Friday, May 28, 2010

Layered vs Pattern Weld / Forge vs Foundry

This is another commentary arising from a discussion on Norsefolk about weapons making technology of the Viking Age - wandering well off that historic mark!

I wanted to ask you about your use of terminology with regard to pattern welded and damascus steel. You said that modern bladesmiths use the term 'pattern welding' incorrectly to refer to all layered or patterned steels. Why do you say this is incorrect? Also, my understanding of the term 'damascus steel' is that it only refers properly to the wootz steel sold in medieval Damascus, Syria, which developed a pattern not from layering but from striation in the crucible. Am I mistaken?

The history of modern work with layered steels is confusing of itself!
This is how I make the shape of it:

There was a body of existing objects in museums, primarily weapons:
• Swords (mainly) from roughly 200 - 1100 AD in Northern Europe with low layers, twisted rods
• Blades from roughly 1200 - 1500 in the Middle East with medium to high layers, cut to create geometric designs
• Blades from Persia and India (have not looked as close here, so dates??) with mottled appearance (actually a crucible process)
• Blades from roughly 1300 - 1600 in Japan with extreme layering to the point layers disappear

The problem was that outside of Japan (and maybe something in India) the actual methods used to produce these objects was pretty much totally lost as working techniques into our modern times

In the 1960's, two independent efforts were made to relearn the methods:
• One team working out of the British Museum, focused specifically on North European swords (most specifically Sutton Hoo). Any illustrations you see around suggesting the use of braided round rods comes from these early attempts (those methods do not really work all that well, by the way)
• In the USA, Bill Moran pioneered variations on the Middle Eastern 'flat stack to geometric' methods.

So the initial problem on language is that two entirely different groups, the Museum / Art Historians and the Bladesmiths, working quite independently, developed similar (but different) terms. Often the same language had different meanings (and just close enough together to really confuse the issue).

I personally tend to lean to the museum set.

The first point : 'Pattern Welding' vs 'Layered Steel' :
Any method where a alternate layers of metal is welded into a block is Layered Steel. This could include completely modern methods, like fused powder and sheet. Pattern welding most specifically refers to Northern European method of twisting low count rods, then welding those rods to a block. So it is correct to say that all Pattern Welding is Layered Steel, but NOT all Layered Steel is in fact Pattern Welded!
Elaborated in an earlier blog posts :
Re-inventing Layered Steels
More on Pattern Welding - What and Why
Layered Steels 3 On Materials
(plus who knows how many other pieces, try a search here under 'layered steel')

One nice case in point 'Damascus' and ' Damascene' :
• 'Damascus' steel here refers to a method of creating quite even, flat stacks, with medium to high count (200 - 500 layers). These flat stacks are then cut or punched, then flattened, to create regular, geometric patterns. (Many modern bladesmiths call this method 'pattern welding' - even though that specific term is a museum definition for the N. European method of twisting rods.)
• 'Damascene' really should apply to the foundry / crucible methods. Often however. Damascene is used interchangeable (and incorrectly) with Damascus - and also to refer to steel blades with inlaid precious metals (to really confuse everything).

Now, just to mess everything up even more (!) - there are two main ways to use foundry / crucible methods:
• One is to seal some mid to high carbon metal in a crucible, bring it up to molten temperatures, then slowly let it cool. As the metal cools, the carbon selectively migrates to the first cold areas (the outside of the mass). What you get is a shape like this : O : where the dark lines are the highest carbon, the blank centre is low carbon. If you compress that into a blade you get : V : where there is a packing of the high carbon into the cutting edge.
• The second is to take a pile of lower carbon plates, and wire them tightly and place them into a bath of molten very high carbon. Capillary action then draws a thin film of the high carbon up between the plates. Now grind for effect.
Other terms that get inserted into *this* confusion are : 'Watered Steel' / 'Persian Steel' / 'Wootz'

I am the first to warn you that I have not studied the possible foundry methods in any detail. I'm pretty sure those few that do work in these techniques (also just recently 're-invented) would be just as picky about use of language.

I would refer you to an excellent article on line by 'H. Foll' :
Damascene Technique in Metal Working

I'm not sure that any of this may clear up the terminology confusion!


No comments:


February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE