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Rajavidya Das Hargreaves




Location: Washington State, USA
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PostPosted: Sat 13 Sep, 2008 10:14 am    Post subject: Folded Steel         Reply with quote

Hi,

What are the functional advantages of folded steel?

I did a search for folded steel and didn't come up with much but If this question has been asked before, I apologize and humbly ask someone to point me to the existing thread.

Thanks very much!

Raj-
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Justin King
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PostPosted: Sat 13 Sep, 2008 11:24 am    Post subject:         Reply with quote

The historical methods of producing steel often produced material with high content of slag and other inclusions and typically the carbon content would be uneven in distribution throughout a single billet. Folding (laminating) and drawing out a billet helped to even out the distribution of these elements and drew the inclusions into lenthwise "strands" within the billet, producing a more consistent piece of steel.
The steel making processes used in modern times produce very homogenous steel that would benefit little from folding.
The thread "Japanese Steel" touches on a bit of this in more detail, and the subject has been discussed in other threads as well.
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Rajavidya Das Hargreaves




Location: Washington State, USA
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PostPosted: Sat 13 Sep, 2008 3:30 pm    Post subject:         Reply with quote

Thanks for the reply Justin.

So if modern methods produce better steel then why do some modern sword makers offer to fold the blade thousands of times? What does that do for the sword?

For example, this forge will fold blades like that: http://www.zheng-wu.com.

Thanks,

Raj-
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Chad Arnow
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PostPosted: Sat 13 Sep, 2008 4:04 pm    Post subject:         Reply with quote

Rajavidya Das Hargreaves wrote:


So if modern methods produce better steel then why do some modern sword makers offer to fold the blade thousands of times? What does that do for the sword?



Pattern-welding and forge-folding are still done because 1) some people like the way it looks, 2) some people think it's more historical on certain swords, and 3) some people still believe it's superior to modern monosteels. Happy

To answer your question, "What does that do for the sword?": simply put, raise its pricetag considerably. Happy

Happy

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Joel Minturn





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PostPosted: Sat 13 Sep, 2008 5:23 pm    Post subject:         Reply with quote

As I understand it folding steel has one other benefit as well. The layers created by folding steel help to stop the propagation of cracks. Basically any cracks that form will only open lengthen to the boundary of the layer of the steel. Kind of like how side walk cracks only stay on that piece of side walk. I could see where the folded steel would be a huge advantage with less homogeneous steels but with with modern steels not sure if that would be a real advantage or not.
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Chad Arnow
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PostPosted: Sat 13 Sep, 2008 5:42 pm    Post subject:         Reply with quote

Joel Minturn wrote:
As I understand it folding steel has one other benefit as well. The layers created by folding steel help to stop the propagation of cracks. Basically any cracks that form will only open lengthen to the boundary of the layer of the steel. Kind of like how side walk cracks only stay on that piece of side walk. I could see where the folded steel would be a huge advantage with less homogeneous steels but with with modern steels not sure if that would be a real advantage or not.


Perhaps true, but there's also a likelihood the blade could be weaker overall because of the number of welds. Every weld is a potential weak spot if not done properly. Not enough flux, some slag, whatever. You need to trust the person doing the folding and not just buy folded steel because it's folded. Happy

Happy

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Michael Olsen





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PostPosted: Sun 14 Sep, 2008 8:07 am    Post subject:         Reply with quote

Rajavidya Das Hargreaves wrote:

So if modern methods produce better steel then why do some modern sword makers offer to fold the blade thousands of times? What does that do for the sword?


Hi Rajavidya,

Unless I am mistaken (in which case, someone please correct me!), a sword with a "thousand layers" is not folded a thousand times. You see, every time the steel is folded, the prior number of layers is doubled.

1. Start with one layer, fold it to make two.
2. Fold that for four.
3. Fold that for eight.
4. Fold that for sixteen...
5. that for 32,
6. again for 64,
7. one more for 128,
8. again for 256,
9. again for 512,
10. again for 1024

Also, as was pointed out, each fold produces an opportunity for the blade to become weaker or stronger - if the smith isn't very capable a folded blade could turn out very poorly.

Another interesting element is in the impact of diminishing marginal benefit - in other words, after a certain point more folding of the blade produces virtually no impact in the quality of the steel. It's like mixing salt in water - after a certain point the salt just won't get "more dissolved".

I hope that helps,

Michael

Michael Olsen
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Rajavidya Das Hargreaves




Location: Washington State, USA
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PostPosted: Sun 14 Sep, 2008 8:18 am    Post subject:         Reply with quote

Thanks very much everyone.

Lot's of great information... I learned alot! Happy

Well, that does it then... no folded steel for me...

Thanks again! myArmoury.com rocks!

Raj-
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Gabriel Lebec
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PostPosted: Sun 14 Sep, 2008 3:57 pm    Post subject:         Reply with quote

Rajavidya Das Hargreaves wrote:
Well, that does it then... no folded steel for me...

I don't quite think that was the message... Razz I'd hate to think you'd swear off ever getting any nihonto! Wink

"The most beautiful experience we can have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science." - Albert Einstein
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D. Austin
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PostPosted: Sun 14 Sep, 2008 5:45 pm    Post subject:         Reply with quote

One other theory to add to the list. When I was 14, I saw a man folding steel to make knives and he explained to me that as the layers were of alternating hard and soft steel, the edge would stay sharp longer. The idea being that with use, the softer layers are worn away quicker, leaving a sharp hard layer exposed. When this layer breaks off, the process is repeated, leaving the next hard layer exposed. I believed him at the time but now I'm not so sure it works that way.

