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FrankStitt's avatar

What process is used to produce layered steel knives? Shun/Calphalon Katana series?

Asked by FrankStitt (125 points ) July 24th, 2012

Shun, as well as Calphalon’s Katana series, have a certain look about their steel, similar to wood grain. I believe, this is called layered or folded steel. I’ve been having trouble deciphering exactly what produces these knives as well the difference between their production.

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10 Answers

Nullo's avatar

Two of several methods for working steel. Google up some stuff on metallurgy, steelsmithing, and the like. Wikipedia is a good place to start, but they don’t really go into depth.

Folding is to steel what kneading is to dough: you fold it over, hammer it flat, fold it over, hammer it flat, etc. for the sake of improving its strength. Layered steel (or else pattern welding, the more advanced form) is where you get several sheets of steel, heat them up, and then hammer them together. A skilled craftsman can produce a visually appealing pattern.
Both sorts exploit properties of steel that cannot be had via methods like drop-forging or die-casting.

graynett's avatar

Every fold in a coke forge adds carbon to the steel to make high carbon tool steel

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bkcunningham's avatar

Do you mean Damascus steel?

downtide's avatar

The steel with a wood grain effect is called Damascus steel. I found an article here which explains how it’s traditionally made.

bkcunningham's avatar

I watched a man making a knife with Damacus steel. As he heated and beat the steel over and over again; beating, pounding and bending the steel over and over blowing billows to keep the fires raging, he told the story of Jesus on the road to Damacus. I’ll never forget that. I bought my former husband a Damascus steel knife.

downtide's avatar

@bkcunningham It’s not just the folding, they introduce layers of carbon to the steel as well, to make the dark lines. The secret is to add enough to get the effect, but not so much that it makes the steel brittle.

hearkat's avatar

I can’t answer your question, but we bought the Calphalon Katana knives and are very happy with them.

hiphiphopflipflapflop's avatar

There is pattern-welded “Damascus” steel that achieves the visual pattern through incorporation of layers of different steels forged together and twisted. I’ve even seen this advertised with stainless steels for pistol slides (and these struck me as truly silly). Pattern welding was pretty much practiced by every culture that worked iron. The Japanese took this to the ultimate development for functional as opposed to aesthetic purposes by incorporating a high carbon steel edge into a composite blade such that after heat-treating, the cutting edge was untempered martensite under compression.

The “true” Damascus steel or wootz was orginally cast in India and made it’s way to forges in Persia. Wootz is ultra-high carbon steel that develops a distinctive network of very large carbides in a steel matrix. The carbides cause the surface effect which can be manipulated by the work of the swordsmith into such things as the “Muhammad’s ladder and roses” pattern.

Here’s a technical paper on Wootz steel blades and here is a list of papers on ancient Damascus steels and modern ultra-high carbon steel research.

hiphiphopflipflapflop's avatar

Well, for the Japanese swordsmiths, a lot of the layering and folding of the steel intended for the sides of the blade could have been motivated by the desire for the many interesting patterns that can be brought out in the finished blade by polishing. A certain amount of folding and refolding is good from the standpoint of breaking up and dispersing or “working out” impurity phases. The notion that the more times the steel has been folded the better the sword cuts and that this holds to higher and higher numbers is a myth.

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