wow. 3k + for a KOA ISSHIN MANTETSU on ebay

[cabowen]

  Stephen said:

in the words of Steve Martian

 

 

WEEEELLLLL EXCCCCCUSE ME!!! LOL

 

Only if you are swing'in, czechoslovakian love machine.....

[Stephen]

  Quote

Only if you are swing'in, czechoslovakian love machine.....

 

That be me ,,,one WILD and Crazy GUY!

[Kevin]

  cabowen said:

The hardness of the mantetsu blades was considerably less than shinto and shinshinto blades tested and the same as a koto Muramasa. They claim this made them less brittle.

 

Trouble is, Ohmura's data, as it stands, it pretty meaningless. Those are Rockwell C values. He gives a minimum hardness of Rc 50 and a maximum hardness of Rc 72. Now Rc 50 is not far above mild steel whilst Rc 72 is not far from the maximum that you can get from carbon steel.

 

If I had someone who couldn't harden steel within narrower limits than that, I'd sack them before the week was out (if not sooner), cos that is the difference between not doing heat treatment at all and a dead hard edge. I'd expect someone using a furnace to be 2 Rc points apart (e.g. Rc 56-58) on the finished blade. Even a blacksmith with a forge would do better than the figures given by Ohmura.

 

My guess is that the fully annealed blade started off at Rc 50, and the edge hit Rc 72 after yaki-ire, though there are problems with that interpretation. Rc 72 is on a par with an old-fashioned straight razor. The low carbon core steel would get no harder than Rc 50.

 

Interesting that they were using an electric arc furnace for making the iron and a rotary furnace for heat treatment. Quite advanced for the time.

 

Kevin

[cabowen]

Those hardness figures were high, low, and average across the blade profile I believe...That difference is what would be expected with a differentially hardened blade.....

[Kevin]

  cabowen said:

Those hardness figures were high, low, and average across the blade profile I believe...That difference is what would be expected with a differentially hardened blade.....

 

Well, a high of Rc 72 on the edge and a low of Rc 50 on the back would be fine. It's what I'd expect from a good differentially hardened blade. However, the column is given as 'surface of an edge' in English - and what to make of his second column which, in the English translation, is described as 'reverse side of the edge'?

 

BTW, did a bit of digging. If it is anything like modern steelmaking, the small rotary furnace produced the sponge iron from the ore. The process is used today and it produces very high purity iron with extremely low levels of elements such as phosphorous and sulphur, which in any case appear to have been at extremely low levels in Manchurian ore anyway.

 

Steel was probably produced from the sponge iron by the aforementioned electric arc furnace - again, these two processes are used in conjunction today and give you steel with a very precisely controlled carbon content. All in all, it looks like Mantetsu were several decades ahead of the rest of the world.

 

The next stage looks to have been forging a block of folded high carbon steel, then centre-drilling it to give a pipe. That's fairly standard technology for the time - it is how seamless pipe for bicycle frames used to be made. You wouldn’t want a pipe with a seam! They wouldn't have drilled the block entirely through, otherwise you'd have core steel coming out at the kissaki.

 

Into this pipe you'd then put a forged and folded rod and weld the two together – to judge from the photos, using a power hammer. You'd then have to draw it down to the right dimensions, do some finishing work, and heat treat it by yaki-ire using water.

 

That’s the best I can work it out from basic metallurgy and practical thinking. There are gaps in the accounts where I’d like to have more information, and some of the info is a bit garbled. However, you’d need experienced smiths to teach the workers how to fold and weld steel, and how to draw down.

 

The principal difference between the hada of the Koa Isshin and traditional nihonto would therefore seem to lie in origin and function. In traditionally made swords the hada is a by-product of a process designed to make the steel homogenous. Ditto Swedish steel produced by the puddling and cementation process. However, with the Koa Isshin the steel would appear to have been homogenous when it came out of the arc furnace and was folded for the mechanical benefits of using folded steel i.e. achieving the requirement of reducing the likelihood of low temperature brittle fracture. The 1930s was pretty much the extremely early days of studying this phenomenon, and it wasn’t as understood then as it is now. In fact most of the work was done after WW2, especially by the US Navy, who were rather impressed by Liberty ships literally breaking in two, both at sea and in harbour. The problem was that if you have a homogenous steel and a brittle fracture crack starts, it can run, just as it does in glass – I’ve seen a paper of the period that described a 10 foot long crack in a ship as ‘little’. I suppose that it was when compared to one that broke the ship’s back and led to its complete loss.

