Why Kamakura = best swords ever??

[Toryu2020]

Ubu, zaimei, dated 1335, 87.7 cm I'd say that's a fully realized Nanboku-cho shape at a time we'd call "Early Nanboku-cho"...

-t

[ROKUJURO]

8 hours ago, Jacques D. said:

 

Yes but the future hada is mainly determined during the making of the kit (tsumiwakashi), it is the assembly of pieces of different hardness that will give the hada, if you fold and refold a totally homogeneous steel you will not see any hada. 

Jacques,

I am sorry, but this is dead wrong. Are you referring to the (wrong) theory that Damascus steel consists of layers of different hardness? This is certainly also not the case in Japanese blades.

What we see as HADA are in fact the welding seams of the repeated folding and fire-welding, as I have described before. Usually, KAWA-GANE is not combined of different steels as you can read and see in many publications and videos. 

[DoTanuki yokai]

23 hours ago, ROKUJURO said:

HADA has ONLY to do with the work of the smith. It is a result of the repeated folding and fire-welding of the billet.

The pattern of the folding and welding won’t change but what we see is more then only the layers. 
 

http://www.ksky.ne.jp/~sumie99/nashiji.html
 

http://www.ksky.ne.jp/~sumie99/jinie.html

 

I did not had the time to check in the Modern swords and sword smith book yet. But from memory I can remember  that they tried different homemade Tamahagane and the Opinions where broad. Some say it’s the material some say it’s the quench and ofc some say it depends on both and more. 

[mas4t0]

I've attached a photo to provide some further clarity to what Jean described above.

 

The knife at the top is clad in folded iron which was polished on natural stones and the bottom knife is clad in pattern-welded layered "damascus" steel which was etched to bring out the pattern.

 

The visual effect is very different (for the reasons described by Jean).

 

[ROKUJURO]

There is no magic in all these steel formations for us in the West. We can explain all features.

 

This says it all: "....Nashiji-hada may come from proper material and hardening work..." if you understand it.

When we discuss the subject, HADA should not be mixed up with NIE or NIOI which are martensite structures.
 

[Nicolas Maestre]

Wow, thanks a lot everyone for your thoughts on this topic. I just love this board 😁. Fantastic reading!

 

What I got from everyone's inputs is that the words "best" or "quality", when referring to Kamakura blades, are used in the aesthetic sense. And if considered this way, I understand that indeed, there is a general consensus that Kamakura blades remain pretty much untouched to this day. Which I find absolutely fascinating. 

 

On 9/2/2022 at 5:38 AM, Ken-Hawaii said:

But having one in hand to study, is the best way to decide for yourself why they are so superior. I have a few Kamakura & Nanbokucho blades that I have studied, in great detail, for several years. But just last night, I picked up my favorite, & noticed a major feature that I would have sworm wasn't there! I think Kirill put it best: "Best mid-Kamakura steel has a unique appearance. Its like a smoke, ever changing at every possible angle, very bright yet at the same time obscure. You don't really see it ever again at later times. No one can replicate this period's utsuri or even the hamon. Its just very different."

 

Thanks, that sums it up I think. That's an awesome story by the way! Shows how subtle and complex this whole thing seems to be... Well, maybe one day I will have the chance to handle and study such blades in person... Sadly I don't know anyone who's into Nihonto in the area where I live (near Angers, in western France).

 

13 hours ago, Jussi Ekholm said:

Of course still you cannot cut a warrior in full armor in half with a sword regardless if it was one of various low level Sukesada or the Masamune making the sword.

 

It's funny because a low level Sukesada is precisely what I just bought as my first Nihonto 😁 (see here and here).

I agree with your statement btw!

[ROKUJURO]

On 9/3/2022 at 9:45 AM, Jacques D. said:

......it is necessary to take into account the mass effect; the more the tatara is big, the more there is matter in the tatara, the more the temperature will be high and the rate of carbon will be higher. When the other components they remain present but their quantity is negligible and are not to be confused with the impurities which will be eliminated by the folding process. A too high carbon content is bad because it makes the quenched steel too brittle. This is why in Shinshinto it is folded more to decarbonize it and it's why we obtain the famous muji hada

 

Jacques,

 

where did you gather these information? The temperature in a bloomery furnace (may that be called TATARA or other) depends on the air supply, nothing else (provided there isn't a lack of fuel/charcoal).

From the results of analyses we know that the Celtic bloomery kilns were run at temperatures of 1.250 to 1.300°C. This was enough to produce good and relatively pure iron and a small amount of steel.

