In essence, a kitchen knife is simply a piece of steel with a handle. A good kitchen knife is made of steel. Good steel must be considered a base, a potential that, thanks to the processes of forging, folding and shaping the blade, can only be exploited by experienced craftsmen.
There are three main categories of steels used in the manufacture of kitchen knives. Each category has its pros and cons, depending on the use of the knife.
High-carbon steels (traditional Japanese steels)
Corrosion-resistant steels (VG10)
Powdered steels (ZDP-189 or R2)
But before diving into different types of steel, let’s first explore the main chemical elements of steel and their effect on the characteristics of the kitchen knife.
STEEL CHEMICAL ELEMENTS AND THEIR EFFECT:
Steel is made up of iron (Fe), carbon (C) and smaller amounts of other elements. Carbon (C) is the key element of steel. Without carbon, steel could not be forged or folded. More carbon means harder steel. Steel can contain between 0.1 and 3% carbon.
Iron (Fe): main element of steel.
Carbon (C): key element in steel. This gives the steel the ability to be hardened during the heat treatment process. It reduces corrosion resistance and makes steel fragile.
Chrome (Cr): strongly increases the corrosion resistance of the steel and, at some level, increases its hardness.
Manganese (Mn): improves the structure of the steel and increases the possibility of a larger hardening of the steel.
Vanadium (V): the key element to increase the hardness of the steel. This increases the possibility of having a sharper blade and keeps sharpness longer.
Molybdenum (Mo): increases corrosion resistance, is often present in stainless steels and helps maintain the hardness and power of steel in the event of a temperature change.
Silicon (Si): increases the positive effects of carbon (C). This increases the hardness and power of the steel.
Cobalt (Co): for greater hardness and corrosion resistance.
Tungsten (W): significantly increases the wear resistance of steel.
Phosphorus (P): impurity present in small amounts in all types of steel.
Soufre (S): impurity present in small amounts in all types of steel.
The Japanese sword represents traditional Japanese craftsmanship. Made of Japanese steel with iron sand as the raw material, the edge of a Japanese sword is well known around the world. Hitachi Metals Co., Ltd. produces Yasuki steel from raw materials for Japanese steel. In the past, iron sand with a high degree of purity could be excavated in the mountains of Tottori and Shimane prefectures and was refined to become Tama Hagane using a traditional treatment (Tatara). Hitachi further improved its techniques by establishing its Yasuki steel manufacturing plant. Steel is called blue steel, white steel and yellow steel in order of quality. These names would be derived from the fact that blue and white papers were used to package the finished steel for identification purposes.
They can only be made by a few skilled craftsmen in Japan using the same method as the traditional Japanese sword. It is an art to work with traditional Japanese techniques, with exceptional sharpness and durability. Production is very small, due to the difficulty and tedious process. To have a few, these knives are amazing. Whether you are a collector or just a fan of Japanese kitchen knives, it is a must. Expensive, of course, but when you understand the essence of the work for the manufacture of this object, you realize that the price is only just compensation in front of this masterpiece.
High-carbon steels are the preferred choice of Japanese chefs. Because of their high carbon content (C), these steels can be forged with high hardness (60 degrees HRC) while being very easy to re-sharpen. High-carbon steel knives require special attention during maintenance, wiping them after each use, oiling the blade from time to time, and developing a patina over time. Poor maintenance will develop corrosion.
Japanese blacksmiths have always chosen steel with care. Traditional katana is made from tamahagane steel, produced only in western Japan. Traditional Japanese steel is made using similar techniques. This steel is used in the manufacture of knives subjected to processing processes similar to those of katana. There are two main types of steel: shiro-ko (white steel No. 1, No. 2) and ao-ko (blue steel No. 1, No. 2 and Aogami steel).
White steel is an extremely pure steel with a high percentage of carbon and no additional ingredients (it may contain phosphorus (F) and sulphur (S) as impurities). There are two types of white steel: white steel 1 and white steel 2. Forging white steel is extremely difficult and requires highly skilled craftsmen. A knife made from this steel has an extremely sharp edge, but it is fragile and susceptible to cracking.
