During the Spring and Autumn Period, China first invented pig iron casting technology in the world, and smelting pig iron must have several basic conditions: one is to have a high enough temperature, the second is to always maintain a strong enough reducing atmosphere, and the third is to have a large enough smelting space. Ancient China invented the shaft furnace copper smelting very early, accumulated a whole set of high temperature reduction smelting experience, the Central Plains in the smelting block iron soon after smelting, smelting pig iron. Changsha Yangjiashan tripod is the earliest pig iron castings found so far in China and the world.
In 1977, a Warring States cast-iron site was discovered outside the city of Yang, Dengfeng, Henan Province, and many remnants of the furnace bottom and wall were unearthed. The former is made of clay mixed with coarse sand, and the latter according to the different working positions, there are three situations from the material to the construction method: one is the residual block around the bottom of the furnace, which is made of refractory mud inserted into the iron hoe residual block; the other is the residual block of the inner wall of the furnace, which is built with mud strips; the third is the residual block of the furnace wall mouth, which is made of grass mixed mud strips overlapping.
