About Japanese Steels
When you are looking for knives made with Japanese heat-treated steel, you are always talking about the internal metal which composes the cutting blade. Most Japanese style commercial knives are clad in either a stainless or carbon steel which is significantly less hard, and as such less brittle. This helps absorb the impact of the blade traveling through the hard and brittle core steel, keeping it from chipping or cracking. If you are shopping for a Honyaki knife, where the stele itself has been forged in a manner which leads to the spine being a lower hardness than the edge (fundementally replacing the need for cladding), the whole knife will be one steel type.
Each steel has a hardness range it can be forged into. The skill of the blacksmith determines how hard the knife will be, though higher hardness is not always what the blacksmith is shooting for. This hardness is represented in HRC (Rockwell Hardness Scale). Stainless Steel or lower heat-treated Carbon Steel knives tend to be around 56-58 HRC, while Japanese steel knives start being in the 60+ range.
There are a range of different steels used in Japanese style knives. I will cover both proper Japanese steel types as well as some which are often used but may not actually be of Japanese production. What you pick will depend upon your application, sharpening intentions, and how concerned you are about the knife rusting or keeping its edge as long as possible. The steels will be divided into different categories: Carbon (below 12% Chromium and thus prone to rusting), Corrosion-Resistant (above 12% Chromium and less prone to rusting, e.g. Stainless Steel).
Japanese Razor Steel is much harder to come across information for.
Carbon vs Stainless Steel
Japanese Knife Steel Types [Carbon]
Shiro-Ko | Shirogami | White Steel | White Paper Steel – 白紙
Producer: Hitachi Metals
Variants:
- White #1 – Iron (Fe), carbon (C) 1.25 – 1.35%, manganese (Mn) 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%
- ~61-64 HRC
- White #2 – 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%
- ~60-63 HRC
- White #3 – N/A
- ~60 HRC
Most commonly referred to as White #1, White #2, etc. This name comes from the white paper the steel is wrapped in when it comes from the factory. White steel is a very traditional steel which has been made for a long time. Both are extremely pure with only a minor number of impurities. White #1 has the higher HRC possibility, though it is very brittle so many people prefer White #2 which will perform similarly but its lower Carbon content allows it to be more forgiving. White steels get their strength from their fine grain pattern and the iron carbides formed during forging.
Ao-Ko | Aogami | Blue Steel | Blue Paper Steel – 青紙
Producer: Hitachi Metals
Variants
- Blue #1 – Iron (Fe), carbon (C) 1.25 – 1.35%, chromium (Cr) 0.20 – 0.50%, manganese (Mn) 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%
- ~63-65 HRC
- Blue #2 – Iron (Fe), carbon (C) 1.25 – 1.35%, chromium (Cr) 0.20 – 0.50%, manganese (Mn) 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%
- ~62-64 HRC
- Blue Super (青紙スーパ) – Iron (Fe), carbon (C) 1.25 – 1.35%, chromium (Cr) 0.20 – 0.50%, manganese (Mn) 0.20 – 0.30%, phosphorus (P) 0.03%, sulphur (S) 0.004% and silicon (Si) 0.10 – 0.20%
- ~65-67 HRC
Most commonly referred to as Blue #1, Blue #2, or Blue Super. Similarly named for the blue paper which is wrapped around the steel when it comes out of the factory. These are considered a refined White Steel, with the addition of minor amounts of Chromium and Tungsten. The addition of Chromium in this case allows for a bit more resistance to rust, but it is nowhere near the levels needed for stainless. As we see with the HRC compared to Shirogami, the Tungsten also increases the HRC across the board. Compared to White Paper steel, they should keep their edge longer due to the increased hardness but will be more difficult to sharpen and more prone to chipping or cracks. Blue paper steel not only get their hardness from their fine grain pattern and iron carbides, but also additional carbides formed by the inclusion of chromium and tungsten. These carbides are tougher lending to the greater HRC when compared to White paper steel but also larger than the iron only carbides, making the blades less flexible by comparison.
Yellow Steel | Yellow Paper Steel – 黄紙
Japanese Knife Steel Types [Corrosion-Resistant]
VG-10
Producer: Takefu Specialy Steels
Variants
- VG-10 – 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 (V) 0.10-0.3%
- ~58-61 HRC
This is the most commonly highly corrosion resistant steel on the market, and the one which will endure water mistreatment the longest. It is also one of the cheaper steels on the market to make knives out of as it does not require traditional forging, but instead can be produced in large sheets which are then fabricated into the appropriate shape for its application. After it is in its final shape, the metal is then hardened in an electric furnace.
Ginsan-Ko | Ginsan | Silver Steel – 銀三鋼
Producer: Hitachi Metals
Variants
- Silver #3 – 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%
- ~58-61 HRC
The most common stainless steel which Hitachi produces, it performs similarly to VG-10 but requires traditional forging and is less corrosion resistant due to its lower Chromium content. Due to the traditional forging, it is able to achieve the same HRC as VG-10 without the need for cobalt, making it a bit easier to sharpen in comparison.
SG2 | Super Gold 2 | R-2
Producer: Takefu Specialy Steels
Variants
- Super Gold 2 – Iron (Fe), carbon: 1.25 – 1.45%, vanadium: 1.80 – 2.20%, chromium: 14.00 – 16.00%, molybdenum: 2.30 – 3.30%, manganese: .40%, phosphorus: .03%, sulfur: .03%, silicon: .50%
- ~61-64 HRC
The SG2 variant is made by Takefu while you will see R-2 versions of the medal made by Kobelco. It is believed they are the same and as such can be used interchangable. This is the most commonly available Powdered Metturalgy (PM) steel and the only one worth putting on this list at the time of creation. It has good corrosion/rust resistance and keeps the best stainless steel edge outside of other difficult to find PM steels. Due to its HRC it may be more difficult to sharpen than other stainless options.
19c27 | Sandvik Steel | Swedish Steel
Producer: Sandvik
Variants
- Swedish Steel – Iron (Fe), carbon (C) 0.95%, chromium (Cr) 13.5%, manganese (Mn) 0.70%, phosphorus (P) 0.03%, sulphur (S) 0.01% and silicon (Si) 0.40%
- ~55-63 HRC
This is not a Japanese produced steel but is extremely popular amongst Japanese knife producers.
Razor Steel Types [Carbon]
Swedish Steel
Producer: Sandvik
The vast majority of Japanese razors are made of this type of steel as at the time no high production Japanese steel suitable for straight razors was in production. This is different than the modern “Swedish Steel” mentioned above for knives, as it is not stainless and of a different composition. As yet, I have been unable to track down the exact specifications of the steel. If the Japanese razor does not specify it is Yasuki or Tamahagane steel, it is made from Swedish Steel.
Yasuki Steel
Producer Hitachi Metals
Often called “Tamahagane” or “Masa Steel”, this metal was developed between Hitachi Metals and renowned razor blacksmith/sharpener Iwasaki. The process of making this material utilizes smelting iron-sand ore similar to the traditional method for sword making. It is a different metal than the Tamahagane used for swords though, however it is extremely pure similar to traditional Tamahagane. It is still produced but not in large quantities due to its labor-intensive nature which makes it quite expensive. This is sometimes compared to White #1 as it has very similar properties.
Other Kanji
ステンレス – Stainless
玉鋼 – Tamahagane
鋼 – Hagane – Carbon Steel
鉄 – Tetsu – Iron
本焼き – Honyaki
