Steel Analysis Of Different Regional Schools

[Valric]

I'm currently trying to wrap my head on the differences in steel composition from Koto period swords. 

 

Has there been any metallurgic analysis done to compare steel from different regions? 

 

What I'm basically trying to get at is how much can we say that the technics of a particular, geographically-located lineage of smiths was an adaption to the characteristics of the local iron sand deposits compared to technical aspects that are not material dependant. 

 

We often hear that "steel quality" is the main reason early work cannot be reproduced by Gendai smiths. However, if we had detailed composition data we could in theory reproduce the steel composition and we could see the magnificent koto-style hada and activities that made these swords famous. This is corroborated by the observations of Yasutsugu who could produce superior hamons through re-tempering of old koto blades compared to his own. At least we could take the steel variable out of the equation. 

 

If this is the case then I'm not sure the current centralised "traditional" bloomery steel production in Japan is best way to keep the tradition alive if you're striving for reproducing excellence. If hard data on skin and core steel composition was available we could reproduce the composition of these steels. 

 

Besides, it is well possible that the smiths of old time had a secret formulae for their bloomery steel. Now I'm not a metallurgist but say, in crucible steel production (which happens at a much, much higher temperature) you can infuse elements. (say, vanadium). 

 

Overall my intuition is that technic has been overestimated in the production of these masterworks if technic is understood as an adaptation to raw materials. If we had a time machine and brought Masamune along and gave him the NBTHK Tamahagane he will produce a Soshu-style gendai blade not a Masamune. 

[Carlo Giuseppe Tacchini]

Chris, do you really think that noone had your same idea until now ?

Me think broken or dead blades were and are available for destructive analisys but if results are not published anywhere either they are inconclusive or too different from each other to obtain a reply to your question.

[ROKUJURO]

Chris,

if you read a little about archaeometallurgy, you will find that the bloomery process (all bloomery processes world-wide!) yields a very pure iron. Besides carbon and silicon, there are only very small quantities of trace elements and they do not influence the properties of the steel a lot. The quality of the iron or steel is much more influenced by the forging process itself, the number of foldings, the conditions and the decarburizing effects the steel is exposed to in the fire.

In the bloomery process, alloying elements cannot be added to the steel. For this you would need, as you wrote correctly, high temperatures above the melting point of iron (1.578°C), as you can have in blast furnace. But then you get cast iron with a carbon content of about 4% which is not malleable. In the modern TATARA process, you get the whole range from low carbon steel to high carbon steel to small amounts of cast iron. Not all of this can be used immediately for sword making, but nothing is lost. Non suitable qualities can be reprocessed in an OROSHIGANE furnace (refining furnace).  

So I think that the main differences between KOTO and SHINTO blades are to be found in way the steel was worked with. 

But that is only my personal view.

[Jussi Ekholm]

There was one quite recent article few years ago at Tōken Bijutsu 664 title of it translated by Markus is "Comparison of jigane from different domestic satetsu sources".

[Carlo Giuseppe Tacchini]

Thanks Jussi. Maybe it's around in the board or the net. I'll make a try to find it.

[christianmalterre]

Chris

 

there are some metallurgical analysis done and equally published.....

i will have a look....

(just for the beginning into this, i do hard recomment you so to read the articles published in JSSUS about "steel" and refinement of iron ores - written by Mr. (? forgot his name) Prof. Cauthino)

 

just Google for this....those were online available, least some time ago...

 

if not longer online ?- do PM me and i´ll throw you the essayes via PM as i did safe me this material on pdf (somewhere)....

 

Christian

[Jussi Ekholm]

Unfortunately Carlo I think the article has never been online and only the original Japanese language version as in the magazine. I have the issue and I looked at it briefly and tried looking at it but translating at my Japanese level is not possible. (I must have at least dozen NBTHK articles pinned that I should run through Markus at some point )

 

I quote myself from another thread:

 

 

NBTHK Token Bijutsu 664 - Article by Naruki Issei (I hope I got his name correctly) - Comparison of satetsu from various parts of country and the results in homemade steel (that is about the loose translation). 10 examples were made and the result explained and studied. My Japanese is not good enough to read it and give an explanation of it. But I believe it explains how different starting material results in some features being different. For examples some test examples were darker in color, some produced chikei, kinsuji could easily be seen on some etc.

