page_title: Laminated steel blade
section_title: Other uses of laminated steel
hierarchical_section_title: Laminated steel blade / Other uses of laminated steel
caption_attribution_description: English: Katana - Showing alternating layers of hardenability. In this photo, lighter colored layers have a higher carbon content than the darker layers. In reality, which layer is lighter or darker depends on the angle it is viewed from compared to the lighting. Visible on the right hand side of the photo is the nioi, which can be seen as a bright thin line about a millimeter or two wide surrounding the hardened edge of the yakiba. The nioi is made up of niye, which are single martinsite crystals surrounded by pearlite. The streaks of niye that whisp away from the hardened edge result from the forged in layeres of different steel.[1] References ↑ "A History of Metallography" by Cyril Smith
context_page_description: A laminated steel blade or piled steel is a knife, sword, or other tool blade made out of layers of differing types of steel, rather than a single homogeneous alloy. The earliest steel blades were laminated out of necessity, due to the early bloomery method of smelting iron, which made production of steel expensive and inconsistent. Laminated steel offered both a way to average out the properties of the steel, as well as a way to restrict high carbon steel to the areas that needed it most. Laminated steel blades are still produced today for specialized applications, where different requirements at different points in the blade are met by use of different alloys, forged together into a single blade.
context_section_description: Since producing high carbon steel from wrought iron was very difficult, careful lamination of different alloys also served to conserve this difficult-to-make steel by using it only for the parts of the blades where it was needed. Many swords were made with the minimum possible amount of high carbon steel along the cutting edge, with the rest of the blade being made of low carbon steel or wrought iron. A thin strip of high carbon steel could be laminated between two layers of softer steel, or a core of soft steel could be wrapped in high carbon steel. The Japanese katana was often found with complex patterns of soft and hard steels; having 5 sections of differing hardness welded together to form the final blade was not uncommon. The end result would be a blade with a very high carbon edge (as much as 1.0%, equal to the highest carbon content found in low alloy steels in use today) and a softer spine. The very hard, but brittle, edge made the swords extremely sharp, while the spine gave the blade flexibility, so that it would bend rather than break.
  Many laminated steel blades, particularly those of the Vikings, also used complex structures of steel to produce  patterns in the surface of the steel. These patterns were made by manipulating the piles, by twisting or otherwise distorting the piles, before they were forged into the blade.
caption: A Japanese katana. The outer skin is forged from alternating layers of steel with differing carbon content, and folded upon itself many times, producing a mokume (wood-eye) pattern.
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