Tamahagane (玉鋼)

[Laters]

Tamahagane (玉鋼)

 

Been researching this metal for a while and something that keeps comming up is that the majority of the Tamahagane

produced today comes from one place that is the Nittoho Tatara in Okuizumo, Shimane Prefecture. I live in a mining

town and know every mine has metals of varying composition.

 

The question is:

 

If most Japanese Swordsmiths get their steel from one place isn't that going to make future blades somewhat generic?

 

It would be like if every restaurant in the World obtained menu items from only one food supplier.

 

What do You all think about this?

 

Cheers

Edited March 29 by The Forest Ninja

[eternal_newbie]

Basically, yes - there's only so much you can do with the same steel, which is why several smiths make or enrich their own tamahagane (the Akamatsu Taro family being one well-known example - they make theirs from scratch using iron sand they gather themselves).

 

Many smiths and researchers believe there was some mineral or chemical component of the steel used to make the great old works (particularly Soshu) and that this steel running out is what led to the decline of those schools in quality and also drove some of the migration we see in those times. Naturally, it would follow that to truly reproduce those old masterworks, you would need to develop steel of a similar composition as what those old grandmasters used.

 

The research and experimentation continues...

[Lewis B]

Nothing new. Tamahagane production was centralised back in the Edo period (as a means of controlling sword production by the Bakafu), often said to the detriment of the blades produced since then. 

Edited March 29 by Lewis B

[Brian]

Nothing stops smiths adding various elements and other materials while forging it, to get the desired characteristics. It's not like they are forbidden from altering the recipe while they forge. I don't think it's a huge problem.

[Scogg]

I have watched a few videos of modern smiths adding broken pieces of older nihonto to their billet. I imagine this would help provide a level of diversity from one sword to the next in steel composition.

 

Interesting stuff,

-Sam

[John C]

4 hours ago, The Forest Ninja said:

What do You all think about this?

Mr. Ninja (given name?):

I think the tamahagane coming from smelters is graded (5 I think) so it can be mixed in various amounts by the smith. Note in the pic below there are two grades coming from the Yasukuni smelter being sent to various arsenals. This adds to the variability. In addition, the smith has a lot of control over how the metal is heated, folded, pounded, etc. So I don't personally think blades are in danger of being too generic. I think about the example of two RJT smiths with vastly different values both using the same tamahagane from Yasukuni.

Just my two cents (Oh wait, the US doesn't make pennies any more.)

 

John C.

[klee]

This a great topic

 

As Lewis stated above,

 

Tamahagane production/distribution became more and more centralized as time went on. This was also a gradual process throughout the koto periods but really became mainstream in shinto ( edo ) periods.

 

While it could be argued that steel quality became more consistant , it inevitably lost all the regional characteristics of steel that once appeared in the old works.

 

There is ( and will always be ) much great debates trying to pin down the cause for the great artistic ( not functional ) decline in swords over time and the loss of regional characteristics of steel likely has a big part in it

[ROKUJURO]

Forest NINJA (please sign all posts with at least a first name plus an initial. It is a rule here so we can address each other in a polite manner. You can add your name to your profile), 

I have explained this several times here on NMB, but again:

TAMAHAGANE is a very basic form of metallic iron. It can have differnt amounts of impurities (= NOT ALLOY METALS !). The low temperature of its production process (around 1250 - 1300°C) is not high enough to reduce other alloying element oxides that may be present in the iron ore (there are always other elements like manganese, chromium, silica, copper, titanium, a.s.o.).

You cannot "mix in" other metals into the process unless you throw modern alloyed steel in the TATARA. Another method would be the OROSHIGANE process where iron can be carbonized but also modern alloyed steel could be introduced. Traditionally, this is of course not done. Steel alloys can only be made in hot liquified state - roughly 1.600°C or more.

The TATARA process does not produce melted (= cast) iron, at least not in considerable amounts but more as an unwanted by-product. Nevertheless, even these small amounts of cast iron are sold and used by some swordsmiths to increase the carbon content of their steel.

The TATARA method (comparable to the early European bloomery furnace) produces a very pure iron as far as alloy metals are concerned, but it is not "clean" in hindsight to impurities like silica and metals that are attached to it like titanium. So even in the 'best' TAMAHAGANE, you will find very small amounts of impurities. 

The traditional swordsmith does not care for them; he is solely interested in the carbon content. Carbon is introduced into the iron by the charcoal used in the process, but is is not automatically distributed homogeneously. There are spots with higher heat in the TATARA furnace where the iron takes on more carbon than in "cooler" places. This is why repeated forging (= stretching out, folding and fire-welding) is required later for refining. 

From a metallurgical view of the subject, differences in the appearance of sword-steel and its properties are mainly due to the work of the swordsmith. How he treated the metal in the long process has probably much more influence than tiny amounts of a few impurities. However, it is known that some elements like titanium can have an effect even in very small amounts in an alloy.

Since there are no actual comparative scientific tests on authentic Japanese sword blades, we will probably not know much about this subject. However, ASANO TARO, a swordsmith in GIFU, has executed final fracture tests on a blade (on YouTube under asanokajiya).   

[Brian]

Jean, some interesting research has been done...
Note, if any of these break copyright, let me know and I'll delete them

Kuji Iron Sands.pdf Characteristic_Feature_Found_in_Typical_TATARA-Product-Japanese-Sword.pdf Control_of_slag_and_inclusions_in_traditional_Japanese_iron_and-steelmaking.pdf

[ROKUJURO]

Thank you Brian,

stuff to read through for a while!

