HT question for Kevin Cashen

[Plain ol Bill]

Hi Kevin - hopefully you will see this post. I am working w/ my new salt pots and loving doing my HT this way. My question for you is - when working w/ 1084 & 15N20 damascus how long would you normally leave the knife in solution? I did ten blades this morning and I let the controller cycle through a couple of times and then removed the blade after putting it into solution. Does this sound like a long enough soak to you?
Thanks for any help Kevin -

 

[Kevin R. Cashen]

Bill, I hope you don't mind if I invite and encourage other folks to give input as well, it would be in your best interest to get a nice cross section of opinions and not limit yourself to my viewpoint while you have a resource such as this board at your disposal. If you still wish my thoughts alone, feel free to contact me anytime at kevin@cashenblades.com

There are no one recipe fits all for heat treating even when the alloys are the same since the prior heat treatments will have a profound effect on things such as soak times. 1084/15n20 is a mix that should take the least amount of effort to get into solution so soak times will not be near as critical as something with more alloying. Be certain to watch for the rebound of the temperature in the salts, since any soaking does not begin until the rebound is complete. Be certain your salts have levels off at the austenitizing temperature of your choosing and then introduce the blade. The controller should begin to read a lowering temperature down to around 20 degrees lower and then start climbing slowly back up. When the reading is back your original temperature I would do at least a 4 minute soak before quenching.

Even the guys who do things entirely differently than I do will quickly tell you the importance of testing, I wholeheartedly agree even though I may dissagree with what those tests should be. The best way to zero in on your soak time is to make up some small samples from the same steel the blade is made from, stamp numbers on them corresponding with increasing minutes and then put them all in the salt at once. Quench one at 2 minute soak another at 4 minutes, then 6 and 10. Take Rockwell readings off from these and find the first number that maxes out in hardness. Then break the samples and examine the grain. This will be worth volumes more than any monkeying around you could do with the final knife, and without the waste of experimenting with a perfectly good blade.

 

[John Frankl]

Bill,

Congrats on the salts. Any photos/info?

Thanks,

John

 

[Plain ol Bill]

Kevin I want to take a moment here and let you know that I sincerely appreciate your taking the time to share your knowledge with all of us that frequent this board. THANK YOU.
Now with that said I will take your advice to heart and do some testing using the same materials. Like you reccomend that will allow me to zero in on a soak time. I can tell the material is definitly harder than when i was HT,ing in the forge already.
Another big plus, and the primary reason I went to salts, is that now I can finish a blade to a much higher degree with the material still in a soft state. Hand sanding sucks - and it is a LOT easier to do on soft material.
John - I will try to get a couple of pics in the next few days and post them up. Of course I used stainless - I like shiny things sort of like an old crow does. I used two venturi burners on the set up and they work really well. The controller is set to turn off at 1550 and relight at 1545. I notice the temp will coast to 1560 after the burners shut off. On the other end when it relights at 1545 it will still coast down to 1541 before it heads up again. I am happy with these numbers so far.

 

[Kevin R. Cashen]

Please do share some pics if you can, my salt baths are never done evolving and I always welcome the opportunity to learn from other folks experiences. I would like to build some new venturi fired units when I get time, myself. I don't push in selling the salt baths as hard as I used to, since I came to the realization that they just may not be everybody’s cup of tea and can take folks who are into more carefree traditional bladesmithing in the opposite direction than what they may want to go. That being said, I wouldn't do without my salts again. What you said about the finishing is very high on my reasons to love the salts. 32 HRC steel finishes out much quicker by hand than 60HRC steel does One can get the final dimensions as close as you like and not worry about decarb or any other nasties. The straightness of the blade from the quench is only limited by your own eyesight, and that head start on the tempering does some very nice things for toughness.

As for the samples, I run about a dozen little steel pieces through the salts every time I have them fired up for any reason. There is always something new to test for or learn and I simply cannot ignore any opportunity to do so. Anymore I spend almost as much time testing as I do making knives and testing without accuracy and consistent repeatability is worthless, so for me the salts are a must.