Casting vs Carving

[laowho]

Well, thank you Ian. If there's anything to these possibilities/considerations, I hardly know where else to look but here at the NMB. I can understand if, in the absence of evidence to the contrary, members here would naturally default to an insistence not only upon the quality of Japanese craftsmanship generally, but especially with regard to all things nihonto in particular. That said, and with everything you've offered, it certainly doesn't help me since experience and familiarity seem to be the best (only?) real guarantors of "hand made" authenticity. I'll stick with vendors I can trust for now. Thanks.

[Guido]

This topic has been discussed ad nauseam on this board - Ford allone has written pages about it. There's a huge difference between alloy or iron casting, and steel casting. First trials of steel casting were done in 1841 by Jacob Mayer, and patented on Dec. 16, 1851. And it took many more years until this production method reached Japan.

 

But I have a solution: let's vote on it. Those who think that the Japanese had invented it earlier and were able to keep it a secrect, please raise your hands!

[Soshin]

This topic has been discussed ad nauseam on this board - Ford allone has written pages about it.

 

Hi Guido,

 

Very true.

 

Hi Doug C.,

 

Come on use the nice search function on the message board. This topic has been discussed to death.

[Steve Waszak]

My understanding of decarburation is that it would result in reduced ductility, reduced strength, and the formation of cracks, making it more vulnerable to breaking. And this is to be sought? What am I missing/misunderstanding here?

 

Steve

[cabowen]

Depends on the atmosphere in which the decarb occurs...Cracking and loss of ductility are issues when it happens in a hydrogen environment and is called hydrogen attack.

 

The real issue with this theory is that normal decarb is mostly a surface effect. It would be extremely difficult-some might say near impossible given the tech available-to decarb through the body of a tsuba plate.

[Steve Waszak]

Just following up on Ian's previous post on decarburation, would the Japanese of the period he is referencing have been able to control the local environment for hydrogen presence/concentrations? My understanding is that hydrogen-induced problems might be mitigated via the use of steel with very low levels of impurities, by heating the material to remove absorbed hydrogen, and/or by modifying/controlling the local environment to reduce hydrogen charging. Would any or all of these methods have been known/available to the craftsmen in question in the period(s) under discussion?

 

It seems to me, too, that what you say, Chris, about only the surface metal being affecting (and leaving the internal material virtually or wholly unfazed) would indeed be the case, even if decarburation were beneficial (I'm still having difficulty understanding how the usually negative effects on steel's ductility and strength via decarburation would be eliminated [in fact reversed] via some process used by the craftsman in the years we're referencing, unless, I suppose, the answer to my question in the paragraph above is yes.

 

Cheers,

 

Steve

[ROKUJURO]

My understanding of decarburization is that it would result in reduced ductility, reduced strength, and the formation of cracks, making it more vulnerable to breaking. And this is to be sought? What am I missing/misunderstanding here?

 

Steve

You are missing what Ian refers to: Decarburization is done with cast iron which has a very high carbon content (up to 4 -5 %). If the process is controlled, the result will be malleable cast iron which has a number of useful applications.

 

Decarburization of a tool steel (having roughly about 0.5 to 1.3 % carbon) will indeed result in a lower quality with loss of strength and possible hardness.

 

The whole discussion is useless without practical experience and profound knowledge of metallurgy. Exchange of opinions will not lead to better knowledge.

[Guido]

If the process is controlled, the result will be malleable cast iron ...

...

The whole discussion is useless without practical experience and profound knowledge of metallurgy.

Since you entered the discussion, I hope you will do just that: share your knowledge. For instance, what is this "controlled process"?

[laowho]

Hi Guido, David,

 

Of course I should have done this first (used the search function), but I did try it immediately afterward and have since been lost in a maze of decarburized surface layering. I've also tried to beg off politely, especially after Ian's post. Dunno what else to say. I answered Kevin because he asked for clarification, and felt that Ian's post required/deserved recognition. That's all I've done since asking the question. But it does tickle me that you've rejoined the fray, Guido. Must be to properly place your cease and desist request. I've been out of it from the beginning, but am happy to read anything I can on the matter. And you never know...some particularly adroit thread may get linked here.