I do have a folded steel tanto in my collection. Why did I choose it? Because I think it looks cool and I like the romantic kind of notions that a blade of 1000 layers conjures up. I don't really mind whether or not the folding adds any functional advantages.
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Michael Olsen





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PostPosted: Sun 14 Sep, 2008 6:41 pm    Post subject:         Reply with quote

Rajavidya Das Hargreaves wrote:
Thanks very much everyone.

Lot's of great information... I learned alot! Happy

Well, that does it then... no folded steel for me...

Thanks again! myArmoury.com rocks!


Hi Rajavidya,

As Gabriel said up there ^, the message isn't "don't buy folded steel". It's great stuff when made by a competent smith. And that's the catch.

It doesn't mean it has to be an antique nihonto. It doesn't mean it has to be prohibitively expensive (at least, I don't think it does...)

It just means, as always, make sure that whatever you are buying (be it swords and armour, or beer and pancakes) comes from a good reputable source. The internet makes it easy to get recommendations and first-hand opinions of products (check the "Reviews" section of this site if you want an example).

Best,

Michael

Michael Olsen
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Rajavidya Das Hargreaves




Location: Washington State, USA
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PostPosted: Sun 14 Sep, 2008 10:00 pm    Post subject:         Reply with quote

Michael,

Point taken...

Though at the moment I am seeing less of an advantage and more of a price tag with folded steel(just with the pieces that I'm considering).

And again, thanks for all the great information guys!

Raj-
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G Ezell
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PostPosted: Mon 15 Sep, 2008 7:52 am    Post subject:         Reply with quote

D. Austin wrote:
One other theory to add to the list. When I was 14, I saw a man folding steel to make knives and he explained to me that as the layers were of alternating hard and soft steel, the edge would stay sharp longer. The idea being that with use, the softer layers are worn away quicker, leaving a sharp hard layer exposed. When this layer breaks off, the process is repeated, leaving the next hard layer exposed. I believed him at the time but now I'm not so sure it works that way.

I do have a folded steel tanto in my collection. Why did I choose it? Because I think it looks cool and I like the romantic kind of notions that a blade of 1000 layers conjures up. I don't really mind whether or not the folding adds any functional advantages.

I don't agree with this smith either, carbon migrates across the layers as the steel is welded, after a few folds there will be no significant differences in the hardness from one layer to the next, unless due to something besides carbon. Mixing a high carbon steel with a low carbon steel will, in effect, result in a medium carbon steel, unless the folding is kept to an absolute minimum (as in the case of a san-mai type construction).
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Steven H




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PostPosted: Mon 15 Sep, 2008 9:37 am    Post subject:         Reply with quote

G Ezell wrote:
D. Austin wrote:
One other theory to add to the list. When I was 14, I saw a man folding steel to make knives and he explained to me that as the layers were of alternating hard and soft steel, the edge would stay sharp longer. The idea being that with use, the softer layers are worn away quicker, leaving a sharp hard layer exposed. When this layer breaks off, the process is repeated, leaving the next hard layer exposed. I believed him at the time but now I'm not so sure it works that way.

I do have a folded steel tanto in my collection. Why did I choose it? Because I think it looks cool and I like the romantic kind of notions that a blade of 1000 layers conjures up. I don't really mind whether or not the folding adds any functional advantages.

I don't agree with this smith either, carbon migrates across the layers as the steel is welded, after a few folds there will be no significant differences in the hardness from one layer to the next, unless due to something besides carbon. Mixing a high carbon steel with a low carbon steel will, in effect, result in a medium carbon steel, unless the folding is kept to an absolute minimum (as in the case of a san-mai type construction).


Mr. Ezell-

And this, historically, is why it was done. Early smiths didn't know about carbon content per se. But they could tell hard iron from soft and mixed them for better swords.

Cheers,
Steven

Kunstbruder - Boston area Historical Combat Study
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Dan Howard




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PostPosted: Mon 15 Sep, 2008 3:50 pm    Post subject:         Reply with quote

Wootz works in a similar way as described above. It develops a good cutting edge due to microserrations caused by softer iron wearing more qiuckly than the harder carbides.
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Rajavidya Das Hargreaves




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PostPosted: Wed 17 Sep, 2008 7:39 am    Post subject:         Reply with quote

Anyone have any experience with San-Mai? Is there any difference between it and folded steel?

Thanks,

Raj-
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Gabriel Lebec
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PostPosted: Wed 17 Sep, 2008 8:12 am    Post subject:         Reply with quote

Rajavidya Das Hargreaves wrote:
Anyone have any experience with San-Mai? Is there any difference between it and folded steel?

Sanmai is a lamination technique commonly used in Japanese swords. It is a separate concept from folded steel; the individual steel pieces can be folded (common for jacket steel) or monosteel (sometimes with the core steel, especially in modern Japanese-style swords). But when they are then welded together into the blade blank that's it - no more folding occurs.

Lamination techniques increase the difficulty of forging, the labor-related expense, and the probability that something will go wrong. It is, after all, a blade-length weld of two or more pieces of steel. The functional benefits could include using steels for the core/edge vs the jacket/spine that work better with the differential hardening heat treatment than any one steel would, as well as saving the clearest and prettiest work for the jacket steel.

I have heard enthusiastic claims about the potential metallurgical benefits of much more complex lamination methods or how the physical forces in a cut are redistributed through the laminates resulting in a superblade, etc. I remain skeptical of such assertions. One should consider that soft iron cores could in some cases be used simply for economic (supply of good steel) rather than functional reasons.

I can see an argument for some of the simpler schemes, though, and the resulting complexity adds one more impressive feature (sometimes including subtle visual distinctions) to an already impressive object.

"The most beautiful experience we can have is the mysterious. It is the fundamental emotion that stands at the cradle of true art and true science." - Albert Einstein
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Last edited by Gabriel Lebec on Wed 17 Sep, 2008 8:18 am; edited 1 time in total
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