Modern TATARA (like the NITTOHO) are using much more air so the temperature is slightly higher (up to 1.350°C). This results in a higher steel output compared to (low-carbon) iron, but as a side-effect, also a good amount of cast iron is produced near the vents. This cast iron is of no use in forging and would have to be processed (de-carbonized) to make it usable.

Some smiths use this cast iron to increase the carbon content of their steel.

Generally, the carbon content in the HA area of swords is found to be between 0.5 and 0.7%. When a blade breaks, many factors play a role besides the carbon content.

 

[Jacques D.]

6 hours ago, ROKUJURO said:

Jacques,

I am sorry, but this is dead wrong. Are you referring to the (wrong) theory that Damascus steel consists of layers of different hardness? This is certainly also not the case in Japanese blades.

What we see as HADA are in fact the welding seams of the repeated folding and fire-welding, as I have described before. Usually, KAWA-GANE is not combined of different steels as you can read and see in many publications and videos. 

 

 

[ROKUJURO]

Jacques,

thank you. I know this video of course, and it does not support your theory at all.

[Jacques D.]

Jean stop please each piece of steel ha a little difference in carbon content

 

 

 

[ROKUJURO]

Jacques,

these theories are long outdated!

Please read about carbon diffusion/migration in steel.

[Jacques D.]

Jean; 

Sure and earth is flat.  

 

Would you please tell the physicist that I am how the bonding between the iron atoms and the carbon atom is done? If you don't understand that the material is more important than the hammer blow, I can't help you. try to draw a hada by folding  pure copper => no visible hada. On the other hand you will get one by mixing pure copper with shakudo... It's the same thing for steel. One shade of steel and the hada will never be visible. Don't forget that it is the polisher who reveals the hada because the stone abrades the softer steel a little more than the harder one.
By the way, how do you get an O-hada like Norishige's or a Ray hada? By mixing hard steel and medium soft steel. 

 

 

[ROKUJURO]

Jacques,

I am a bladesmith and experimental archaeologist, and I work with this subject and have some experience.

I have studied Japanese forging techniques and made research in this field.

It would be sad if this discussion went on the dogmatic side instead of the scientific side which I am interested in.

I know that you are very knowledgeable as far as blades are concerned, and my field is, how they were made.

So I would like to leave this subject open and recommend reading about Damascus steel, fire-welding and, again, carbon diffusion/migration in steel.

Kind regards,

Jean

[Alex A]

Interesting video's 

 

Part1 plus

Part2 At 1.55 "Billets that have slightly different carbon content will form layers that will contrast when polished. Plus a variety of forging techniques that can be employed to create subtle changes"

 

 

 

 

 

[Baba Yaga]

4 hours ago, ROKUJURO said:

It would be sad if this discussion went on the dogmatic side instead of the scientific side which I am interested in.

 

It's easier to believe (opinion) then believe 20th century science. It fits a romantic narrative people want to believe.  You can't argue opinion    

[Jacques D.]

10 hours ago, ROKUJURO said:

Jacques,

I am a bladesmith and experimental archaeologist, and I work with this subject and have some experience.

I have studied Japanese forging techniques and made research in this field.


Jean

Why don't you answer my question? 
What does the carbon do in the process? It breaks the iron oxide molecule to extract the oxygen and forms CO2. The remaining carbon atoms are intercalated between iron atoms, in a totally random way, so that you cannot obtain a steel with a homogeneous carbon content by ore reduction, it can only be obtained by decarbonation of the cast iron.

 

The craft of Japanese sword page 66

[Alex A]

You see lots of swords made with a more refined steel/equal steel. Folk often describe them as looking bland or boring.

 

The guy in the vid i linked described features in older blades that you lose once you fold and work the steel many times. Part of the reason you wont see such features in a tight Shinshinto Ko-itame, some folk think thats boring too.

 

[mas4t0]

11 hours ago, Alex A said:

You see lots of swords made with a more refined steel/equal steel. Folk often describe them as looking bland or boring.

 

The guy in the vid i linked described features in older blades that you lose once you fold and work the steel many times. Part of the reason you wont see such features in a tight Shinshinto Ko-itame, some folk think thats boring too.

 

 

I have a sword from Walter Sorrels (the Bladesmith who's videos were linked above). The blade has been traditionally polished, but the visible appearance of the hada is (very) noticeably different to what you'd see on Nihonto or what you'd see on a folded iron-clad Japanese knife. You can see that it's composed of dissimilar layers.

 

The hada that we're used to on Nihonto looks a lot more like alloy banding than layers of different materials.

 

Here's a photo of a monosteel blade (Togashi Blue #2) showing alloy banding where no folding or pattern welding has taken place.