[IanB]

In my previous post I said nothing about casting steel nor did I suggest that cast iron tsuba were left as such. I also made the point that there was no reason whatsoever why a tsuba should not be forged from bloomery iron and then shaped with chisels and scrapers into its final form. What I tried to point out is that the Chinese were definitely making malleable objects by removing carbon from cast iron and that if such a process were applied to the making of sukashi tsuba it would reduce the labour involved enormously. In ' Iron and Steel in Ancient China' Donald B. Wagner describes the decarburising process used in China in which the carbon content of the cast iron object is lowered by heating in an oxidising atmosphere. He also points out that hydrogen and steam would not be a factor in the pre-modern technique. He describes how the cast object was packed in closed pots with iron oxide (often haematite or iron scale) having a large percentage of Fe2O3. He also states that it is important to mix this with previously used packing material (which is largely Fe3O4) in the ration of 1: 3-5 to ensure the required reaction takes place at a rate that allows the carbon time to migrate from deeper layers within the object. From the degree of decarburisation of various Chinese artifacts that have been sectioned and analysed he concludes that the process, when carried out above 1000 C, converts a layer of 2 mm to ferrite and pearlite in about 1.2 days. Because the plate has two sides, some 4mm of the plate are converted to a tough but malleable steel by heating for just over a day. In addition the edges of the apertures will also be subject to the reaction and will loose carbon by exactly the same amount as the upper and lower surfaces. This is hardly a thin surface layer.

I have absolutely no evidence that this was done in Japan and that tsuba were made in this way, but it makes a lot of sense that they were. What is incontrovertible is that the Chinese were doing it many centuries ago and that Japanese iron workers were fully aware of the process since they used it, and still do, for making traditional kettles.

Ian Bottomley

[Steve Waszak]

Thanks for that, Ian. This more detailed explanation helps a lot (at least for me). Do we know what the relative malleability, ductility, and strength of metal produced via this decarburation method would be vs. forged material? From your explanation, I can see where the cast iron would achieve a level of malleability, etc... that would greatly affect its suitability for certain applications. What I wonder, though, is if this level would make products made from it equal to (or perhaps even better than) those made from forging (tsuba, let's say...). I find this discussion fascinating (even if my lack of hands-on metallurgy means I know little of what I'm talking about), so I appreciate the contributions of those who can add their knowledge gained from practical experience.

 

Not sure how related this is, but I find the history/speculation on the history of the Ulfberht viking sword very intriguing as well. Here is a video concerning this topic. No idea if what it presents is loaded with problematic data, sources, etc... http://www.youtube.com/watch?v=nXbLyVpWsVM

 

Cheers,

 

Steve

[christianmalterre]

here´s an excellent read by one professional metallurgue!

i equally do hard recomment(!) to browse the various references given in charts and in the addenda herein!

unfortunately only in German-for those who can read this language;very certainly an big enrichment!

 

http://www.schwertbruecken.de/pdf/staehle.pdf

 

Christian

[ROKUJURO]

.....I hope you will do just that: share your knowledge. For instance, what is this "controlled process"?

Guido,

 

Ian was faster than me and gave a basic description. Not too much is known about how exactly the Chinese proceeded, but today we know what is necessary to decarburize cast iron to produce the desired material. It is not necessary to copy the text here, it can be read under

 

http://en.wikipedia.org/wiki/Malleable_iron.

[cabowen]

Should be rather simple to take an old, thought to be cast tsuba, section it, and check for spherical carbides to confirm it was converted to malleable cast iron.

[IanB]

?

 

On a Japanese auction site.

Ian Bottomley

[kusunokimasahige]

A coaster ?

 

[kaigunair]

How about a cast tea pot with a built in tsuba theme? For casting work, the nanako looks quite detailed to my untrained eyes. Slight possibility this is in fact soldered onto the pot, but I can't tell with the photo angles provided. And this is probably a modern piece meiji or post work and not Edo period, so this might lessen its applicability to this thread ....

 

Still, is an example of the possibilities of detailed cast work + possibly post casting work ( this is not a top grade example by any means)...

 

http://page15.auctions.yahoo.co.jp/jp/a ... t398226007