Types of Japanese steels

Steel is a topic that can be debated for hours if not days when two connoisseurs meet. However, extensive information about him can quickly tire and become extremely boring for a person who just wants to know why the old, slightly orange-grey knife in grandma's drawer remains forever sharp. In order to answer this question, we will make a small division and go back a few years.

For a piece of metal to be called steel, it must contain two things: iron and carbon. These are the two basic ingredients used in steel production. Over time, people have learned that if they add other chemical substances to the recipe, they can easily affect the characteristics of steel.

The higher the percentage of carbon in the steel, the more prone it will be to rust, the positive side is that the steel will be stronger and therefore hold the blade much longer. In 1913, the first stainless steel was made by adding chromium, and since then, stainless steel technology has been developing.

Until a few years ago, stainless steel was considered extremely bad for making knives, it was almost impossible to sharpen, and it would lose its sharpness the same seconds you tried to cut something. Here is the answer to the question about the grandmother's knife, then carbon steel ( rusting ) was used for its production. Many Japanese knives are still made of rust steel today, it has been that way for centuries and will remain so for at least some time to come. Their master blacksmiths firmly defend the position that ideal performance is achieved in this way. The best stainless steels are produced by the Japanese company Hitachi and they are Tamahagane, Aogami, Shirogami and Yellow steel. These knives are extremely easy to sharpen, they dull very slowly and the level of sharpness is high, in return they require the user to clean them and store them properly after use.

The technology of stainless steel production has advanced to such an extent that today we have steels that behave in all aspects almost identically to stainless steels, achieve exceptional hardness, can be sharpened easily, quickly and well. Make no mistake, these steels still have a high percentage of carbon (high carbon stainless) like stainless steels, however, the difference is that they have added components that prevent rust stains from appearing on them. The most famous representatives of these steels are: SG2/R2, Ginsan, SrS15, VG10, VG1, AUS8 and ZDP steel. If you want the best of them, you'll have to shell out a bit more money than you'd expect for a kitchen knife, but it's worth every penny.

We will briefly mention the third, not so popular group of semi-reactive steels that can also be found in Japanese knives. These steels are exactly on the border between the two types mentioned above and often their price is more acceptable than stainless steels, and their performance is more similar to stainless steels. The most famous steels of this type are Cromax, HAP40, SLD and VS1.

Below we will talk about the most popular steels used to make Japanese kitchen knives.

STAINLESS STEEL

Rust can appear on every steel, without exception, but we call this group stainless because components have been added to them that increase the steel's resistance to oxidation, so it is very difficult for these steels to rust even in extreme conditions.

VG10

VG10 steel is produced by Takefu Special Steel and this steel is specially designed to be perfect for making kitchen knives. Many large manufacturers in Japan, such as Tojiro and Shun factories, have chosen this steel when making their knives. It has also taken a high place among individual blacksmiths, especially after the popularization of stainless steels in the world of kitchen knives. VG10 reaches a hardness of 61HRC after hardening, belongs to the stainless steels and is known for its wear resistance, excellent blade retention and said hardness. VG-10 steel is characterized by extremely slow wear, so these knives, with proper sharpening, will remain in your use for a lifetime.

SG2

Super Gold 2 or R2 is another steel that comes to us from Takefu Special Steel . It represented a real discovery in the world of knives, and today it is the most valued stainless steel on the market. SG2 is produced by powder technology, that is, by dissolving small steel particles in specially controlled conditions, which results in an extremely clean product with a high percentage of carbon in it. SG2 has more carbon than some carbon steels, yet it is stainless which makes it perform perfectly and requires no extra maintenance. It sharpens easily and loses its sharpness slowly. Knives made of this steel are extremely sharp but also delicate, so use it properly so that it does not chip . SG2 achieves a hardness of 63 degrees on the Rockwell scale after the hardening process.

VG1

Also a product of the Takefu Special Steel company from Japan, VG1 is another very interesting and good steel. Knives made of this steel are hardened to 60HRC, which is only a few degrees higher than German knives. This makes them extremely suitable for users from our area who would like to have better steel than what they are used to. The technology by which it was produced proved to be very successful and it was from this steel that the rest of the VG family originated. It is characterized by a very high degree of cleanliness, very high resistance to wet conditions and, most importantly, a long life of sharpness. This latter is the decisive factor why this is the favorite steel for some.

Ginsan

Ginsan comes to us from the Hitachi steel company, it is an exceptional steel that is very similar in structure to the best Hitachi products like Super Aogami steel, with one big difference - Ginsan is a non-hardening steel! Knives made of this steel do not require special maintenance. Its characteristics are greatly improved by the forging process, and it is especially valued in the Sakai region of Japan. After hardening it reaches a hardness of 60-63HRC which ensures that once sharpened the blade stays sharp for a long time.

ZDP-189

This steel is also manufactured by the Hitachi company, but there are a few things that set it apart. It is produced in powder technology like SG2 or R2 steel, but the chemical composition is significantly different. ZDP contains 3% carbon and 20% chromium, which is more than any other steel. This results in the following characteristics: ZDP is an extremely hard steel that after hardening measures 67HRC, the high percentage of chromium means that this steel, although extremely rich in carbon, is stainless. This combination is not common, but it is possible. In addition to the above, it is important to say that ZDP has an incomparably greater degree of resistance to abrasive action, which means that it is very, very demanding for processing and sharpening. Even in the production process itself, the blade is so difficult to sharpen that a large number of blacksmiths avoid it for this very reason. This is particularly important for the user because he can expect that if he does not buy a knife in this steel from a proven manufacturer, he can get a product of different quality. Also if you intend to maintain these knives yourself, you will need a diamond tool, a lot of time and patience because it is extremely difficult to achieve good results. Knives made of this steel in theory keep their sharpness for a very long time, while in practice it is a somewhat different experience.

