The steel used in Japanese swords is called Wakou or Tamahagane. This is a type of steel made using traditional Japanese methods.

The treated jade steel is very close to modern steel. The average carbon content of jade steel (1.5%) is roughly similar to that of some steel files (1.0~1.2%).

This is because carbon steel with a carbon content of more than 1.3% is very brittle and has no practical value. During the subsequent folding and forging process of jade steel, due to folding and oxidative decarburization, the carbon content will become uniform and further drop to 0.8-1.0%.

The carbon content of the lower left iron (0.7%) is the same as the carbon content of the carbon steel spring wire (0.7%). The carbon content of shop iron is roughly the same as that of construction rebar and angle iron.