White steel No.1 contains iron (Fe), carbon (C) 1.25-1.35%, manganese (Mn) 0.20 to 0.30%, phosphorus (P) to 0.03%, sulphur (S) to 0.004% and silicon (Si) to 0.10 to 0.20%. It is very popular with professional chefs who prepare traditional Japanese cuisine, as it can be refined to get an extremely fine edge. It has a very good cutting fit and is easy to re-sharpen.
White steel No.2 contains iron (Fe), carbon (C) 1 – 1.15%, manganese (Mn) 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%. It has a minimum of impurities and a very fine grain structure, so it is ideal for fine cutting tools such as traditional Japanese style knives. It also has a very good cutting retention and very easy to re-sharpen. Recommended for new users of traditional Japanese knives.
If we add chrome and tungsten to extremely refined white steel, we get blue steel. Thanks to additives, blue steel is more durable, slightly more resistant to corrosion, but more importantly, it has a better “kirenaga”, a Japanese word for duration and sharpness. Blue steel knives are mainly used in Japanese restaurants, where the chef needs a knife that stays sharp for a long time.
Blue steel No.1 contains iron (Fe), carbon (C) 1.25 – 1.35%, chromium (Cr) 0.20 – 0.50%, manganese (Mn) 0.50% 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%. The extra carbon and tungsten further improve the preservation of cutting hold and tenacity. This steel is perhaps most often observed in traditional Japanese knives of high quality with simple edge.
Blue steel No.2 contains iron (Fe), carbon (C) 1.05 – 1.15%, chromium (Cr) 0.20 – 0.50%, manganese (Mn) 0.20 – 0.3 0%, phosphorus (P) 0.03%, sulphur (S) 0.004%, silicon (Si) 0.10 – 0.20% and tungsten (W) 1.00 – 1.58%. Many chiefs have noted that this steel is very similar to white steel No.2 in terms of sharpness of the edge. However, it has a slightly higher edge retention.
Contains iron (Fe), carbon (C) 1.40 – 1.50%, chromium (Cr) 0.30 – 0.50%, manganese (Mn) 0.20 – 0.30%, molybdenum (Mo) 0.30 – 0.52% and phosphorus (P) 0.03%, sulphur (S) 0.004%, silicon (Si) 0.10-0.20%, tungsten (W) 2.00 – 2.50% and vanadium (V) 0.30 – 0.50%.
It is one of the largest Japanese carbon steels in terms of performance. In addition to containing more carbon, chromium and tungsten than Blue Steel No.1, it also includes molybdenum. It has very good sharpness and excellent sharpness. It is also able to achieve high hardness without being brittling. As a result, many knife enthusiasts rank super aogami as one of the best high-carbon steels in the world.
By adding chromium (Cr) to the steel, we increase its corrosion resistance. Chromium oxide forms a protective film on the surface of the steel, which prevents any contact between iron and water or oxygen. If the base steel alloy contains 12% or more chrome, we call it stainless steel. Even stainless steel kitchen knives should be wiped and dried after use, especially if you cut fruits and vegetables containing acids (lemon, onions, tomatoes, etc.). If we leave the knife dirty and moist for a long time, even stainless steel can corrode.
As a result of technological development, we have seen the emergence of new types of steel, which combine the quality of steel with a high percentage of carbon and the practicality of corrosion-resistant steel. High-carbon (C) and corrosion-resistant steels are now highly valued by professional chefs.
(Special Steel Takefu Co., Ltd.) is a high-quality, high-carbon Japanese stainless steel, popular for making cutlery. It has good corrosion resistance, good sharpness and sharpness. The rockwell’s hardness is also relatively high.