 

Very interesting stuff but unfortunately too advanced for me.

 

Some other interesting NBTHK articles (which I unfortunately cannot read, just browse) include these (and there are lots of more interesting articles over the years in the magazine)

 

Experimenting with satetsu from Kamakura Bay

Investigations on steel from Sakauchi (坂内) in Mino province

 

Christian mentioned that Mr. Coutinho has published extremely useful articles to JSSUS over the years. I am not sure if this is article that Christian meant but here is 3 part article series from 2008. (I will post links to it but if it is problem to Mr. Coutinho or JSSUS they can of course be removed)

 

One problem three solutions: The steel of the European, Indo-Persian and Japanese swords compared by F.A.B. Coutinho

 

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-1-European_swords.Artigo_sobre_ac.pdf

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-2-Indo-Persian-swords-final.pdf

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-3-Japanese-swords.pdf

[SAS]

Perhaps it is a language issue, but I suggest that in fact there are trace elements in the iron sands used for tamahagane, and in fact these trace elements end up incorporated in the end product, regardless of whether or not they have been placed into solution through reaching a melting point (they have not.) This has been well establish by a number of metallurgical studies published. I think we are revisiting this subject, and it has been covered here before.

[Okiiimo]

I've learned from this board that what I once thought were unique questions and perspectives weren't very unique, they were just new to me.

[Valric]

Thank you for all the replies. 

 

Carlo, 

 

I'm hoping someone had a look, that's why I ask! It seems to me that running chemical analysis on the raw materials used by geographically-distinct schools is such a basic low-hanging fruit I can't believe it hasn't been done. 

 

Jean,

 

the idea that bloomery process yields "pure steel" only varying in carbon content has been challenged to say the least. Bloomery steel is in fact full of impurities, the only notable difference is that the temperatures are insufficient to melt (most) of the trace elements into the iron, as steve points out. These "macro-level" impurities are beaten out but they persist. Japanese swords are full of impurities, in fact. And some smiths used these impurities to create more durable steel in the folding process. 

 

e.g.  https://www.esomat.org/articles/esomat/pdf/2009/01/esomat2009_02024.pdf 

 

Density of "impurities" vary naturally from the raw material and the smith's work. Now the word impurity is perhaps not ideal in this context, because we that these impurities influence the properties of the steel. For instance while high phosphorous steel is ill-suited to make swords, traces of vanadium found in indian wootz have been shown to improve the structural properties of the steel. Modern metallurgic, especially the field of high-grade crucible steels for specialized applications relies these adjunct elements to form extremely tough steels. Now one could argue that we're confusing inclusions versus homogeneous distribution (and carbide formation) but I think it's quite clear that they both have an effect. 

 

Jussi, 

 

Having a translation of the Naruki article would be great, it looks very promising.

 

I'm not impressed however by the "one problem three solutions Part 2" as it's really doesn't do a good job at presenting wootz. But it's understandable given that the major headway in understanding the stuff has only been done in the past few years. However the first part on on late medieval era swords was interesting - I've read also that Europeans in the late medieval era failed at forging imported wootz cake because they overheated it, leading to all sorts of superstitions about the indo-persian smiths. The vikings managed just fine, however. But I'm drifting so far off-topic...  

[Ruben]

Hi Gentlemen,

 

a question that puzzled me for long time is, what happens to the damaged sword and polearms collected from the battlefields?

In times of great battles, I´am sure many swords, spears and other arms were "recycled".

I´am pretty shure starting the sword making process with such material makes a difference.

In peaceful times maybe it was more necessary to use steel from tatra process and from broken tea pots, like to day.

I can imagine that some of the hada seen in koto period swords are a result of using other swords in the making.

 

Greetings

 

ruben

[Darcy]

 

 

a question that puzzled me for long time is, what happens to the damaged sword and polearms collected from the battlefields?

 

221 o-suriage mumei koto wakizashi that are Juyo Token say "people picked em up and fixed em up as good as they could if the blade was worth saving"

 

I'd expect that purified iron is a resources as anything else is and if the sword was beyond redemption it was something that a swordsmith could still break down, mix in with new material, and end up with raw material in making a new sword.

 

I'm really enjoying the articles above, thanks Jussi for putting them up.

