Not online. I have read accounts of battle, and using Katanas against armor is just plain a bad idea. Moreover, just look at their actual battle-gear. Samurai carried swords, but only as a tertiary weapon.
Well, it looks like i may have been wrong about that one. However, I note that much of legendary skill attributed to Japanese swordsmiths was pure hokum.
Cite? No, again, not online. But you can go around some ancient European battlefields and still find more or less intact swords lying around (buried, because only those were not taken by human scavengers). Their not usable, but intact. Most mid-to-later Japanese swords simply fall apart too quickly.
Heh. the best of them were extremely good indeed. Thing is, the best examples of anything tend to be very good indeed, the more relevant question being how good was the average katana? Maybe they were rather prone to breaking - I have no data. If you have an offline cite, I’d be sufficiently interested to get myself to the library.
This is an interesting one. I once spent the best part of a year carrying out metallurgcical research on Anglo-Saxon and Roman blades from around 500-1000 AD. The samples were mostly knives, and they were mostly made of dense rust - it required x-rays to locate the metal areas and cut them out for investigation. Of course, these were very old blades.
At the time I was trawling through the scientific and archaological literature on the subject, including that on katanas. All the articles I read concerned very well made blades - using charcoal hearths, plain steels and blacksmithing techniques they were about as good as you can get. But I fully concede that there may have been a bias towards research on excellent blades - “A Metallurgical Appraisal of a Shoddy Katana” isn’t that snappy a paper title.
Much more recently I carried out a bit of materials consultancy for a hydro-power generator in Scotland, who were looking at refurbishing fifty-year old plant. Surprisingly, a lot of unprotected steel components were in near-perfect condition despite continuous exposure to acidic peat waters. I did a little research and found that peat bogs appear to have a preserving effect on iron and steel articles, against all logic. Indeed, they were regarded as good locations for finding iron meteorites. They may contain some kind of natural corrosion inhibitor - there are a few. The point being, the environment is an important factor when considering the corrosion resistance of an item - you can’t simply look at examples from Japan and Europe and conclude that the Japanese steel corroded excessively fast. Not saying it didn’t, just not convinced of it yet.
I don’t believe Japanese steel corroded any faster than European steel, though the properties were a bit different.
The common myth is that the Katana is the sharpest, most surable sword that ever existed. People who buy into the myth tend to point to the Japanese swordsmiths who used techniques (such as folding the steel) unheard of in Europe.
Of course this is nonsense. Europeans were pattern welding their blades since the migration era. It wasn’t until the middle ages that pattern welding fell by the wayside, but only because higher quality mono steels were available. In contrast, Japanese steel was simply not of the quality needed to make good sword blades, hence, they continued to use folding in order to homogenize the impurities. This process actually removes some fo the carbon form the steel, so the myth of the 1000 folds swords of incredible strength, are exactly, that, myths.
In practice I found the following to be true (having handled quality European replicas, as well as some quality Katanas):
European swords could be just as sharp as any Katana.
European swords are MUCH more springy.
Katanas are much more likely to take a set (bend and stay bent) due to their design.
European blades are lighter per inch of length than Katana, this is also due to their design (European blades tend to use distal tapering a lot, something most historically accurate Katana use very little or not at all).
The Katana is a sword of beauty, but so is a patternwelded viking sword, or a later medieval longsword. There is no such thing as the ‘perfect’ sword. There is only a good tool for a particular job.
Always value your input on a sword thread, Kinthalis!
Not too surprising. Some of the knives I looked at had high-carbon inserts for the cutting edge that had been quenched to over 800 HV. Impressive.
These two facts are not unrelated!
It is a counter-intuitive fact that all plain and low alloy steels are more-or-less equally springy, regardless of their hardness. I.e. spring wire and paperclip wire are equally springy, or equally stiff if you prefer. The reason we don’t percieve them to be so is that the paperclip wire yields (takes a permanent “set”) at a much lower deflection than the spring wire. But if you were to measure the force vs. deflection for both wires, they are the same provided you stay below the yield deflection of the paperclip wire.
The relative springyness of the European blades is probably entirely related to their different cross sections and taper, and unrelated to the steel.
That’s news to me. Is it a result of the cross-section shape?
The myth has probably arisen from a confusion between the number of folding operations and the number of layers that result. Each folding doubles the layers, so ten folds gives 1024 layers and twenty folds gives over 1000,000.
Folding achieves a number of things. The first thing to realise is that the steel was never molten during its generation - the charcoal furnaces only get to about 1200 Celcius, which isn’t hot enough. Instead the iron oxide ore is reduced by hot carbon monoxide via the gas-solid interface.
Initially the ore consists of haematite and magnetite, mixed in with a fair bit of crap, mainly sand (silica). The furnace reduces the ore to FeO, which fluxes the sand to form a low melting temperature glass called fayalite. Most of this runs to the bottom of the furnace, but a proportion is retained within the metal. Eventually the remaining FeO is is reduced to a spongy mass of steel particles, loosely sintered together, full of pores and blobs of molten fayalite, with the carbon content all over the place.
Folding closes the pores and turns the metal into a solid mass. It also squeezes out most of the liquid fayalite, which forms a spray of bright droplets during the hammering operation. The remaining fayalite inclusions are flattened and aligned along the sword axis, where they have little effect on its properties. Finally, folding homogenises the carbon content in the ingot being folded. By initially separating the steel from the bottom, middle and top of the furnace, you get ingots of fairly homogenous high, medium and low carbon steel for the various parts of the katana.
Producing steel in larger furnaces, using coke as a fuel and increasing the forced draught gets the temperature high enough to melt the steel, which runs to the bottom with all the slag and crap floating on top. By tapping from the bottom you get a cleaner, homogenous steel, no folding required. I’m not too sure how the carbon content was controlled though - I only know about ancient and modern smelting, with everything in between a bit vague.
I think they rolled worked iron in straw as they folded it to increase the carbon content. Least thats what my teacher always told me…he’d seen sword blades being made in Japan (according to him at least). The amount of straw used, and when the iron blocks were rolled in it was carefully controlled and passed down from teacher to student (again according to my teacher).
I do find myself posting in just about every one for some reason
Interesting, and what you say certainly melds in quite well with what I’ve heard. However, it has been pointed out to me that the heat treatment the metal receives also affects this property, what do you think?
It is a function of the blade geometry as I understand it, yes, combined with the differential tempering used by the Jepanese creating a softer back and a harder edge.
I appreciate the details you mentioned here, most of which I did not know
The variation due to heat treatment should in theory be small. This tangentially related paper (which I heartily recommend you don’t read) measured a Youngs Modulus range of 209-212 GPa for a low alloy steel subjected to various heat treatments. That’s not a great deal of variation.
A second effect that may make a difference is that the structure of quenched steel is less dense than slow-cooled steel - quenching makes the sword get bigger! Take two initially identical swords, heat both bright cherry red and air-cool one and water quench the other, and the water-quenched one will be a few percent larger. Tempering the quenched sword will make it contract by an amount increasing with the degree of the temper. So different heat treatments actually result in different sized cross-sections, although again this effect is quite small.
This raises a third possibility - the effect of the residual stresses induced by differential quenching and carbon content variation. High carbon cutting edges and lower carbon cores means the cutting edges end up in compression - their attempted volume increase during the quench is partly constrained by the core. That might affect the springiness of the blade as a whole.
That makes some sense - the straw would instantly burn, perhaps dusting the surfaces in fine soot. That would then diffuse into the metal as it was-reheated between folding operations. Again this is news to me, but I would expect a fair degree of variation between smiths, and also the jealous guarding of trade secrets!