 

OTOH, if your material has heterogenous areas, the crack stops before it has really started – a bit like plywood.

 

Kevin

[Kevin]

  cabowen said:

The chemical analysis is as follows:

 

 

carbon manganese silicon phosphorus sulfur

 

kawagane: .57 .05 .17 .018 .003

 

shingane: .23 .15 .21 .020 .008

 

The carbon content of the shingane means that it is the equivalent of mild steel. The manganese figure for the shingane is interesting - it would increase the tensile strength of the steel for a given carbon content, plus increasing hardness and wear resistance. In this case the hardness would only be increased by a small amount, so the principal effect would be on tensile strength. Silicon also improves strength and hardness, though it is less effective than manganese.

 

In short, damn all hardening on heat treatment but very tough. :-) Just what you want from a core steel.

 

The carbon content of the kawagane gives it a good balance between ductility and strength when annealed, and has good wear resistance. It will also harden nicely.

 

Kevin

[drdata]

Thanks for the great info Keven, et all.

 

I learn from this site every day.

 

Regards

[gab72]

First one thank a lot at all for very good and interesting discussion.

@Kevin

From your posts I undestand then hada in Mantetsu sword is comingout

for the process to fold the steel to avoid brittle fracture when under very

low temperature of Manchuria winter.

So despite the purpose is different, the result is true hada and not a simulation of it ?

[Kevin]

@gab72

 

Well, I may get disagreements over this, but I'd regard it as a hada. A hada in a nihonto is a visible grain formed by folding metal. A Koa Isshin has a visible grain formed by folding metal - so what else do you call it? It certainly won't be a simulation though it may differ in appearance from that of a traditional nihonto.

 

The alternative is arguing that it isn't a hada because it isn't a nihonto, despite the pattern being formed by folding and forge-welding steel. That seems too narrow an argument to me. It presupposes that only nihonto have hada and non-nihonto have something else, even though the visible grain in both cases is formed in an identical manner.

 

All in all, it has been a fascinating subject to research. What I'd love to learn would be whether they laminated different high carbon steels in the skin steel, rather than just folding one piece of homogenous steel. However, the information isn't there to explore all the questions I'd like to ask. :?

 

For example, the principal difficulty in doing folding and welding is making sure that any oxide scale is excluded. If it isn't, you get slag inclusions, blisters and open welds, which are seen in some nihonto. The usual modern method is to use borax as a flux (though the more aggressive fluorspar can also be used) and work from one end, so that the liquid flux and oxide gets squirted out by the hammer blows. I've no idea what the ancient smiths used (or if they used anything), or what the Mantetsu company used. :?

 

Kevin

[george trotter]

Not a Mantetsuto man myself, but have owned one and seen a fair number of them...I can only comment on the hada question. I was never able to see hada on the one I owned or had access to. A friend went to the trouble of having one re-polished in a postwar polish (about 20 years ago), and seeing it after the polish I could still not see any hada in the fresh polish.

Having said this however, I was told by a Japanese acquaintance in Japan that he owns one and he classes it as gendaito..I don't know if this is his opinion or it has been to shinsa.

Geo.

[Kevin]

@george

 

I've had several pass through my hands, the last one a few weeks ago. There is a hada there, but it is very fine. Sometimes it needs a good polish to see it. Sometimes you might need a magnifying glass to see the details clearly. All the ones I've seen have been ko-itame.

 

Kevin

[Kevin]

BTW, if it is not too off-topic, visible grain is seen in early (i.e. pattern-welded) European swords:

 

http://www.vikingsword.com/serpent.html

 

Although the constructions can be almost as complex as the Japanese sword, the patterns are, to my eyes, rather clumsier. Mind you, they're achieved by twisting rods and then forge-welding them, rather than multiple folding followed by welding. The more folding you do, the finer the pattern gets. Fold it beyond a certain limit and the pattern pretty much becomes invisible to the naked eye.

 

There's a brief and very basic resume here on various blade patterns from a variety of sword-making traditions:

 

http://www.vikingsword.com/ethsword/patterns.html

 

Kevin

[cabowen]

It seems there were several different iterations of the mantetsu-to, and according to the Japanese source cited above, there is no info as to what the differences, if any were between the early, mid, and late blades. It is possible that some were made with folded and forged kawagane, and perhaps others were not.