[ROKUJURO]

Chris,

we should not mix up trace elements, impurities, and alloying elements. Not everything in the steels has physical or technical effects.

I just got a sample of an analysis of a (probably modern) steel, and I was asked about the possible properties:

Iron       = 97,07 %

Manganese = 1,318 %

Nickel   = 0,183 %

Molybdenum = 0,30 %

 

Vanadium = 0,095 %

Platinium = 0,091 %

Chromium= 0,082%

Mercury   = 0,072%

Gallium    = 0,053 %

Arsenic     = 0,072 %

Germanium= 0,020 %

Copper      = 0,010 %

Palladium  =0,020 %

Silver        = 0,020 %

Cadmium   = 0,051 %

Indium      =  0,030 %

Tin            = 0,051%

Antimony  = 0,051 %

Zinc          = 0,010 %

Tungsten  = 0,025 %

Niobium   = 0,020 %

Titanium  =  0,030 %

Gold        =  0,020 %

Cobalt     =  0,020%

Lead        =  0,020 %

Zirconium = 0,051 %

Iridium     = 0,0010 %

Bismuth    = 0,0010 %

Rhenium   = 0,0010 %

Hafnium    = 0,0010 %

Rhodium   = 0,0020 %

Yttrium      = 0,0051 %

Bromine    = 0,0051 %

Ruthenium= 0,0051%

Tantalum   = 0,00012 %

We see that the extensive use of scrap steel added to the blast furnace content leads to a strange mixture. These steels cannot be refined/freed from accompanying elements without a lot of work and costs.  

Bloomery steel - and TATARA steel is basically the same - cannot contain much more than carbon as alloying element. Silicon is brought into the steel from the slag, and the amount of this can be controlled/reduced by refining the steel in the forge. There were scientific researches done on that matter. The SATETSU has generally low amounts of phosphorus and sulphur, and the charcoal used in the TATARA is almost free of these detrimental elements.

There are discussions about the effect of Titanium which is brought into the steel via contamination with slag, but there is no evidence and I doubt it will because of the low content.

Elements found in Tamahagane 

C: 1.00% to 1.42%
P: 0.013% - 0.042%
S: 0.006% -0.008%
Mn: 0.006% - 0.11%
V: 0.004% - 0.015%
Al: 0.003% - 0.02%
Ti: 0.003% - 0.0267%
Cr: 0.69% - 1.54%
Mo: 0.04%
Si: 0.018% - 0.02%

I will add again, that alloyed steels cannot be quenched in water without the immanent risk of failure, while pure carbon steel has to be quenched this way to obtain the desired hardness. 

Indian or modern 'Crystallisation or crucible damascus' (also called wootz/bulat) are a completely other cup of SENCHA. Besides others, Vanadium is necessary in this steel to induce crystallisation, while the same element can form very hard carbides (with big particle size) in modern stainless cutting steels. 

The problem is that the discussion about steel metallurgy is not necessarily related to Japanese sword steel alone. It applies to the physics of iron in general, and any mystification could lead the wrong way.     

 

Jean,

 

the idea that bloomery process yields "pure steel" only varying in carbon content has been challenged to say the least. Bloomery steel is in fact full of impurities, the only notable difference is that the temperatures are insufficient to melt (most) of the trace elements into the iron, as steve points out. These "macro-level" impurities are beaten out but they persist. Japanese swords are full of impurities, in fact. And some smiths used these impurities to create more durable steel in the folding process. 

 

e.g.  https://www.esomat.org/articles/esomat/pdf/2009/01/esomat2009_02024.pdf 

 

Density of "impurities" vary naturally from the raw material and the smith's work. Now the word impurity is perhaps not ideal in this context, because we (believe?) that these impurities influence the properties of the steel. For instance while high phosphorous steel is ill-suited to make swords, traces of vanadium found in indian wootz have been shown to improve the structural properties of the steel. Modern metallurgic, especially the field of high-grade crucible steels for specialized applications relies these adjunct elements to form extremely tough steels. Now one could argue that we're confusing inclusions versus homogeneous distribution (and carbide formation) but I think it's quite clear that they both have an effect..... 

