Question for salt bath users

My salt pot is close to being finished and I've got some questions. Do you normalize with the salts ? If so, does the salt drip off ? Also, HT manuals say to soak for one hour for every inch thickness. Does a 1/4" thick blade stay in for 15 minutes ? Thanks.

Hi Dennis!

You've opened the gate for me to do some ranting about heat treating manuals.........but I'll save that for a moment.
Soaking any of the steels we generally consider "forgable" is not a good thing (at least where the quenching heat is concerned) grain size will grow expodentuallly with each passing moment above critical temp. :x I highly recommend taking no more time than it takes to achieve critical temp, and then get the blade out of there!
Now for my rantings........ Heat treat books/manuals are an OK place to START, however as you've mentioned, the information in heat treat manuals/books all seems to be based on achieving the maximum hardness in a one inch cross section of material. The information in these manuals/books does not take into consideration the need for durability (meaning no consideration is given to grain size, which enhances the characteristics we seek in a knife) Therefore it is in our best interest as knifemakers (if we want to produce the best cutting tool we can) to use the information that heat treating manuals provide as a STARTING point. I've had countless encounters with people who live and die by the information in heat treat books..........and frankly they've taken it too far. I have even gone to the point of purchasing some of the makers knives that swear that you must follow the heat treat manual to the letter....... and have found that I have not been impressed with the performance their blades displayed. I'm not jumping at you Dennis, it's just that this is something I have been "preaching" for years, and I'm glad you brought it up! :cool:

OK, I've had my morning flag waving..........I'm much better now! :

You can normalize with salt tanks- the salt forms a thin barrier and becomes solid soon after removing the steel from the pot. In my first few runs I got some decarburization though... To resolve this you need to 'rectify,' the salts by inserting a carbon stirring rod for a few hours every so often. I got a few graphite stirring rods from a jewelry supply house for a few bucks apiece. I suspect that I got the decarb because I didn't do this -before- trying out my new salts. My theory ( and it is just that ) is that the salt wants to absorb carbon... you can feed it stirring rods or you can feed it your knives. The theory goes further that salt starts out kinda hungry... so feed it first.

I did get a few tiny spots of very surface almost scale where the salt ran thin or tiny areas dripped dry. Didn't really affect the final surface too bad but I wonder if it contributed to the decarb.

I have noticed on D Fogg's forum that he normalizes after forging, anneals, grinds and then heat-treats without further normalization. I think if you watch your temps during grinding this should work fine; but it something I am going to try for myself, since I have also heard that grinding can create stresses that normalizing relieves.

The last question on the bottom of the first page of D Fogg's forum addresses this question of procedure, as does:

www.dfoggknives.com/heat_treating2.htm

If this procedure proves workable it would certainly be easier to normalize in the forge than to do it in the salt... providing you have good temp controls on your f0rge.

The info concerning spheroidization on D Fogg in general proves interesting as well... you can do cool stuff with salts!

Have fun... it's a learning curve...

FWIW, Don does most of his shaping by hand, plus I'm sure he forges very close to shape. So I would think that the stresses created during grinding are minimal.

JD

Thanks Jonathan. I think I would prefer to normalize with salts because of the precise temp control. Seems like every time I get close, something else comes up; what is "rectify" salt baths ?Ed, I'm glad the subject came up. Of all the books I've read, none have agreed with each other. It does "fly in the face" of what we've learned, but when they talk about getting alloys into solution I needed to get a bladesmiths view.Thanks.