten salt and tell the controller to switch modes to the second thermocouple.
You can read the whole thing at KnifeSteelNerds.com
Meanwhile, this remains evergreen…
