Honyaki Double Hamon explenation??

[SwissKnifeCollector]

Hello guys

I just started to polish my bunka I am working on recently in our shop and noticed that after the quench a double hamon formed. I have never seen hat before. 850℃ ifor the heat treatment, oil quench , after that 180℃ for 2h in the Oven. Hardness measured around 64HRC.

Has anybody an explenation for that?

 

[JPAU]

I’m no expert but there seems to be precedent for this. Have a look at the Togashi x Yohei on BsT. One linear Hamon and one wavy, or so it appears to me

 

[MowgFace]

Munetoshi Honyaki sometimes have them too

https://www.japanesenaturalstones.com/munetoshi-honyaki-gyuto-210mm-special-1/

 

[RDalman]

Is the upper your clay application line? If so that's your explanation. You didn't grind away surface decarb you had through the clay. And the actual hamon positioned lower than your clay.

 

[Enso Forge]

Hello guys

I just started to polish my bunka I am working on recently in our shop and noticed that after the quench a double hamon formed. I have never seen hat before. 850℃ ifor the heat treatment, oil quench , after that 180℃ for 2h in the Oven. Hardness measured around 64HRC.

Has anybody an explenation for that?

View attachment 306085

My guess is that’s it’s utsuri from where the clay was applied. What happens is during the quenching process the temperature right at the line is slightly lower than the critical temperature needed to form martensite. The cutting edge however is still above the critical temperature and hardens properly forming a hamon, while the area in between the clay and hamon is still softer.

 

[Veitchii]

My guess is that’s it’s utsuri from where the clay was applied. What happens is during the quenching process the temperature right at the line is slightly lower than the critical temperature needed to form martensite. The cutting edge however is still above the critical temperature and hardens properly forming a hamon, while the area in between the clay and hamon is still softer.

My immediate thought too. You know, it's said that Japanese swords made within the last 400 years rarely show utsuri, but I sometimes see skilled knifemakers produce it intentionally on forums. I'm not a maker myself (yet), but I've been interested in honyaki knives and hamons for a while, and I'd like to know more about how the clay was applied here because I think it looks sweet. What kind of steel is it made of?