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AJ Prime

What IS a hamon???

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Posted (edited)

Ok, so most of us know what one looks like, right? But metallurgically speaking, what is it actually? What is the ghosted line made of? And what makes it visible? 

Is it fundamentally different to a quench line (edge-quench, etc)?

 

Sorry for spewing a bunch of questions out, I'm not sure what the right all encompassing question is. Just looking for a better answer than Wikipedia can give.

 

TIA

AJ

Edited by AJ Prime

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I had to read the Wikipedia page to know what was there so I could properly answer for you.  

The hamon is the visual representation of the blending of hardened steel and unhardened.  More specifically it is where martensite (generally tempered martensite) and pearlite meet.  In this zone you are going to have a mixture of the two phases, and probably a bit of bainite as well.  These phases all etch differently, so the appearance of the hamon is just the mixture of different phases that had a different reaction to the etching.  The etch given is usually very mild, as the difference between these phases of a given alloy are pretty minimal.  The hamon can often be seen without etching, just polishing, because the abrasives, and even just the ambient atmosphere can cause enough of a difference in the reaction of these different phases to be noticeable.  

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To build on this, a true hamon is different from a quench line from edge-quenching because that will result in a very sharp boundary between martensite and pearlite rather than the extended blended zone which is what defines hamon.

This is also why you can't get hamon on deep-hardening steels.  The alloying elements that contribute to depth of hardening (manganese, chromium, molybdenum, etc, but mostly Manganese) remove the ability to have that transitional band of mixed structure.  The manganese must be below around 0.3%, which is why you can't get a good hamon on 1084, which is an otherwise simple alloy.  It has around 0.7% Mn.  

Fine grain also contributes to the width of the transitional area (habuchi in Japanese), which is why W2 with its vanadium content (which helps prevent grain growth) makes such spectacular hamon.  

All the traditional clay does is provide an instant of insulation and an accelerant to the nucleate boiling phase of the quench, both of which contribute to the mixed structure of the habuchi.  If your steel is shallow-hardening enough and your grain is fine enough, you will get hamon without clay, just because the thicker sections of the blade can't harden.  

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Thank you Gentlemen.

I'll be making the attempt later this morning with this 1095 slicer. 

20200612_171629-01.jpeg

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Giday and welcome  @AJ Prime Good to see you join this forum of bladesmiths. A very congenial  group with a great deal of experience and knowledge.

  • Thanks 1

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That's some good claying. If your temp is right, I'm sure you'll get nice stuff going on. Looking forward to see the result.

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