Aogami (Blue Steel)

Aogami (青紙, “blue paper,” named after the paper the maker Hitachi wraps it in) is white steel with tungsten and chromium added. Those elements improve wear resistance, so the edge lasts longer, and they widen the temperature window for hardening, which makes the steel more forgiving for a smith to work. It is still a carbon steel: it takes a very fine edge, and it will develop a patina and spot-rust if you do not dry it. Aogami Super pushes the alloy content and hardness further again. Most cooks find Blue steel a slightly more practical choice than White for a carbon knife they actually use.