 

 

There's a few factors which determine alloy banding and the smith can quite well control it (even without folding the metal).

 

As I understand it, alloy banding can occur whenever there's presence of carbide forming alloying elements (Cr, V, W, Mo, etc), which brings me back to the idea of a material composition (i.e. chemical) difference as the underlying cause of the different appearance of hada in different eras (beyond the control of the smith) discussed earlier.

 

I assume that the hada is visible due to differences in hardness, which is brought out when the blade is polished. I don't believe though that those hardness differences are (in the case of Nihonto) due to dissimilar materials, but rather I would guess they're due to differences in carbide formation (as seen in alloy banding) within the folded steel.

 

This thread (regarding alloy banding) over at bladesmiths-forum might be of interest to some:

 

https://www.bladesmithsforum.com/index.php?/topic/2703-understanding-alloy-banding/

[Alex A]

Aye Mark, i get what your saying.

 

He does mention a “variety of techniques to create subtle changes” but eludes to give us the details.

 

Unknown territory for me, but interesting trying to understand.

[ROKUJURO]

Mark,

thank you for that link! There is a tiny mistake in that thread: Daniel Gentile should have used the correct term "hypo-eutectoid steel". Plain eutectoid steel contains 0.78% C.

I have been mentioning carbon diffusion a few times for a reason. As we know today, carbon migrates in steel at temperatures above 900°C. The higher the temperature and the longer the time the steel is exposed to high temperatures, the more carbon can penetrate (in the case of carbon-free iron) into the material. In the case of low-alloy high-carbon steels (as in TAMAHAGANE) with different carbon content, carbon will migrate from places with high carbon content to those with low content, until it comes to a balance.

Carbon diffusion goes fast at fire-welding temperature, and when you watch a Japanese swordsmith heating up the steel until a lot of sparks are coming out of the billet, you know it has about 1.300°C or even a bit more.

This is done to equalize the carbon content in the billet. With 10 to 12 foldings for KAWA GANE, the swordsmith knows from experience that his steel has about 0.7% of carbon throughout and is well homogeneized.

Let's play a bit with numbers: Assuming the smith did (only) 10 foldings, and his billet has a final thickness of 6 cm, a single layer of steel in it has a thickness of 0,06 mm. That corresponds roughly to the thickness of a European woman's hair.

 

Carbon migration goes fast from one thin layer to another under the condition of fire-welding! Even assuming that the carbon content could be slightly different from one layer to another, a complete homogeneization of the billet will be the result. Watching some YouTube videos about Japanese swordsmithing will teach you that the smith carefully chooses his TAMAHAGANE for even carbon content. So there is even a pre-selection of the raw material.

There is a trick to prevent carbon diffusion by inserting a pure nickel layer in the billet, but as we all know, this is not done in sword forging.

I will mention that less folding with the result of thicker layers can reduce the carbon diffusion. If a smith chooses to use thick steel sheets with considerably different carbon content in the billet, it may well be that the finished blade shows a structured surface with small differences in the steel colour. This can often be seen in early European blades. But that is not done in Japanese sword forging.

 

The legend that Viking swords (and even today's Damascus steel which is very different from Viking swords and 'true' Damascus made in India and Persia a few hundred years ago) are made from hard and soft steel and thus combine good cutting abilities with flexibility will persist as it seems to be logical. But it is only logical to people who don't understand metallurgy. 

Concerning carbide formation, we have an eutectoid steel in a Japanese blade which means that the full carbon content is dissolved in the steel matrix. There are no clusters of carbides as in high-alloy steel. But due to the special technique of heating and quenching, martensite crystals of differing sizes can form in the steel which we see as NIE or NIOI.    

[mas4t0]

29 minutes ago, ROKUJURO said:

Mark,

thank you for that link! There is a tiny mistake in that thread: Daniel Gentile should have used the correct term "hypo-eutectoid steel". Plain eutectoid steel contains 0.78% C.

I have been mentioning carbon diffusion a few times for a reason. As we know today, carbon migrates in steel at temperatures above 900°C. The higher the temperature and the longer the time the steel is exposed to high temperatures, the more carbon can penetrate (in the case of carbon-free iron) into the material. In the case of low-alloy high-carbon steels (as in TAMAHAGANE) with different carbon content, carbon will migrate from places with high carbon content to those with low content, until it comes to a balance.

Carbon diffusion goes fast at fire-welding temperature, and when you watch a Japanese swordsmith heating up the steel until a lot of sparks are coming out of the billet, you know it has about 1.300°C or even a bit more.