 

I am open to the possibility that the kawagane was folded and forged, though I have not seen any evidence that proves this conclusively. The mantetsu blades I have seen did not show beyond a doubt a recognizable hada. The literature I have seen to date is not clear on this point either. The point about folding and forging is the only way to produce a blade that resists cold service fracture, in light of the fact that so many traditionally made blades failed, is also not conclusive in my mind.

 

If anything, I will perhaps pay more attention to the next one I come across, and perhaps further information will be found. Another possibility is to section one, though if these are selling now for $3000, that prospect seems unlikely.....

 

Interesting and enjoyable discussion. Thanks to all....

[Kevin]

@Chris

 

It's not just down to homogenous versus heterogenous structure. I remarked in an earlier post that for a given carbon content, grain size – the size of the crystals in the crystalline structure rather than the hada – was also a factor.

 

The crystalline structure can get coarser through the various forging operations if you’re not careful, especially during heat treating. The coarser it is, the more easily the piece will break, as in brittle fracture. The finer it is, the less susceptible it is to brittle fracture. Not surprisingly, susceptibility to cold temperature brittle fracture increases with grain size. OTOH suppress grain growth and you increase the resistance to cold fracture. Modern techniques of getting an ultrafine structure can increase cold fracture resistance seven times. However, these weren’t available in WW2.

 

Now when you make a hamon, there is generally an increase in grain size, as well as a change in the crystalline structure from pearlite to martensite. If there wasn’t, you wouldn’t see the hamon. Increase it too much and the blade will be more susceptible to cold brittle fracture, despite being folded. OTOH, there are modern alloys that have ingredients to suppress grain growth. They’re useless for making a hamon, not because you can’t differentially harden them, but because the hamon would be invisible to the naked eye. They are however extremely tough and would be resistant to cold brittle fracture. However, that’s another technology that wasn’t available in WW2.

 

Now we don’t have enough info on the traditional swords that broke. We don’t know if the failure was a whopping great chip that resulted in a fatal flaw, or whether the blade broke in half, though we do have accounts from feudal Japanese sources of blades breaking. We don’t even know the smiths involved, so we can’t research the details of the hamons involved. However, I’d bet my bottom dollar that grain size was involved, and that in turn depended upon the type of heat treatment involved.

 

It is interesting to note that the Koa Isshin blades seem to have a very fine structure to the hamon which suggests that the heat treatment used kept grain size as small as possible.

 

Kevin

[Kevin]

Thought I'd have a go at making things clearer.

 

There’s a good discussion on the effect of heat on grain size in this 1918 blacksmithing manual:

 

http://www.lostcrafts.com/Farm/Blacksmithing-14.html

 

Overheating a piece of simple carbon steel by as little as 100F/40C will coarsen the grain, as the following exercise shows.

 

Take an old, large, good quality file and grind grooves across it, halfway through the file about one inch apart. Now heat one end to yellow while leaving the other end cold. This creates a temperature gradient across the file. There will be a definite "shadow" that goes across the bar. This is the area where the steel is transforming into austenite. Just to the hot side of that shadow is the correct critical temperature.

 

Next, note which groove the shadow is at and quench the file in water. Having done that, put the file in a vice at the first, hottest, groove and break it off. A gentle tap with a hammer will be all it takes because the grain will be very coarse and weak. Have a look at the fracture - it will be coarse.

 

Continue down the bar breaking bits off, noting how the grain gets finer and stronger as you move to the colder end. Pay special attention to the groove where the shadow was located and the one just above it. This will illustrate a temperature difference of about 100F/40C. Try to remember how subtle the colour difference was between those grooves. It is very, VERY difficult – though not impossible – to judge the right temperature by eye. With a bit of practice you might easily get to 122F/50C of the right temperature but that's still not good enough; if you’re over by more than 100F/40C the grain will start to coarsen, compared to the optimum. How much it coarsens depends on how much you're over temperature. You can turn good steel into junk by quenching from too high a temperature.

 

Holding the blade at the critical temperature for too long prior to quenching will also promote grain growth. For simple steels the standard rule is five minutes per inch of thickness. You'd want to soak a 3/16" blade at temperature for about a minute. Soak it for too long (e.g. 90 seconds) and the grain size increases again.

 

All in all, it isn’t surprising that some traditionally made swords failed due to cold temperature brittle fracture. What is surprising is that more didn’t – and that is an indication of the expertise of the smiths whose swords survived such conditions. Bear in mind that they were doing this all by eye and without modern instruments - it was a hell of an accomplishment.

