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Terminology clarification again. Since we already know that all steels are Carbon steels strictly speaking, under the term Carbon Steels I refer to the steels with no, or very low stain resistance.

Common note for Aogami 1, Aogami 2, Shirogami 1 and Shirogami 2 steels

- All the steels listed are produced in two versions, Type A and Type B, where type A has higher carbon compared to average spec, they are designed for forgers, to compensate for the loss of carbon during forging, type B is more common for stamped or CNC cut knives. Thanks to Shinichi Watnaabe for providing the exact info.

Aogami(Blue) 1 (YSS)

 - Also referred as Ao-Ko, or Ao-ichi-ko, where ichi is one in Japanese and ko is steel. Hitachi high carbon steel(C 1.3%-1.4%), very pure(P <= 0.025%, S <= 0.004%) specifically developed for tools and knives. Ref - Aogami 1 Steel Composition. In my experience - very good steel, and very popular choice for high end Japanese kitchen knives. A lot of Japanese custom makers use it. Takes very fine edge, and holds it long time. Easy to sharpen, even at 65HRC. Slightly better wear resistance compared to Aogami(Blue) 2, however slightly less tough compared to it. I have several kitchen knives in this steel: Watanabe Honyaki Gyuto, Nakiri and others. Takes patina easily, but just wiping it clean during cutting and washing after using it, prevents rust completely.
Ref - Aogami 1 vs. Aogami 2 vs. Aogami Super steels composition comparison chart.
Ref - Aogami 1 A steel composition, Aogami 1 B steel composition.

Aogami(Blue) 2 (YSS)

 - Also referred as Ao-Ko II. Hitachi high carbon steel, specifically developed for tools and knives. Ref - Aogami 2 Steel Composition. Very pure alloy - P <= 0.025%, S <= 0.004%. In my experience very good steel, just like its brother Aogami 1. As mentioned above, it's slightly tougher compromising wear resistance a bit. Although, at those levels of hardness 63HRC and above, the difference is really hard to tell, at least in home kitchen use. Watanabe makes his Honesuki knives out of Blue 2, one of my favorites, Kumagoro Gyuto is also made out of it. Aritsugu also makes his high end knives from blue 2, I have only very positive experience with his Honkasumi Yanagi and Fugubiki, both blue 2, 65HRC+.
Ref - Aogami 1 vs. Aogami 2 vs. Aogami Super steels composition comparison chart.
Ref - Aogami 2 A steel composition, Aogami 2 B steel composition.

Aogami(Blue) Super (YSS)

 - Hitachi high carbon steel, specifically developed for tools and knives. Aogami Super Steel Composition. Another solid performer from Aogami family. This one has highest wear resistance and lowest toughness of three. I have Takeda Chukabocho(cleaver) and Takeda Deba in Aogami super. Both knives exhibit very good edge holding, and Deba is just fine crushing chicken bones. Both knives are hardened to 61HRC. Later on I've acquired Moritaka Chukabocho, also Aogami Super steel, hardened to 65HRC. Edge holding is just outstanding and even though it has really hefty, 230mm long, 112mm wide blade, with 10° per side edge, never had a single chip on it in more than two years. Ref - Aogami 1 vs. Aogami 2 vs. Aogami Super steels composition comparison chart.

Kigami 2 (YSS)

- Better steel compared to JIS KS series, but worse than both, Aogami and Shirogami. Used in high end tools and low/mid class kitchen knives. Ref - Kigami 2 Steel Composition.

Kigami 3 (YSS)

- Very similar to Kigami 2, with less Carbon. Ref - Kigami 2 vs. Kigami 3 Steel Composition Comparison.

SK3

- Solid performer as a cutlery steel, Tsukiji Masamoto uses it in his Carbon steel kitchen knives. Ref - SK3 steel composition.

SK4

- Low grade steel, mainly due to impurities. Used mainly in hand tools like axes and hammers. Can be found in cheap kitchen knives as well. Ref - SK4 steel composition.

SK5

- Similar to SK4, with even less Carbon. SK3 vs. SK4 vs. SK5 steel composition comparison.

O1

 - Similar to 1095 and Aogami steels by makeup. Gets very hard and has very good edge holding ability. As far as I know several custom knife makers produce kitchen knives out of this steel. Good choice, no resistance to corrosion obviously. L.R. Harner aka Butch works with O1 kitchen knives. Ref - O1 steel composition.

Shirogami(White) 1 (YSS)

 - Also referred as Shiro-Ko 1 or simply Shiro-Ko. Identical to Blue 1, except for the absence of Cr and W. So, it's pretty much very pure carbon steel. Takes very fine because of this. Very popular knife steel for high end Japanese cutlery and especially with Honyaki type blades. Very good edge holding, very high working hardness, 64-65HRC.
Ref - Shirogami 1 steel composition, Shirogami 1 A steel composition, Shirogami 1 B steel composition.

Shirogami(White) 2 (YSS)

 - Also referred as Shiro-Ko 2 and Shiro-ni-ko. Same as Shiro-Ko 1, except slightly lower C content. Very good edge holding, very high working hardness, 64-65HRC.
Ref - Shirogami 2 steel composition, Shirogami 2 A steel composition, Shirogami 2 B steel composition.

Shirogami(White) 3 (YSS)

 - Also referred as Shiro-Ko 3. Same as Shiro-Ko 1, except contains C - 0.8%. Good edge holding, gets very high hardness. Not too tough. Haven't seen any knives in Shirogami 3 so far. May be used in tools like chisels. Ref - Shirogami 3 steel composition.


* YSS stands for Yasuki(sometimes Yasugi) Specialty Steel.

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Last updated - 09/16/11