Massdrop IV inspired: what is "wrought" cladding? How is it different from iron or carbon?

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rmrf

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I thought about posting this stupid question in the massdrop page, but I figured this was a more appropriate forum.

What is wrought (iron?) cladding and how is it different from the iron clad or carbon (steel?) clad knives that seem to be common from japanese smiths?

I did a quick search and I saw someone said wrought iron cladding is easier to abrade than soft stainless or anything mono. It also seems like a lot of european or us based makers work with wrought iron. What are the benefits and what makes this special? Is it an aesthetic thing like a softer damascus cladding? Is it less reactive than iron or carbon cladding? To be fair, I'm also not sure what the difference between iron and carbon cladded knives are...
 

MSicardCutlery

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It's mostly just an aesthetic difference. Wrought iron is very low carbon, and somewhat impure by modern standards. It hasn't been made in decades commercially. It seems there are many ways to produce it, but speaking generally, it's just drawn out bloomery iron. It has a pattern all its own from sealed slag inclusions, and layers if it has been cut and restacked. Practically speaking the traditional method of making tamahagne into swords (drawing and folding) is the process of refining a bloom into wrought steel. I've undertaken this process, and up to a certain point....it's an absolute b**** to forge. All it wants to do it crack, but because of the slag content, it welds very easily, so failures are quickly corrected. Modern low carbon "mild" steel can be had with carbon content in the range of wrought iron, but it's homogenous. Wrought iron is also supposed to weather better than mild steel in outdoor applications because of the slag content too, if memory serves.
 
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It's mostly just an aesthetic difference. Wrought iron is very low carbon, and somewhat impure by modern standards. It hasn't been made in decades commercially. It seems there are many ways to produce it, but speaking generally, it's just drawn out bloomery iron. It has a pattern all its own from sealed slag inclusions, and layers if it has been cut and restacked. Practically speaking the traditional method of making tamahagne into swords (drawing and folding) is the process of refining a bloom into wrought steel. I've undertaken this process, and up to a certain point....it's an absolute b**** to forge. All it wants to do it crack, but because of the slag content, it welds very easily, so failures are quickly corrected. Modern low carbon "mild" steel can be had with carbon content in the range of wrought iron, but it's homogenous. Wrought iron is also supposed to weather better than mild steel in outdoor applications because of the slag content too, if memory serves.

Interesting. So the slag actually helps heal cracks? I don't have a steel background but in the world I play in, slag/dross is evil so that's fascinating to me. Thanks for weighing in.
 

MSicardCutlery

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Interesting. So the slag actually helps heal cracks? I don't have a steel background but in the world I play in, slag/dross is evil so that's fascinating to me. Thanks for weighing in.
The slag is usually molten sand of some kind, silica, so it acts like a sort of mild flux preventing oxidization to the degree that you see with modern steels. In effect the steel is self fluxing, up to a point, according to Walter Sorrels, about 4-5 folds IIRC. By then the inclusions have been stretched and much of the slag has been extruded through the elongation of the inclusions/voids it was contained in. The voids, now being clear of slag are free to weld shut at temperature, creating random little white weld seams (the Japanese have a name for these, it escapes me at the moment) that become part of the surface pattern.

The slag does inhibit the strength of the steel, industrial wrought must be worked "with the grain" or it will fail, even in simple applications like nails. If memory serves, the Titanic's hull failure was also largely attributed to the rivets being either made of inferior quality wrought, or wrought iron period as opposed to steel.

Always happy to ramble.
 

McMan

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There are historical dimensions too:
Wrought iron hasn't been produced commercially in the US since the late-60s and in the UK since the early-70s. The wrought iron used for cladding is usually salvaged (old railings, etc.). IIRC Dan Prendergast made some knives with wrought from the 1700s.
Aesthetically, old wrought can get a nice woodgrain/birch bark look. Polishes beautifully with multiple hues of grey. Looks a bit like linear+organic damascus. Personally, I really like the look. Reactive though.
See below, which is about Japanese chisels, but the same generally holds true for knives:
 
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In my experience, wrought iron is (or at least feels) softer than the standard iron that many blades are clad with. Not only does this make it easier to maintain geometry over time, but it also means that the contrast between the core and cladding can be extreme. Also easier to get a nice detailed polish on finer stones.

