Damascus/Pattern Welding

[Gyakuto]

I watch so many YouTube videos on making Damascus blades: I find then endlessly relaxing. Despite seeing a pattern-welded billet being formed, I’m questioning whether I know at what I’m looking and I hope someone can confirm or otherwise my, thoughts.

This is what I believe to be going on:

The billet is formed by stacking metals of differing composition (steels with differing carbon percentages and /or nickel content usually). These differing metals undergo a differential colour change when reacted with ferric chloride. The stacked metals are forge welded welding together forming a laminar structure rather like geological strata, on the edge of the billet.

Here’s what I’m not sure about. Is the final pattern on the surface of a blade formed from the ‘strata’ of the edge of the billet? In other words, is the billet, at some point, squashed edge wise and the deforming strata finally makes the wavy surface patterns on the blade?

 

[Dirty Dog]

Forget about the "edge" of the billet. There isn't one, while it's a billet.

The plates are stacked and forge welded. This forms strata across the entire piece, not just at the edge. If there are any spots that do not get forge welded together, the billet will delaminate and you'll be starting over. As you hammer, the billet will get longer and wider, but shorter. Once it's all forged welded, the new billet is folded, twisted, and/or cut and restacked. This is repeated until you get your final billet. The more often it is repeated, the more layers you will have. Less layers makes the pattern stand out more. More layers (up to a point) will make the blade cut better, but the pattern will not be as discernable. If you push the layer count high enough, the pattern will completely vanish. Cutting and restacking is the most common, followed by folding. Twisted patterns are the most difficult, because they require you to hammer on what was the side of the billet, which can easily cause delamination.

Some of the pattern is formed by cutting the billet and changing the orientation of the bits as you restack them. The rest is caused by shaping the blade. As the blade thickness changes, different layers are exposed.

The stacked metals are forge welded welding together forming a laminar structure rather like geological strata, on the edge of the billet.

It is actually possible to make a blade in this manner, but they're not actually Damascus. San Mai blades have a single-metal spine with a pattern welded billet forge welded to them to comprise the edge. But that pattern welded bit will still be forged as above.

 

[Gyakuto]

So the patterns I’m seeing are a combination of stack edges, surfaces ends etc?

None of them are really Damascus but pattern welding. True Damascus is ‘Woots Damascus’ and the pattern is a property of the metal ore itself (that’s from another, fascinating Youtube video!😀)

 

[Dirty Dog]

So the patterns I’m seeing are a combination of stack edges, surfaces ends etc?

That and removing parts of layers when grinding the blade.

None of them are really Damascus but pattern welding. True Damascus is ‘Woots Damascus’ and the pattern is a property of the metal ore itself (that’s from another, fascinating Youtube video!😀)

Pretty much anything anyone claims as "fact" about woots casting should be viewed with skepticism. It's pretty much an unknown.

 

[BrendanF]

'Damascus' is commonly used to describe pattern-welded/forge-welded steels - which are as you describe in your post above.
Steel nerds occasionally comment 'that's not damascus/wootz'. This is correct.
Wootz is no mystery, it's simply a crucible steel, wherein the impurities, silica etc create a visual pattern. It has no real relationship to pattern/forge welded steel, other than the conflation/confusion around the term 'damascus'.

 

[Gyakuto]

'Damascus' is commonly used to describe pattern-welded/forge-welded steels - which are as you describe in your post above.
Steel nerds occasionally comment 'that's not damascus/wootz'. This is correct.
Wootz is no mystery, it's simply a crucible steel, wherein the impurities, silica etc create a visual pattern. It has no real relationship to pattern/forge welded steel, other than the conflation/confusion around the term 'damascus'.

Do you know anything about the grain (jihada) in the steel of Japanese swords? In particular ayasugi had, a wavy pattern in the steel.

 

[Dirty Dog]

Do you know anything about the grain (jihada) in the steel of Japanese swords? In particular ayasugi had, a wavy pattern in the steel.

Remember what I said about the number of layers? This goes back to that. Traditional Japanese swords were folded enough that the pattern is pretty much invisible to the naked eye; the layers are too thin. Traditional swords commonly have several thousand layers, and I understand examples exist with upwards of 60,000. Modern pattern welded blades, in which bringing out the pattern is desirable, usually have in the neighborhood of 200 layers. The visible line was created by differential hardening. The edge was coated with clay prior to hardening, which results in the steel heating and cooling differently in the coated and bare sections.
Ayasugi is most commonly produced by cutting or chiseling across the flat of the billet during the forging process. You would also, of course, have to fold the billet a LOT less.