How many kinds of steelmaking techniques were there during the Spring and Autumn Period and the Warring States Period?

There are two kinds of steelmaking techniques in the Spring and Autumn Period and the Warring States Period: one is to put the iron block directly in hot carbon for a long time, heat it to carburize the surface, and then forge it repeatedly to make it carburized steel. The other is to mix block ironmaking with carburizing agent and catalyst, seal and heat, and carburize into steel, commonly known as "braised steel". This is a long-standing steelmaking method in China.

In addition, the long-standing "stewing steel" smelting method in Henan, Hubei, Jiangsu and other places is to put the cooked iron block into a ceramic or iron container, add carburizing agent according to a certain formula, use phosphorus-containing bone powder as the main catalyst, and then seal and heat it to carburize it into steel.

Stewed steel smelting method