AUS6, AUS8 and AUS10

The AUS steel family comes to us from the Aichi Steel company based in the Japanese city of Tokai. These steels are included in the class of medium to better steels, and they are interesting to manufacturers because of their attractive price, ease of processing and resistance to rusting. There are 3 types of AUS steel: AUS6, AUS8 and AUS10. Each of the above differs in chemical composition, of which the main difference is in the carbon content, and the best quality is AUS10. Due to their price, they are widely used in the production of factory knives, which can be purchased somewhat more favorably than hand-forged ones. After hardening, they reach a hardness of 58-59 HRC, they can be sharpened well and there is no doubt that they will serve well as steel for kitchen knives.

CARBON (RUSTING) STEELS

The first steel that was made was carbon illite rust steel. You can often find them under the name " carbon steels " and this refers to the fact that the carbon that was added during production is completely exposed or unprotected from external factors, and this primarily means moisture. It is due to the reaction of carbon with water that the oxidation process takes place and a whole spectrum of rainbow colors can appear on the blade.

AOGAMI

Aogami " blue " steel is often considered the best steel for making kitchen knives. It belongs to rusting steels and you must take care to wash and dry the knife thoroughly after use. With proper maintenance, it will create a protective layer (patina). Aogami is produced by the Japanese company Hitachi and comes under the designations: Blue no. 2, Plavi no. 1, and Super Blue steel, and the difference between them is the carbon content (super aogami contains the most, as much as 1.5%) Aogami can be tarnished in oil and in water, and reaches a hardness of 64 HRC, which is exactly why it is a favorite among blacksmiths. This is believed to be one of the purest and highest quality steels known to man, and knives made from it are said to cut like a dream!

Shirogami

Shirogami " white " steel is another Hitachi product. The extremely pure structure of this steel brings it into line with the ancient Tamahagane Japanese steel, which is believed to be the best ever produced. White steel makes ideal traditional knives such as Ynagiba and Usuba. It can be tarnished exclusively in water and requires exceptional performance and knowledge of steel processing technology from the forging master. It belongs to the rusting steels and since there are no additives to protect it, it is necessary to thoroughly and regularly maintain the blade. Shirogami appears under the labels: White no. 3, White no. 2 and White no. 1, of which White No. 1 has the highest carbon content and that is also the only difference. It reaches a hardness of 64HRC and is characterized by a strong "bite" of the blade.

Yellow steel

The company Hitachi from Japan produces a lot of different steels, among them is yellow steel. This is the rusting steel used to make knives in the lower price range. Unlike the similar " white " steel, yellow steel has slightly more impurities, hence the better price. However, this steel reaches 61 degrees on the Rockwell hardness scale, which is much higher than all European knives and even some Japanese knives. Knives made of this steel should be properly wiped after each use in order to create an even protective layer (patina). This steel has found its best use in the production of traditional, one-sided sharpened knives.

Tamahagane

Finally, we must mention Tamahagan. This famous steel was once produced throughout Japan and was used to make the finest blades known to man. The production process is so exhaustive and complicated that it requires the continuous engagement of several people for several days. Today, only the Hitachi company makes this steel once a year in order to save the tradition from being forgotten. All produced quantities are reserved for precisely specified manufacturers of razors, katanas, knives, scissors and other traditional Japanese tools. You must be thinking, which are the specific manufacturers? The answer is, those manufacturers whose skills are recognized by the Japanese government as a cultural asset of Japan. Because of all the above, the government has banned the export of this steel outside of Japan, and owning items made of it is considered a real luxury. Tamahagane is the purest steel known to man and that is why it is believed to have special characteristics that give it perfect sharpness.

SEMI-REACTIVE STEELS

Semi-reactive steels are used to make knives, and the idea is to get the best of both worlds. Professionals love these steels because they are right on the edge in terms of low maintenance, while retaining qualities like ease of sharpening, sharpness retention and overall performance.

Cromax

Cromax steel is one of the main representatives of this category. It is produced in the Takefu Special Steel company. The most important advantage of this steel is its hardness, which reaches an incredible 65 HRC. This ensures that the knives stay sharp for a very long time, which can be a crucial feature for some users. All semi-reactive steels, including Cromax, will change color very quickly when they come into contact with extremely acidic foods such as citrus or onions, however, in other situations, the oxidation process takes place much slower than with carbon knives and does not require a lot of maintenance time. This steel tends to form a protective layer or patina that gives it a unique appearance, and it is very difficult to get it to actually rust.

SLD

SLD steel is manufactured by Hitachi in Japan and is considered a semi-reactive steel. Initially, this steel was designed for the production of tools for cutting other steels in a relaxed state. Knifesmiths in Japan have come to love it because of the specific structure it gets during the tempering process. Namely, the carbide crystal formations are extremely large, which makes this steel take on "aggressive" performance after sharpening. Large crystals are very good when cutting foods with skin like eggplant, tomatoes or even for cutting large pieces of meat. These steels have the ability to self-sharpen, and are especially valued for making Sujihiki knives.

HAP steels

The HAP steel family belongs to the semi-reactive steels and is produced by the Hitachi company. There are many variations of this steel and they are indicated by the numbers that come after the name, so we have: HAP40, HAP10, HAP50, HAP72, HAP5R. HAP40 and HAP10 are most often used for kitchen knives. This steel has an exceptional hardness of 67HRC, but do not forget that it is semi-reactive and that you must clean it after use, especially if you prepare acidic foods.

CONCLUSION

The most important steels used to make Japanese kitchen knives are mentioned. We're sure to have left out some lesser-used steel, but these brief guidelines should help you discover the perfect product for you.