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Zach Gordon




Location: Vermont. USA
Joined: 07 Oct 2008

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PostPosted: Thu 30 Jul, 2009 4:58 pm    Post subject: Piled Structure         Reply with quote

Hi I have heard allot about piled stucture in the roman era and I was wondering how it was different from pattern welding?
Thnx
Z
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Jared Smith




Location: Tennessee
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PostPosted: Thu 30 Jul, 2009 5:28 pm    Post subject:         Reply with quote

It is only a personal theory, but, I suspect piling was most likely done to reduce brittleness in period pieces of bloomery iron. Many "piled" sections artifacts have very low levels of martensite/bainite (phases of metal grain structure that hardens and tempers well.) This suggests to me that they actually reduced carbon content during the piling process.

I have yet to form a sincere opinion on the historical purpose of pattern welding. It seems probable that it was a way of combining iron from different sources, and saving the known best "tool edge" materials for that edge region in the finished piece. The cosmetic beauty of it was commented on by early 5th century, and I suspect cosmetics were a real motivation for pattern welding then as it is now in our modern extremes of it.

Absence of evidence is not necessarily evidence of absence!
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Zach Gordon




Location: Vermont. USA
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PostPosted: Thu 30 Jul, 2009 11:23 pm    Post subject:         Reply with quote

Right, I think I'm pretty sure what pattern welding is. But what is "piled structure" is it just merl folded over a bunch of times or something else?
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Jeroen Zuiderwijk
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Location: Netherlands
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PostPosted: Fri 31 Jul, 2009 12:37 am    Post subject:         Reply with quote

Zach Gordon wrote:
Right, I think I'm pretty sure what pattern welding is. But what is "piled structure" is it just merl folded over a bunch of times or something else?
Any bloomery iron or steel has a piled structure. You get that when forging out the slag and other impurities. This is done by forging the metal into rods, and folding it and forging it down again and repeating that until enough slag is removed. More piling can be done when carburizing iron into steel. As carbon only enters the outer layers, the iron/steel gets folded to distribute the carbon evenly throughout the steel. Even more piling can be done in patternwelding, where alternating layers of steel and iron can be welded together, to get a linear pattern. These can either be used to forge the entire blade (such as in late Celtic swords), or as billets to be combined into more complex patternwelded swords.
Jeroen Zuiderwijk
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Kirk Lee Spencer




Location: Texas
Joined: 24 Oct 2003

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PostPosted: Fri 31 Jul, 2009 11:45 am    Post subject: Re: Piled Structure         Reply with quote

Zach Gordon wrote:
Hi I have heard allot about piled stucture in the roman era and I was wondering how it was different from pattern welding?
Thnx
Z


Hi Zach...

Best I understand, "Piled" structure is when wires of iron and steely iron are piled and welded together. Can be seen in celtic swords. This thread may be of interest in this context:

http://www.myArmoury.com/talk/viewtopic.php?t=1485

Eventually wires became bars (billets) which were welded together side by side. I have heard that in celtic swords these bars were twisted (torsion), though I have never seen any pictures of these swords. I have seen a drawing of a celtic or celto-roman sword in an Osprey book that showed the tang twisted to make it thicker and stronger. I have often thought it might be this technique which inspired the idea of twisting the billets to make them thicker and help distribute and squeeze out slag deposits. IMHO is is when the billets are twisted that the term "pattern-welding" is used because as the fuller is cut through the whirls on the twisted bars it creates various patterns, from herring-bone like structures near the surface to star like patterns deeper in, to "blood-eddy" like circular patterns near the center. Also sections of the billets could be left straight while sections in between left straight, then these alternate sections can be arranged in various patterns side by side before welded together making a larger more complex line or checkerboard pattern across the blade core. Here is a link to illustrate this.

http://www.templ.net/english/making-blades.php

By first century A.D. there are Roman pugio blades with torsion pattern welding. But by late Roman times, as the bog finds, especially Illerup Adal, shows tremendous experimentation with pattern-welding, including what appears to be mosaic "damascus" like billets.



 Attachment: 149.16 KB
PiledStructureInPompeiiGlad.jpg
Pompeii Gladius with Piled Structure

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Pugio.BladesPW.BN.RLW.jpg
Pugio blade with torsion pattern welding from first century A.D.

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SPATH.IllerupRivetRepair..jpg
Illerup Gladius with torsion pattern welding.

Two swords
Lit in Edenís flame
One of iron and one of ink
To place within a bloody hand
One of God or one of man
Our souls to one of
Two eternities
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Jared Smith




Location: Tennessee
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PostPosted: Fri 31 Jul, 2009 1:49 pm    Post subject:         Reply with quote

Great post Kirk! I have been looking for Roman era examples of it.
I had read that Romans saw the Germanic tribes make blades with techniques that I would interpret as early pattern welding / forge combining different materials. This does not seem to be written down until around 200 A.D. But, I know that evidence of this in blade cross section from finds in North Italy Celtic villages goes back to around 5th or 6th century B.C.

Absence of evidence is not necessarily evidence of absence!
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