Named for blue paper put on steel at Hitachi factory. Aogami (blue) steels are graded as Super, #1 and #2.. All made from same iron stock as Shirogami (white) steel, Aogami steels have high carbon (1.1-1.5%), .5% chromium for carbide formation and tungsten for edge life. Aogami Super has added vanadium for wear resistance.
Typically Aogami Super has the longest edge life, #1 has the best edge formation and #2 the best toughness. Aogami steels do not sharpen as easily as Shirogami, but they cut better as they dull.
Highly recommended for professionals that need good edge life. Aogami steels have little corrosion resistance and special attention is required to prevent rusting.