Features of "Blue paper" steel 

Yasuki Steel is a steel produced at the Yasugi Plant of Hitachi Metals, Ltd. in Yasuki City, Shimane Prefecture, following the tradition of Japanese steel. It has excellent sharpness, toughness, and durability, and this steel is used in many Japanese cutlery. It is divided into blue steel (blue paper), white steel (white paper), yellow steel (yellow paper), etc. according to hardness and composition. 

Blue paper steel is a type of Yasuki steel, and is a high-grade steel with enhanced heat treatment characteristics and wear resistance by adding chromium and tungsten to white steel. Blades made of this steel can be made with high quenching hardness, so it is difficult to sharpen the blade, but once the blade is attached, the sharpness lasts for a long time.