Bainite is a structure of high-carbon steel that combines great strength with excellent flexibility and shock absorption characteristics. It has been known as an exemplary Katana blade component for a number of years but its use has been restricted to a few top-class master smiths, due to the difficulties involved in performing the exacting heat treatment procedures necessary for the production of a Bainite blade body in combination with the very hard Martensite Yakiba (edge section) required for Katana blades.

Hanwei has now mastered this difficult process, using billets of L-6 tool steel (a very tough high-carbon low-alloy steel) as a starting point. Blades are forged and shaped in the normal way, then carefully heat treated to achieve the required Bainite and Martensite structures before final polishing.