 

So back to the Koa Isshin - they'd have kept an eye on temperatures with a pyrometer rather than relying on colour. This would keep grain size to the the optimum, again reducing the chance of cold-induced brittle fracture. Mind you, that on its own wouldn't eliminate the risk.

 

BTW, you have the same problem with ceramics - the difference between a good firing and a duff one can be 100C or less, particularly with some glazes.

 

Kevin

[cabowen]

While I am familiar with the causes and effects of grain size, I appreciate the time you took to explain the issue....

 

From what I have been told and from the limited reports I have seen, I have been led to believe that there were indeed large numbers of broken blades- from koto through the oil quenched Seki blades.

 

It is this large number that makes me wonder....

[Kevin]

Interesting. :-)

 

So did they aim for a smaller grain size than was normal for traditionally made blades? The eye versus the pyrometer?

 

Do you have the names of any smiths whose swords failed?

 

Oil quenched blades would suffer from the problems of contemporary homogenous steels.

 

Sorry if I was teaching my grandmother to suck eggs, but not everyone who collects nihonto knows anything about metallurgy or the finer points of making blades.

 

BTW just started getting a proper forge together again. :-) Got the kit to do small work, such as making my girlfriend a small pointing trowel, but missed having a forge for making blades.

 

Kevin

[Kevin]

I may have found something – I know, I'm like a terrier with a bone, but the subject intersts me.

 

Anyway, the composition of the ore may also be important. To paraphrase Ohmura:

 

“Japanese iron sand contains titanium (approx 4.5-6% on the examples he gives). The Manchurian and Chinese ores don’t contain any titanium and are therefore better for sword steel.”

 

Now this puzzled me – titanium is used to reduce grain growth in steel and make it tougher. However, apparently numerous fine titanium carbides at grain boundaries can exert a detrimental influence on the tensile strength of steels containing more than 0.1% carbon, whilst the coarse globular titanium carbides and fine titanium carbides at grain boundaries reduce impact strength. In short, it increases the chance of brittle fracture in steels with more than 0.1% carbon.

 

Now this is probably not an important factor at ‘normal’ temperatures or for small pieces of steel. In any case the amount of titanium is probably reduced (but not eliminated) during the processing of tamahagane. However temperatures of -40C and a nice long sword blade could be another matter altogether. Ohmura remarks that traditional Japanese swords had, from ancient times, suffered from cold-induced brittle fracture. The ores used by Mantetsu contained no titanium at all, and thus differ markedly from Japanese iron sands. It was in great demand by WW2 traditional smiths. This may be the last bit in the jigsaw puzzle.

 

Mantetsu did low temperature tests, according to Ohmura. The temperature in a room at the Railway Research Institute in Dalian was reduced to -40C and the blade left in the room overnight. The next day the blade was taken out of the room and struck against an iron plate or anvil. The cutting edge did not chip or break.

 

Ohmura remarks that the Kwantung Army, which had jurisdiction over Manchuria, required Mantetsu to make swords that could withstand cold winter temperatures. This was a big feature of a Koa-Issin sword. However he says that the test was only described briefly in one document because of military secrecy. Furthermore, Mantetsu only released limited data about the sword to interested parties. They did not describe either the manufacturing process or the production facility because they considered these to be trade secrets. Mind you, given the involvement of the Kwantung Army and the cold-induced brittle fracture test, these were probably also military secrets. Not surprising, given that this plant was well in advance of contemporary Western steel producers. However, this secrecy rather hobbles our ability to understand what was going on.

 

Oh, on the price – Koa Isshin swords have been fetching $2500-$3000 for a wee while now.

 

Kevin

[John A Stuart]

In the article it mentions Uemura TO 4.42%, Koyakamura TO 5.79% However when we look at the types of ore in Japan,

T-Fe Fe203 FeO Si02 CaO MgO AL203 Ti02 V205 P S

Masa 59.00 64.45 24.72 8.40 2.24 1.54 2.34 1.27 0.258 0.064 0.009

Acome 52.07 52.71 19.55 14.50 3.68 0.94 4.98 5.32 0.369 0.095 0.026

It is the Masa iron ore used for making swords, since Acome had always been considered sub-standard for making swords. John

[Mark Green]

And, of course, sword makers did not have access to these numbers until VERY recently.

They had to go from experience, handed down, or learned.

 

Mark G