Why quench them in liquid nitrogen before they go into temper cycles? These came out at 320 degrees below zero (F). Bill Harsey (who just recently finished his new shop – looks good sir!) advises, “The shop air hits the blades and cools, it’s frozen fog falling from the blades.”
According to Bill Harsey (the designer of the Yarborough Knife and the Neil Roberts Warrior Knife, and a man who has worked with Al Mar, Col. Rex Applegate and Col. Nick Rowe), you quench them in liquid nitrogen because:
- Tool steels harden or soften without changing chemical composition depending on how they are heated and cooled. How they are heated and cooled (times and temps) depends on the alloying elements like carbon, vanadium, chromium and in this case niobium too.
The below names describe some of these phases.
- the deep freezing (cryogenic) step mechanically converts the retained austenite into martinsite and pearlite resulting in higher transverse bend fracture strength (pry bar strength) and better edge holding.
{ 13 comments… read them below or add one }
Bill is pretty well known in the blade community. Come to think of it, I think I have one of his designs somewhere around here (;
Awesome post, loving the technical exposure
To de-science that a little bit, dipping them in Liquid Nitrogen makes them really strong and able to better hold an edge.
…Only if the cryo is followed by a heat cycle…
Bear Honorary CSM 9th Inf. Regiment
Always loved my Al Mar knive(s), (nephew acquired the folder). But then again the man was a genus. His master’s thesis was building a working 2 man submarine. Submariner in me appreciates how hard that has got to be. From something that complex, to the singular beauty of my old SERE.
It appears Bill Harsey and Chris Reeve are the heirs apparent.
Outstanding product and American Made.
Time for me to get a new K-bar.
Ooh-Rah
Need a new folder…some one needed mine more then I did,they Liberated it from me ~><~….So if you have grate folder,i need to pick up another!!!
Benchmade Sabrosa. http://www.benchmade.com/products/790
http://www.benchmade.com/products/2750
Hope you have large hands. It’s pretty big, also comes with a great molle pouch.
If you like blades http://www.angelswordstore.com/index.php?option=com_frontpage&Itemid=1
angelsword uses a similar process for what they call supersteel.
Actually, it was MythBusters who named it not”supersteel”, but “supersword” It chopped up the other blades with ease. That sword was his low-end, the Bright Knight line. They sent the other sword, an Avatar techno-wootz, back to the shop since they couldn’t find any other sword to even test it against.
Daniel Watson, the creator of the techno-wootz, uses a patented ThermaCycle process using both liguid nitrogen and heating chambers. He offers the process for existing blades, tools, firearms, etc.
Yes, the blades are pricey, but they are made to use and cut with in a real-life scenario. There is a lifetime warranty on them, and the heirloom quality of them persuaded me to buy mine.
You are correct.
I will have one, someday.
Thanks for posting the pic of some of my work.
I use three separate progressive temper cycles after the cryogenic step in the heat treat.
These knives are being donated by Spartan Blades and myself to the Special Operations Forces Sniper Competition held on Range 37 in Ft. Bragg, NC., as awards, next week.
Bill Harsey