How effective would a sword be without a hamon?

[mas4t0]

I think in many ways that the historical constraints are still relevant and the effects are still visible. The qualities of the available blades directly influenced the technique of the trades that relied on these blades as tools.

 

The western approach to breaking down poultry for instance is entirely different to the Japanese approach. The knives have different shapes, different geometry, along with different levels of sharpness and durability. Today this is optional, but the two different approaches and blade styles are clearly optimisations to what was achievable, and the techniques developed have been handed down to the present day.

 

The western approach relied more on brute force and durability of the blade (often chopping through bones) while the Japanese approach relied on sharpness and precision to cut the connective tissue and separate at the joints without breaking any bones. One is more similar to a hand axe while the other is closer to a scalpel. All my vegetable knives are Japanese, but I use only western style butchery knives as I lack the skill that the Japanese knives require.

[PNSSHOGUN]

There was testing done during the development of the Koa Isshin Mantetsu, here is a table of different Jidai and Tosho and their respective edge and spine hardness from Ohmura's site: http://ohmura-study.net/998.html

 

 

[mas4t0]

Thank you John.

 

Are there any units for the table? I took a look through the site, but down see any reference to the units.

 

It can't be HRC though as steel tops out at ~65HRC and we have numbers here >80.

[PNSSHOGUN]

Perhaps Vickers or a different Rockwell table. Or it could very well be the Professors own system for Japanese swords specifically.

[Apercus]

Cyril Stanly Smith who was one of the pioneers in metallurgical examination of steels cut Japanese blade sections to reveal different type constructions. One type examined was a san-mai blade but the outer layers were of a medium carbon content rather than iron. With at least 45 points of carbon (I.e. 0.45%) a hamon would be produced. It has been my experience that banite forms more readily in a medium carbon content steel with a differential application of heat. I believe banite is what we usually recognize as utsuri. It’s a shame there hasn’t been more study in this area. All we can do is speculate over the little bit of data available. Just my two cents worth of speculation.

Shannon Hogg

[mas4t0]

I'd be curious when the analysis was done, just because Bainite was originally described as being similar in appearance to tempered martensite.

 

I seem to recall some analysis done on Nihonto a little over a decade ago at my alma mater and I don't recall any mention of Bainite.

[Apercus]

I don’t have anything definitive for you. The samples I examined 25 years ago with SEM led me to believe the areas that displayed utsuri matched the profile of banite. (Fine dispersal if smaller crystalline structures). They certainly were formed at a lower temperature than the martensite because of differential heating. I only stated that I was speculating that much of what we identify as utsuri is actually bainite. Yoshindo Yoshihara noted in his book The Craft of the Japanese Sword, that utsuri was formed at a lower temperature than martensite. That temperature corresponds to the temperature that banite forms. I guess someone will need to make samples and do some research to definitively prove the point. I’m not in a position to do any of that now. Howard Clark claims his blades have a hardened edge of banite which is almost as hard as martensite but which does not have the brittleness of martensite. Bainite is known to have greater toughness than martensite. Perhaps he might be coaxed to share some of his work.

Shannon Hogg

[PNSSHOGUN]

I was under the impression bainite was achieved by long tempering at a strictly controlled temperature, but that may have been usable bainite in a sword.

[mas4t0]

  On 2/11/2020 at 9:05 PM, PNSSHOGUN said:

I was under the impression bainite was achieved by long tempering at a strictly controlled temperature, but that may have been usable bainite in a sword.

Just to add some more info, you'd usually produce Bainite by Austempering, which is the process described. The key part is the quench. It's usually done in a molten salt bath and then held for a while to allow Bainite transformation.

[mas4t0]

  On 2/11/2020 at 2:41 PM, Apercus said:

I don’t have anything definitive for you. The samples I examined 25 years ago with SEM led me to believe the areas that displayed utsuri matched the profile of banite. (Fine dispersal if smaller crystalline structures). They certainly were formed at a lower temperature than the martensite because of differential heating. I only stated that I was speculating that much of what we identify as utsuri is actually bainite. Yoshindo Yoshihara noted in his book The Craft of the Japanese Sword, that utsuri was formed at a lower temperature than martensite. That temperature corresponds to the temperature that banite forms. I guess someone will need to make samples and do some research to definitively prove the point. I’m not in a position to do any of that now. Howard Clark claims his blades have a hardened edge of banite which is almost as hard as martensite but which does not have the brittleness of martensite. Bainite is known to have greater toughness than martensite. Perhaps he might be coaxed to share some of his work.

Shannon Hogg

Thank you for elaborating, it's an interesting idea.

 

Howard uses salt baths so I'm sure he's using a variation of the Austempering process.