Elements of Steel
IRON - Primary element of steel
CARBON - The most important element for hardening, and for strength
MANGANESE - Grain structure of the steel, hardening and wear resistance
MOLYBDENUM - Prevents brittleness and maintains the steel’s strength at high temperatures
COBALT - For hardness and corrosion resistance
CHROMIUM - Important for corrosion resistance. Steel having 11.5% to 13% chromium is considered stainless
VANADIUM - Essential for giving the blade its ability to harden. Also for wear resistance and toughness of the blade, as well as the ability to take a very sharp edge.
Types of Japanese Steel
While edge design, blade shape and handle construction are important features of the knives in the Korin collection, the distinctive element of each knife is the steel used to make it. Japanese knife makers have always chosen their materials carefully, and today’s chef knives are forged with similar methods that were used by traditional sword craftsmen for generations. The knives in Korin’s collection are forged out of many different types of steel- from hard high carbon shiro-ko steel to stain resistant steel. We encourage you to browse through our collection to find the type of knife most suited to your needs.
Carbon steel knives are made of iron combined with 0.1-2.7% Carbon. Carbon is the key ingredient as iron cannot be tempered, or hardened without it. Although carbon increases steel’s hardness, it reduces rust resistance, and makes steel more fragile than stain resistant knives. Steel is made up of iron, carbon, and small percentages of other elements such as silicon, manganese, phosphorus and sulfur.
Stain Resistant Steel
Adding at least 12% chromium-oxide to the basic mixture of iron and carbon produces the stain resistant steel commonly used by Japanese knife brands. A chromium-oxide film forms on the metal’s surface that prevents the iron from coming into contact with oxygen and water. However, stain resistant knives must still be washed after each use as salt and acidic ingredients can erode the chromium-oxide film and reduce the knife’s rust resistant.
As Technology advances, new types of steel are being developed that increase the performance of carbon steel with practical benefits of stain-resistant steel. High-carbon, stain resistant steels such as Ginsan-ko, Inox, VG-10, and 8A are becoming increasingly popular with professionals and are used in the production of both traditional and western style knives.
Cobalt is a naturally occurring inclusive mineral found in various ores used in the preparation of magnetic, wear-resistant, and high strength alloys. Knife manufacturers who are forging knives from metals such as VG-10 and Ginsan-ko have an added benefit due to the cobalt content already present in these two types of steel.
Shiro-ko & Ao-ko Carbon Steels
Shiro-ko steel is highly refined carbon steel that does not have additional compounds, though it may contain varying levels of impurities, phosphorus, and sulfur. Adding chromium and tungsten to shiro-ko steel creates ao-ko steel, which makes the knife more durable and capable of maintaining a longer edge retention than a shiro-ko blade.
Tamahagane is a rare and precious metal that is used to forge the katana. Tamahagane steel is only produced two to four times a year due to the tremendous amount of the labor, material and wasted material that is required to make a very small amount of it. 13 tons of iron sand and 13 tons of coal must be smelted, then hammered for three days and three nights to produce a mere 2.8 tons of raw steel (kera). Once the kera is produced, less than 1 ton of the kera is considered tamahagane steel. The 1 ton of tamagane steel is controlled by the Society for Preservation of Japanese Art Swords, which is sponsored and established by the Japanese Government. The tamahagane steel is sold exclusively to katana craftsmen a few times a year. However, even within the 1 ton of tamahagane steel only 200 kg is considered usable high quality A1 steel, and katana craftsmen are limited to 10 kg of this A1 steel.