This could all be metallurgically rubbish, but it’s how things feel on the stones to me
 

lemeneid

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Wrought can also be made from recycled railway tracks or old metal beams, etc… if I recall
 

captaincaed

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In use I find its less reactive than soft iron. By a lot. It still stinks if you get your nose up to it but leaves the food cleaner. If you cook western vegetables and don't dig patina, it's a win.

Doesn't hurt that it's pretty.
 

Ruso

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Any pictures of actual knives with wrought clad?
 
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Non polished one
 

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northside

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It’s also a really fun knife for the user. There are so many different ways to etch and/or polish it that give very different results in appearance and future patina development.
 
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What is wrought (iron?) cladding

I wrote this in a previous post:

'Wrought' means worked... its roots are Germanic! To this end... I feel like 'wrought' iron can be applied in many situations - for instance, hammered mild steel is in some senses 'wrought'. It is also a style - 'wrought' iron decorations are very popular in victorian-era fencing (often with cast-iron filigree balcony decorations). The old material would have been wrought iron... I am sure the new replicas are mild steel.

Wrought iron was made by decarburising high-carbon content alloys (e.g. cast or pig iron) through oxidation. Indeed, as you say, one of the early mass manufacturing methods was through a puddling furnace (the 'Puddeleisen'). Prior to that, bloomeries produced a range of iron alloys across the carbon spectrum. A blacksmith could choose a part of the bloom that suited their needs... or even combine high and low carbon bits of the bloom. Common to these methods is that the process was not particularly clean. The products were not homogeneous and would contain slag inclusions.

To homogenise the steel and remove the slag, the metal was worked (wrought). Because the steel is 'dirty' by modern standards, you can see impurities from the smelting process. By working the steel, the resulting stock can have a nice grain and a layered, pattern-welded look from the folding/working. The contaminants can be really subtle (my preference)... or outright gaudy (meh)!

I doubt wrought iron is manufactured in commercial quantities. Industry would prefer 'clean' mild steel. That is why blacksmiths might collect old steel from railroads, farm equipment... old bridges or ships. The history behind the material can be a nice touch. Seriously enthusiastic blacksmiths might make their own wrought iron from DIY bloom steel.

The next part is potentially controversial....

how is it different from the iron clad or carbon (steel?) clad knives that seem to be common from japanese smiths?

Keep in mind... wrought iron starts off inherently 'dirty'... so like any thing with a variable production process... results may vary and they will from sample to sample. All things being equal... the main difference for the end knife user is aesthetic. I would wager most other (knife user) differences border on mythology and storytelling. Nothing wrong with a bit of romance and history so long as you know that is what you are buying!

Lets exclude all the considerations a blacksmith has to face when forging.... wrought iron is effectively a 'dirty' mild steel! This just means it is a low carbon content steel. It wont harden and it is soft to work. The slag fibers from working puddle/bloom iron into wrought iron are what gives it its beauty. However, the orientation of the slag fibers also changes the mechanical properties of the steel. You dont need particularly stringent material specifications when selecting a knife cladding material. The cladding is not subjected to challenging loads. So wrought iron will do the job. The conversation might be different if we were talking about bridges (which used to be made from wrought iron)!! As for corrosion? I would put this in the 'it depends' department. It depends on what the impurities are. They could have minor electrolytic properties that help prevent corrosion.... they could just be nucleation sites.... In the wash I would say it rusts - as do other mild steels - it just might rust differently.

The story is different for the blacksmith. 'Cleaning' bloom iron by working it (wought) is hard work. That said, eventually this process was mechanised. I believe wrought iron has to be worked hotter. When brought to temperature (near welding?) it is relatively easy to work. It is also relatively easy to forge weld. The downside is that if you work it 'cold' the material is prone to breaking and splitting. I also believe quenching can be 'exciting'. Since wrought iron is soft, does not harden and has built in fault lines, it can tear during quenching. Similarly, quenches with wrought iron may be more prone to warps. A lot of these issues will depend how the cladding is worked and how 'clean' the wrought iron is...
 
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