 

 

[Carlo Giuseppe Tacchini]

 

Christian mentioned that Mr. Coutinho has published extremely useful articles to JSSUS over the years. I am not sure if this is article that Christian meant but here is 3 part article series from 2008. (I will post links to it but if it is problem to Mr. Coutinho or JSSUS they can of course be removed)

 

One problem three solutions: The steel of the European, Indo-Persian and Japanese swords compared by F.A.B. Coutinho

 

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-1-European_swords.Artigo_sobre_ac.pdf

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-2-Indo-Persian-swords-final.pdf

http://www.naippe.fm.usp.br/arquivos/hobby/Artigo-3-Japanese-swords.pdf

Yes, I remember now that you mention them. Me and Mr Coutinho exchanged mails about the Japanese part and about wootz. He wrote many other useful articles for the JSSUS just around the time I wrote mine. 

 

Guess if he still remember me and if it's around here on the board.

[Valric]

Thank you Jean for your in-depth answer. It's enlightening. 

 

But then what is your point of view on this, that the regional iron ore deposits (and their composition) has no discernible effects on the craft? Or do I read you wrong. It seems to me that the regional characteristics of iron ore deposits are often invoked as the reason why it's easier to kantei koto-period smiths compared to say, shinshinto, when iron production was centralized. 

 

As for old swords being recycled, that's an interesting point. Reforging the blade would lead to a lot of carbon loss and hence, I suppose you could use it to make core iron. I read tea kettles and old temple nails were used by some shinto smiths to make blades in the old style (I think Kotetsu did this, hence the name meaning "old iron"). Also, do you think that namban tetsu was indian wootz cakes? or something else? I suppose it would make sense given the likely maritime trajectory of the traders in that time. But do we have any hard evidence of this or is it just a conjecture based on the visual account that it looked like "iron cakes".

[flemming]

To address the original question; hitachi metals details the 5 kinds of iron sand regionally found in Japan. See section on iron sand...

 

http://www.hitachi-metals.co.jp/e/tatara/index.htm

 

Lloyd Flemming

[Valric]

Blown away, thank you. That was a fascinating read Lloyd, the most detailed information on iron manufacturing in Japan I've seen.  

[ROKUJURO]

Chris,

as I wrote, the chemical composition of iron ore will always differ from one mining location to another, but the iron production process and the high temperature chemistry involved will always remain the same, the physical nature of iron does not change. Trace elements contained in the bloomery may vary a lot, but as long as they remain very small percentages, they will not influence the properties of the steel in a significant way.

Of course some elements can have different effects depending on their content. Carbon makes a lot of a difference in the range between, say, 0,3 and 1,5%, but we have to respect that this element is easily introduced into the iron in the TATARA process. Other alloying metals like Vanadium, Tungsten, Chromium, and Cobalt can also change the properties of steel considerably when added in small quantities, but this works only in a blast furnace which melts the iron to a liquid state so the atoms can move freely.

The hunt for 'old iron' continues to this day and not only in Japan! I am constantly on the search, and if I find a piece of iron which I can date to pre-industrial production, I can be very sure that it is almost free from non-desired alloy elements.

Water kettles are cast iron (high carbon content) and can as easily be recycled in an OROSHIGANE furnace as old blades, nails, and tools. The smith can always test the resulting steel for its properties (= carbon content) and so combine the parts of a new blade.

I have no information about raw wootz being traded into Japan, but it would not make sense to me. Wootz has to be treated in a completely different way compared to the Japanese way of the craft. There are many dozens of cycles of heating and hammering the steel necessary  to bring out the cristalline structure, and for a Japanese swordsmith, a wootz cake would just be some foreign (very expensive) steel.

In addition to that, the very special composition of wootz steel with its 'exotic' alloy elements like Vanadium would certainly have shown up in the steel analyses of Japanese blades.  

I believe that the introduction of NANBAN TETSU has to do with a certain curiosity of the Japanese metal workers. They may have regarded the West and its technical achievements as superior to their own iron producing techniques and hoped probably for better results. But iron remains chemically iron, so no miracles in swordsmithing happened.      

[Carlo Giuseppe Tacchini]

Blown away, thank you. That was a fascinating read Lloyd, the most detailed information on iron manufacturing in Japan I've seen.  

 

Chris, as per the diffusion of the different types of furnace see pages 24 to 27 of my essay (link below) and follow the bibliography for more info.