This is done to equalize the carbon content in the billet. With 10 to 12 foldings for KAWA GANE, the swordsmith knows from experience that his steel has about 0.7% of carbon throughout and is well homogeneized.

Let's play a bit with numbers: Assuming the smith did (only) 10 foldings, and his billet has a final thickness of 6 cm, a single layer of steel in it has a thickness of 0,06 mm. That corresponds roughly to the thickness of a European woman's hair.

 

Carbon migration goes fast from one thin layer to another under the condition of fire-welding! Even assuming that the carbon content could be slightly different from one layer to another, a complete homogeneization of the billet will be the result. Watching some YouTube videos about Japanese swordsmithing will teach you that the smith carefully chooses his TAMAHAGANE for even carbon content. So there is even a pre-selection of the raw material.

There is a trick to prevent carbon diffusion by inserting a pure nickel layer in the billet, but as we all know, this is not done in sword forging.

I will mention that less folding with the result of thicker layers can reduce the carbon diffusion. If a smith chooses to use thick steel sheets with considerably different carbon content in the billet, it may well be that the finished blade shows a structured surface with small differences in the steel colour. This can often be seen in early European blades. But that is not done in Japanese sword forging.

 

The legend that Viking swords (and even today's Damascus steel which is very different from Viking swords and 'true' Damascus made in India and Persia a few hundred years ago) are made from hard and soft steel and thus combine good cutting abilities with flexibility will persist as it seems to be logical. But it is only logical to people who don't understand metallurgy. 

Concerning carbide formation, we have an eutectoid steel in a Japanese blade which means that the full carbon content is dissolved in the steel matrix. There are no clusters of carbides as in high-alloy steel. But due to the special technique of heating and quenching, martensite crystals of differing sizes can form in the steel which we see as NIE or NIOI.    

 

Thank you Jean for clarifying and elaborating.

 

I had guessed that the small amounts of Molybdenum and Vanadium would be drawn to the surface and thereby concentrated at the welds - with high enough concentration to form carbides along the weld lines.

 

As that isn't the case, what would you guess we're actually seeing?

 

Clearly we're seeing the welds, but I'd very much appreciate your insight as to what's going on metallurgically to create the visible contrast.

[Alex A]

Always hate to quote wiki for some reason, but this is how i have always thought Japanese swords were constructed.

 

Somewhere in this thread some differing opinions have me a little lost.

https://en.wikipedia.org/wiki/Japanese_swordsmithing

 

And again " the different layers of steel are made visible during the polishing because of one or both of two reasons: 1) the layers have a variation in carbon content"..........

 

And a new one for me "2) they have variation in the content of slag inclusions".

 

Forging[edit]

 

Forge scenes, print from a book from the Edo period (1603–1867), Museum of Ethnography of Neuchâtel.

 

Blacksmith scene, print from an Edo period book, Museum of Ethnography of Neuchâtel.

The steel bloom, or kera, that is produced in the tatara contains steel that varies greatly in carbon content, ranging from wrought iron to pig iron. Three types of steel are chosen for the blade; a very low carbon steel called hocho-tetsu is used for the core of the blade (shingane). The high carbon steel (tamahagane), and the remelted pig iron (cast iron or nabe-gane),^[11] are combined to form the outer skin of the blade (kawagane).^[12][13][14] Only about 1/3 of the kera produces steel that is suitable for sword production.^[15]

[mas4t0]

1 hour ago, Alex A said:

Always hate to quote wiki for some reason, but this is how i have always thought Japanese swords were constructed.

 

Somewhere in this thread some differing opinions have me a little lost.

https://en.wikipedia.org/wiki/Japanese_swordsmithing

 

Forging[edit]

 

Forge scenes, print from a book from the Edo period (1603–1867), Museum of Ethnography of Neuchâtel.

 

Blacksmith scene, print from an Edo period book, Museum of Ethnography of Neuchâtel.

The steel bloom, or kera, that is produced in the tatara contains steel that varies greatly in carbon content, ranging from wrought iron to pig iron. Three types of steel are chosen for the blade; a very low carbon steel called hocho-tetsu is used for the core of the blade (shingane). The high carbon steel (tamahagane), and the remelted pig iron (cast iron or nabe-gane),^[11] are combined to form the outer skin of the blade (kawagane).^[12][13][14] Only about 1/3 of the kera produces steel that is suitable for sword production.^[15]

 

The material first needs to be refined. The section quoted is discussing lamination of material after it's been refined by folding.

 

The discussion is currently focused on the hada left by folding the material in order to refine it.

 

Quote

 

Once the steel had been refined, it can be used in the same way as mill steel.

 

And again " the different layers of steel are made visible during the polishing because of one or both of two reasons: 1) the layers have a variation in carbon content"..........

