Knife Steels

There are hundreds of different steels in the market. When it comes to steel performance, various steel properties come into play. Edge retention, stain resistance, toughness are only few to mention and all play a significant role in overall knife performance in the kitchen. Without overanalyzing, we will give a simple and conclusive guide about the most famous steels used in Japanese knives and what you should expect from each steel.

Common steels used in Japanese knives can be categorized in 3 main categories:

High Carbon steels (Non stainless)

  • Shirogami 1 (White 1) : Very famous among Japanese kitchen knives as it is very pure and takes the finest edge among the Aogami and Shirogami steels and gives impressive cuts. It hits high numbers in the Rockwell scale, holds a good edge for low alloy steel and sharpens easily, it is very reactive (it will rust if not maintained) so this one needs high maintenance. It has the same profile as Blue 1 but without the Chromium and Tungsten.
  • Shirogami 2 (White 2) : Essentially the same steel as Shirogami 1 but with less Carbon. It can achieve almost the same hardness and take excellent thin edge, a little bit tougher than Shirogami 1 and also very pure, as white 1.
  • Shirogami 3 (White 3): Same steel as Shirogami 2 but with less carbon. You may notice that the higher the reference number of the series, the lower the carbon that means lower attenable hardness and less edge retention but increased toughness!
  • Aogami 1 (Blue 1): Another famous steel from the Aogami series, it is an excellent choice for kitchen knives. As expected, it is not stainless and it can take a very fine edge and achieve high hardness that helps in edge stability and wear resistance. It is easy to sharpen and can take razor sharp edge in matter of minutes.
  • Aogami 2 (Blue 2): The second one of the Aogami series and essentially the same as Aogami 1. It is a little bit tougher but also less wear resistant and edge holding.
  • Aogami Super (Blue super): Probably the most well-known among the Aogami steels. This steel takes amazing edge, hits high HRC numbers and holds a great edge (the best wear resistance in the Aogami series). It is the less tough of the series and requires great attention in cutting and in maintenance.

As a conclusion, Shirogami steels take the best edge with Shirogami 1 to be the champion Shirogami 3 being the toughest. The Aogami steels have better edge retention than the Shirogamis with Blue super being the most wear resistant and Blue 1 being the most tough!

Interesting note: Both Shirogamis and Aogamis steels are named White or Blue from the white or blue tags attached to them when sent to the blacksmiths.

 

Stain resistant alloy steels (stainless)

  • VG – 10 : One of the most famous steels in the knife world. It is a corrosion resistant steel (stainless) that takes a very sharp edge. Due to its high hardness it can hold a good edge but it is also prone to chip as toughness is not too high.
  • Ginsan: A similar steel to VG-10 although a little bit simpler. Has similar amounts of carbon and chromium and it was designed for cutlery industry.

Powder Metallurgy Steels (both stainless and stain resistant)

Powder Metallurgy is a manufacturing method that uses a special procedure and makes the final grain of the steels very homogenous, pure and fine. It helps in wear resistance, toughness, hardness and more.

  • SG-2 (R2) – An exceptional steel that has a great balance between edge retention, stain resistance and sharpness. It has an amount of Vanadium that makes it fairly wear resistant and enough chromium to make it essentially stainless.
  • ZDP – 189 – The king of Japanese steels edge retention. This steel has immense carbon amount (3%) so can achieve amazing hardness (64-67 HRC) and keep a razor-sharp edge for a very long time. It has great amount of chromium but it is not stainless, most of that chromium bonds with carbon and forms chromium carbides that contribute to wear resistance. When it comes to resharpening needs patience and experience. Due to its high hardness and high carbide volume, the steel needs care and careful use otherwise it can chip easily.
  • Cowry X – Essentially the same steels as ZDP 189. It has the same amount of carbon and chromium so it hardens in the same values and forms almost the same amount of chromium carbides that help in wear resistance. As in ZDP 189, it is difficult to sharpen and chips easily in high hardness.
  • HAP – 40 – A tough PM steel that has great amount of Vanadium and tungsten, two of the greatest carbide formers, so it will show some great wear resistance properties. It has low amount of chromium so it is not stainless but also has molybdenium that helps in corrosion resistance, so it is somewhat semi stainless.

Please note that hardness plays a role in overall performance of a knife. In general, the harder the steel (better edge retention) the less tough it is (more prone to chipping). Hardness is only an indication and varies between steels ex. You can’t compare a ZDP 189 in 64hrc and a Shirogami in 64hrc in terms of edge retention. Also please note that cutting ability (thickness behind the edge, spine thickness etc) plays a significant role as to how a knife performs.

*Carbides:  Hard particles that for between carbon and other elements. They contribute greatly in wear resistance but in great amounts can reduce toughness in a steel. Powder Metallurgy (PM) process helps in reducing the size of these carbides and thus improve toughness while maintaining high wear resistance