Blue #2, Aogami 2 or Blue Paper Steel are names for a traditional knife steel of Japanese kitchen knives. There are different steels used for forging Japanese knives, Aogami 2 is very commonly used for traditional types of knives, such as the Bunka knife or the Santoku knife.

White #2 (Shirogami 2) and Blue #2 (Aogami 2) differ in composition. Aogami 2 contains additional chromium and tungsten and can be tougher and more robust than Shirogami 2 knife steel depending on processing techniques.

Aogami 2 (jap. 青紙) knife steel can reach a hardness level of 62 - 65 HRC (Rockwell). However, in addition to the selection of the steel, the forging technique and the experience of the Japanese knifemakers are also largely responsible for the degree of hardness. Blue #2 can be easily resharpened, the best way to do this is to use water sharpening stones.