Salt pot blowout repair

Joined
Mar 26, 2000
Messages
658
A couple of weeks ago I had a high temp salt pot develope a leak just at melting temp. The weld on the bottom cap had a pin hole develope after 4 years of usage. I grabed that hot pot with my forging tongs and lifted it out of the heat. It cooled so fast very little salts actually ran out once it was out of the heat(can't say the same for inside the heating forge) I was not ready to handle the pot of hot semi molton salts and it hardened inside the pot.
Upon examination the outside of the pot showed no heat erosion as it was 304 SS. So I cut the bottom inch of the pot in hope to reuse the pipe section.
The next job was to get 14 inches of hard salts out of a 4 inch ID pipe. Heating it up to melting point 1700F uncontained did not seem very safe. Hammer and chisel was given up after 5 min.
But 5 days in a 5 gal bucket of water disolved all the salt out of the tube. No effort at all.
Now all I have to do is get a better welder than me to weld a cap on it again.:D
 
How are we supposed to have sun in your shop if you go and melt all of your equipment? Gee, maybe you should come visit me and we can play with my 2X42 all week-end! LOL!
 
What is the salt container tube made of? Mine is stainless of some sort and its starting to get thin and scares me. What should I start looking for? I like the idea of a 2-3" tube about 36" deep. How thick of wall?
 
Bruce
My tube was a 20 inch lenght of 304 S/S pipe. I had put a mild steel base cap on it and that has eroded quite a bit along with the weld. It flake away in what looked like big decarb forging flakes. The tube was originally .20 wall thickness and that has not changed. I will now have it caped with some of the .5 inch 304 S/S sheet I have aquired.
Some of the guys I know that use mild steel tube measure the OD of there tube after every HT cycle.
 
My tube is some kind of stainless (it is nonmagnetic) It is flaking away too. How about cast iron? If the forge blast isnt directly on the tube it would last longer. What would be the best material possible?
 
Golly. My total ignorance just hit either a high or low point just now.

Could you please tell me what salt pots are? What they're for? How do you use them?

I'm pretty sure that the phrases "salt pot" or "salt tube" never appeared on any thread I've read on any forum. Sure would appreciate somebody filling me in about this.

Thanks in advance. :)
 
Bugs, Stay away from this subject. The salt pots are why Paul Bos cant treat straight carbon steel anymore. They are not too enviromentally friendly but boy do they heat treat steel (non stainless) nice. I have used mine for only about a year and have almost burnt myself up a couple times. Thats why the girl behind the counter at Arbys asks me if I have just come from a fire. If you put wet steel in the salt it explodes hot molten salt staight up in the air and lands on that small balding spot on the top of your head! If you stick a piece of pipe in too fast, the salt can shoot out the hole in the pipe like a roman candle! If the salt tube gets a hole burnt through hot lava runs all over your berkenstocks and flames come up your leg! Stay away! Stay far away!
 
Bruce and Bugs
They also do a very good job on all stainless steels if done correctly.
Very economical to make, capable to ht blades that do not require temp ramping very quickly. Just a few of the good points.
But as Bruce did say Very Dangerous if used incorectly, I have seen a few salt stippled ceilings. So fare in 4 years I have been major catastrofy free.
 
Thanks for the warnings, Bruce. Not really necessary as I haven't even contemplated becoming a maker. Have zero/zip/zilch mechanical aptitude or ability. I may someday attack a kit or two, or maybe try to replace scales, but that will be all. In my military tests, I am subnormal in both mechanical aptitude and spatial concepts. Seems likely it would be impossible for me to make symmetrical scales.

Edit: I did a search and found Don Fogg's page with enough info to satisfy my basic questions. Guess the only one(s) left I didn't ask below. Mr. Fogg wears a full face shield when he's using his salt pot, plus other protection. I'm very curious about why Paul Bos cannot use salt pots any longer, or at least with carbon steels. It tends to make me guess that there are fumes given off by the liquid salts when superheated, or by the chemical interaction of the steel and it's alloy contents when the steel is in the salt. Did Paul Bos get poisoned, or super sensitive to such fumes?

So, I take it that salt pots are some sort of containers full of some chloride or another that are used in heat treating steel, primarily carbon steels?

Are they covered except when you insert your steel? Would it be possible to have several fine mesh screen covers that could have a hole in them for the type of steel item you are inserting, but that would contain a majority of the "exploding" salts which occur when the steel first meets the salts? -- except when inserting pipe? Kind of like a splash screen skillet cover to use when frying with very hot grease?

Are they better than ovens and torch heating? Less expensive? More expensive? What are the rough dimensions of salt pots? Do different chlorides function differently, or can one basic mixture be used for all steels? It sounds like they are extremely dangerous. What advantage do they offer to offset that danger?

Sorry, I'll quit asking questions. Like I said in my first post, I had just never heard of them. I'll do a search or two, and see if I can find out more about them.

Again, I appreciate your responses. Sorry am a bit slow getting back to them. I understand how everything seems to hit that balding spot. Mine isn't really huge yet, but everything seems to hit it fair and square.
 
Fellows, I have not had any experience with salt pots as you are using them but I have had lots of experience with making caustic for cooking wood chips in. Very ,very strong stuff that will chemical produce first degree burns in little contact time on your skin. All of the piping and vessels is made of 316s.s. Anyway I'm sure if you can obtain 316 s.s. you will never again experience a problem. Make sure that if you get a cap welded on that the person uses the correct type of rod and you will end up with a many life times container. Frank.
 
Frank, Thanks for the tip on the 316 ss.

Bugs there is some advantages. There is zero scale to grind off because no oxidation. The blade is in liquid the entire time of heating and then goes into liquid tempering salts. They can be straightened easy while tempering too. I use only the barrium cloride (liquid heat) but will soon get the tempering salts. A pyrometer should be used so overheating is eleminated. The salt can be heated with a propane set-up and fine tuned while watching the digital reading to maintain the correct temps. The low heat tempering tube could be electric with a thermostat although I havent made mine. Frank says 316 stainless will give us no burn-out trouble. Dont over-size the tanks because warm-up is slow and expensive to fill a too big tube.

They dont seem to give off fumes but I use mine outside anyway. Paul Bos didnt tell me anout any health problems. Disposing of the salts is the problem Ive heard. I do use a loose fitting cover while heating the salt because it could burp and shoot out some hot liquid until fully hot. There is no reason to insert a pipe. I did that but no more. They are not needed for edge quenching but are worth the trouble if you do alot of full hardening carbon steels and damascus. Damascus doesnt always etch nicely if it is edge quenched but looks best fully hardened. Fully hard 52100 sure shines nice. Do a search on "martempering" for more info than I can give. My finger is getting tired of typeing.
 
By the way Bruce as you may suspect the 316 s.s. is very very resistant to warping from heat. I'm sure even 1/8 wall thickness would do fine for your application and of course allow for easier heating. I really enjoy your tutorials and knives Bruce!! I'm sure this will do it right for you. By the way it is terrible suff to work with. Frank.
 
Frank, Thanks for the info on the 316 ss. You dont happen to have a 2 or 3" x 24" pipe lying around do you? Im not sure I would know some if I saw it.
 
sure wish I could help you. I,m retired from the pulp mill for about six years and moved to the souther part of the province where the climate is more moderate.The same stuff is also commonly used in many chemical making and using plants. Frank
 
Thanks for all your help, Bruce. I really appreciate it. Will try the search shortly.

I only mentioned Paul Bos, because I seem to remember someone in this or another thread saying that he "can't" heat treat high carbon steel anymore. I assumed some sort of health problem.
 
Back
Top