It represents the best of the supply of corrosion-resistant steel. It contains iron (Fe), carbon (C) 0.95 – 1.15%, chromium (Cr) 14.50 – 15.5%, cobalt (Co) 1.30 – 1.50%, manganese (Mn) 0.50%, molybdenum (Mo) 0.90 – 1.20%, phosphorus (P) 0.03% and vanadium 0.10-0.3%. It is one of the most popular and reputable Japanese stainless steels. It has a high corrosion resistance and can provide very good cutting sharpness and good sharpness. The VG-10 belongs to the group of steels called “cobalt steels”, but it also contains vanadium, which improves its strength and tenacity.
Known as Ginsan-ko or silver no.3, containing iron (Fe), carbon (C) 0.92 – 1.10%, chromium (Cr) 13.00 – 14.5%, manganese (Mn) 0.60 – 1.00%, phosphorus (P) 0.03%, sulphur (S) 0.02% and silicon (Si) 0.35%. It is a very fine-grained stainless steel that can achieve sharpness and cut retention comparable to some high-carbon steels. It has even been used to create corrosion-resistant versions of traditional Japanese single-edged knives. It is very popular with professionals and cooks. It is generally considered slightly easier to sharpen than the VG-10. A favorite steel in this section. Its hardness is well balanced 60-61 HRC (in general).
Tamahagane is considered the mother of all steels. This was the case in the past, or it always is when we talk about Japanese katanas and swords, but modern science produces new special steels, much more suited to kitchen blades, such as powdered steels. Such steel is more advanced, harder, sharper and has one thing in common with the old tamahagane: they are both made in Japan! Japanese high-tech steel is forged the old-world by the same families of blacksmiths who made katanas. It is the best fusion of the old and the modern to produce the best knives or better, the sharpest!
Steels for metallurgy powders, are steels often used in industrial applications that require tools capable of cutting steel and withstand extreme forces and temperatures. Powdered steels are made using a different manufacturing process, resulting in richer chemical ingredients and a very fine grain structure with excellent metallurgical properties.
Knives made from these steels are rare, difficult and expensive to produce, and only the best cutlers are able to forge, laminate and heat-process them. It is a very difficult process that requires a lot of experience, knowledge and a perfectly inclined blacksmith. The steel knives of properly manufactured powders are among the elite kitchen blades.
Very high hardness up to 67 on the Rockwell C scale (HRC) and good tenacity.
Satisfactory corrosion resistance.
Easy to sharpen steel, with a fine microstructure for a fine edge and the ability to stay sharper longer than other traditional steels.
Metallurgy of “super steel” powders. It has a chemical composition similar to that of Cowry X and offers a similar level of performance. Unfortunately, due to the difficulty of producing ZDP-189 and special forging and thermal treatment, few blacksmiths are able to process it.
Obviously these knives are very expensive.
C 3.00% Cr 20.00%
It is also a “super steel” metallurgy powders. Became one of the most popular steels due to its cutting performance, excellent sharpness and high corrosion resistance. Unlike Cowry X and ZDP-189, R2 steel kitchen knives are much more available on the market.
C 1.25-1.45% Cr 14.00-16.00% MO 2.3-3.3% V 1.8-2.2%
It is a “super steel” metallurgy powder from Hitachi Metals Ltd. Its rich chemical composition and fine microstructure make it possible to produce knives that have an exceptional balance between hardness and its preservation of the edge.
C 1.27-1.37% Cr 3.70-4.70% W 5.60 to 6.40% MO 4.60-5.40% V 2.80-3.30% Co 7.50-8.50%
It is a “super steel” metallurgical powders high in carbon and chrome. Unfortunately, it is expensive and technically difficult to use for cutlers. These beautiful knives are therefore rather rare.
C 3.00% Cr 20.00% MO 1.00% V 0.3%
I hope this article was able to illuminate your lanterns and elucidate the riddles about steels. I really wanted to write about it, since the choices are many and can be difficult, especially when buying a new knife. This article does not fully summarize all types of steels, it is mainly those that are currently on the market.
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