Hey everybody!
I recently heat treated a W2 kitchen knife and, to my surprise, it had a "choji" (clove blossom) pattern to the hardening line! There's a Japanese tradition called "Ichimonji" that doesn't use clay and gets this pattern, but people usually sum it up as either inherent to the steel/folding, differential heating, or magic.
I was more or less trying to through harden this thing (so no clay) in my heat treating furnace (a repurposed water heater). Heated up to about 1440° F into about 80° F fast oil (Duratherm 48).
Does anyone have any ideas about how this happens?
I look forward to hearing from you!
-Ethan
Pictures of clove blossom and rough sanded blade:
Ethan, welcome to the auto hamon. With the right combination of blade temp and oil temp it will do it. W2 seems to be the best for it, unless you can get tamahagane. I usually go to 1480 for my W2 blades. So the 1440 may have contributed. Soak time plays a part also. Have fun with it, and show us the knife when you get it done.
Brion
Brion Tomberlin
Anvil Top Custom Knives
ABS Mastersmith
Hey Brion! I'm glad I'm not the only one getting this. I sanded up to 400 today, which both makes it really pop in the right light and frustrating to photograph (see below).
I'm particularly interested to hear anyone's thoughts on why this specific pattern occurs, as opposed to a straight line one would expect if it were just a matter of "edge hot, spine cold".
That's pretty nice.
I do a production line of 1075 belt knives for an outfitter. I always try to fully through-harden them. I get auto hamon all the time. They're much thicker than yours so the result is not nearly as dramatic. You will get that the more shallow hardening the steel is.
Karl B. Andersen
Journeyman Smith
Ethan,
W2 is notorious for doing this. If fact I spent quite a bit of time trying to get W2 blades H/T'ed without a hamon and was unsuccessful. When you quench something as thin as a beveled knife blade from W2 it just naturally wants to form the martensite/pearlite line that way.
Gary