I hope the 1925 research on KUJI SATETSU is no longer secret now! 

[Laters]

6 hours ago, ROKUJURO said:

Forest NINJA (please sign all posts with at least a first name plus an initial. It is a rule here so we can address each other in a polite manner. You can add your name to your profile), 

I have explained this several times here on NMB, but again:
 

 

Why is it that every Forum has a person being a fkhead?

 

Signed FOREST NINJA 

[ROKUJURO]

Don't feel bad for it.

[Brian]

We REQUIRE at least a first name. No-one wants to address you as either Mr Ninja, or just Forest.
If you wish to ignore that rule, then my advice is run Forest, run.
 

[eternal_newbie]

Unless your first name actually happens to be Forest/Forrest, in which case please update your name field to reflect that

[Laters]

3 hours ago, Brian said:

We REQUIRE at least a first name. No-one wants to address you as either Mr Ninja, or just Forest.
If you wish to ignore that rule, then my advice is run Forest, run.
 

Delete My account.

 

I came here to learn about Katana's, etc.

 

Not for some idiot(s) to worry about My personal details like a Stalker.

 

So yeah, delete My account

Edited March 30 by Laters

[Lewis B]

PS You don't need to give your 'actual' name.

[Scogg]

It’s a rule we all follow to learn about katanas on this platform.

 

I think Reddit is anonymous, if that’s what you’re after 

[ROKUJURO]

Sam,

I know and understood well. But if someone (Laters) comes to this wonderful forum to learn, the terminology is the first thing to adapt to. This may appear strange and difficullt to some newcomers, but it is the way we all had to go if we wanted to dive into that theme.

The funny thing is that even most native Japanese have to learn the terms and the correct reading of names.

[Brian]

2 hours ago, Lewis B said:

PS You don't need to give your 'actual' name.

Yes you do. 
And if I find out people are giving fake first names, I'll suspend them or take action. There is nothing wrong with a forum requiring at least a first name. Either in your username, or your signature, or signing your posts. We don't even require a surname or even an initial. So if that's too much for people to bear, then this isn't the place for them. Even a nickname based on your first name is tolerated, such as Hamish with his "Hamfish" That is at least making an effort. But some anonymous name and refusing to give a name we can call you by? Sorry...then this is the wrong sandpit for you.
No, we don't delete accounts. This isn't an airport, no need to announce your departure. Just don't log in.
 

[Robert S]

I for one am extremely glad that this group insists on real names.  Keeps the discussion real.

 

Back to the topic, I found the discussion in the Kitamura et.al paper (Control of Slag and Inclusions...) that Brian linked extremely interesting.  I had always assumed, due to the temperatures involved, that tamahagane accumulated by a sintering process.  However, that paper indicates that that was probably only true prior to the 17th century.  From the 17th century onwards, the paper posits that much or most of the tamahagane was created by crystalization from molten pig iron.  This would imply that there ,may have been a meaningful change in the nature of the steel, broadly associated with the Shinto period.  It also raises the question of inclusions versus alloying that Jean raised earlier.

[ROKUJURO]

Robert,

analyses of TAMAHAGANE show that it is very pure, regarding alloy metals, but I have no data of KOTO and SHINTO era steel for comparison.
What I think is important is that there is a very narrow temperature margin in the bloomery/TATARA process. Unlike many other metals, iron has a slightly wider temperature span between 'solid' and 'liquid'. This feature is making the direct reduction process possible. But you cannot leave this temperature area by much without metallurgical changes taking place.

Usually, the intent is to have a good degree of efficiency in the process which rises with the temperature. Celtic and early medieval bloomery furnaces were around 30% (= 30 kg iron from 100 kg of iron ore) and were run at about 1.250 to 1.300°C. The temperature in a TATARA can be even a bit higher which means that near the vents, the iron wil be closer to melting temperature. The problem is that with rising temperature, the iron 'absorbs' more carbon. The malleability of iron ends with a carbon content of 2,02%; this is the limit where cast iron/pig iron starts to be formed.   

Crystallization can only take place from a liquid state, so if TAMAHAGANE was made at very high temperatures (= above 1.350°C), there is a high risk that it would not be workable on the anvil. Cast iron (roughly 2 - 5% C) will shatter like a cookie under the hammer. As far as I know, historical Japanese iron technology is not known for decarburizing processes (with the exception of OROSHIGANE, but this worked in another way) as we had them in the Middle Ages in Europe. So, the Japanese were forced to stay with the TATARA method.

We should not forget that in medieval Japan, ALL iron was produced solely in TATARA, and most of the products coming out of the forge were made from (low carbon) iron, not steel! This was the same in Europe, by the way.

Coming back to a potential technological leap after the KOTO era, a slightly higher carbon content in the steel might indeed make a difference in working it and in the properties, but we can exclude 'secret' alloy metals mixed in the TAMAHAGANE - or missing in EDO times.

There are still more factors which can influence steel properties and the performance data of steel blades, but that would lead a bit far.  

BUT we should consider the fact that - starting with EDO JIDAI - many swordsmiths no longer made their own steel, and as you know, there is a big difference between potatoes that you grow in your own garden, and those you can buy in the supermarket!  


 

[ROKUJURO]

Just by accident, I found this on YouTube:
 

I get the impression the author is using old data sheets, which may mean that newer research was not done. Basically he is telling nothing new or surprizing.