Aogami (also known as Blue Paper Steel or Blue Steel) is a legendary high-carbon steel produced by Hitachi Metals in Japan. It belongs to the "YSS" (Yasugi Special Steel) family and is one of the most prestigious steels used in traditional Japanese kitchen knives and woodworking tools.
The name "Blue Paper" comes from the simple fact that Hitachi wraps this specific steel in blue paper for identification at the factory.
Key Characteristics
Legendary Sharpness: Aogami is famous for its ability to take a "scary sharp" edge. Because of its purity and fine grain, it can be sharpened to a more acute and aggressive edge than almost any stainless steel.
Extreme Edge Retention: Compared to its sibling, Shirogami (White Steel), Aogami contains added Tungsten and Chromium, which form hard carbides. This allows it to stay sharp for a significantly longer time.
High Hardness: It is typically heat-treated to an immense 61–65 HRC.
Non-Stainless (Highly Reactive): Aogami is not stainless. It will rust and stain very quickly if left wet or used on acidic foods. It will develop a dark "patina" over time, which many enthusiasts appreciate, but it requires diligent oiling and cleaning.
Superb "Feel": Chefs love Aogami because it provides excellent feedback on sharpening stones and has a distinct "bite" when cutting through protein and vegetables.
The Aogami Grades
There are three primary versions of Blue Steel:
Aogami #2: The most balanced version. It offers a great mix of toughness and edge retention.
Aogami #1: Contains more Carbon and Tungsten than #2. It is harder and stays sharp longer but is more brittle.
Aogami Super (AS): The "king" of the series. It has the highest Carbon content plus added Molybdenum and Vanadium. It offers the best edge retention and is the most wear-resistant, often reaching 64-65 HRC.
Chemical Composition (Aogami #2)
Carbon (C): 1.05% – 1.15% (For high hardness)
Chromium (Cr): 0.20% – 0.50% (Adds some wear resistance and stability)
Tungsten (W): 1.00% – 1.50% (The key ingredient for edge retention)
Manganese (Mn): 0.20% – 0.30%
Common Applications
High-End Japanese Kitchen Knives: Used for Gyutos, Santokus, and traditional single-bevel knives like Yanagiba.
Traditional Folding Knives: Used in the famous Higonokami pocket knives.
Woodworking Chisels: Where a razor-sharp, durable edge is required for precision carving.
Aogami vs. Shirogami (White Steel)
Aogami (Blue): Holds an edge longer and is slightly more forgiving during heat treat, but is a bit harder to sharpen.
Shirogami (White): Can achieve an even finer edge (higher purity) and is easier to sharpen, but loses its edge faster.