 

And a new one for me " 2) they have variation in the content of slag inclusions.

 

 

I doubt both of those reasons, due to 1) carbon migration (as described by Jean) and 2) the slag inclusions are removed through the refining process (i.e. folding), which also homogenises the material.

 

The material for the respective layers (of lamination) is kept separate until the final billet is assembled and drawn out.

[Alex A]

Im not talking about refining the materials, im referring to the steel ready to make the blade.

 

Had folk saying the outer skin of the blade is just one type of steel whilst someone else said its 2

 

What is it ?

[mas4t0]

11 minutes ago, Alex A said:

Im not talking about refining the materials, im referring to the steel ready to make the blade.

 

Had folk saying the outer skin of the blade is just one type of steel whilst someone else said its 2

 

What is it ?

 

1, unless the blade is laminated in a way which leaves both Kawagane and Hagane exposed, such as Honsanmai.

 

But in that case you're seeing two distinct materials side by side (as with a san-mai blade) rather than blended and pattern welded together (as you might see on a traditional Chinese sword).

[Alex A]

 2   

 

Might be refined and ready to go

 

again

 

"The high carbon steel (tamahagane), and the remelted pig iron (cast iron or nabe-gane),[11] are combined to form the outer skin"

 

 

Otherwise, as Jacques pointed out, no contrast in hada.

 

 

 

 

[Alex A]

14 minutes ago, mas4t0 said:

 

1, unless the blade is laminated in a way which leaves both Kawagane and Hagane exposed, such as Honsanmai.

 

But in that case you're seeing two distinct materials side by side (as with a san-mai blade) rather than blended and pattern welded together (as you might see on a traditional Chinese sword).

 

Yes, but they are folded, end result.................... hada

[mas4t0]

49 minutes ago, Alex A said:

 2   

 

Might be refined and ready to go

 

again

 

"The high carbon steel (tamahagane), and the remelted pig iron (cast iron or nabe-gane),[11] are combined to form the outer skin"

 

 

Otherwise, as Jacques pointed out, no contrast in hada.

 

 

 

 

 

42 minutes ago, Alex A said:

 

Yes, but they are folded, end result.................... hada

 

Of course the metal is folded as part of the refining process, but due to that process the carbon content has been homogenised throughout a piece of material. These are then laminated together to form the final billet.

 

Hada does not require dissimilar alloys. The cladding on this knife is folded (impure) iron, which began as a single piece of iron before being folded on itself and used to clad the high carbon core steel; the pattern is revealed by polishing on natural stones.

 

[Alex A]

Yes, totally agree hada does not require dissimilar alloys, i get that.

 

Also, i understand now about how carbon gets levelled out during the process, so to speak.

 

Though, traditional Japanese blades do combine 2 materials for the outer skin and that makes for greater contrast.

 

I suppose you could ask yourself. If a smith was to make 2 swords, one with 2 and the other with just the 1 steel type in the skin of the sword , would they look the same after polish ?, doubt it.

 

Now someone tell me why Kamakura blades were more pretty 

 

 

 

[ROKUJURO]

Mark is correct and has understood the process.

The idea that HADA will only show if made of two (or more) components may have derived from the modern Damascus principle: Two (or more) steel components of different composition are fire-welded together, and the final process after forging, heat-treament and grinding/polishing is an acid treatment. The metal layers will be attacked differently by the acid (or iron chloride solution) and show different colour - one steel may become black (manganese steel), another one does not react so much with the acid and remains silver (nickel-alloyed steel). This results in strongly contrasting pattern in the surface of the blade.

Long Japanese blades are not made this way. Here, the principle is a composite inner structure (KITAE) of two or more components (I don't mention the TANTO which are made of mono-steel), and each of these is made of thoroughly refined (= homogenized) steel.

The principle behind that is that you can exoect predictable properties only from perfectly homogenized material. This explains also, why many blades (often KAZU UCHI MONO) failed in combat which were made hastily by lesser smiths to equip troops in a less costly way.

 

Core steel (SHIN-TETSU) with lower carbon content was usually folded 12 to 15 times, sometimes even more. This lowered the carbon content, and in combination with KAWA-GANE (roughly 0,5 - 0,7% C) allowed for a flexible blade with very good cutting properties.

 

So please leave the idea beside that HADA in KAMAKURA JIDAI shows up because there were two steel components. The JIGANE was pefectly homogeneous steel!

Much later in Japanese history we see blades with stronger contrast of different materials in the JIGANE. This was intentionally made and the result of combining steels with alloying components (NANBAN TETSU and others).