Ductile iron pipes are a type of cast iron pipe. Quality requirements dictate that the spheroidizing grade of the cast iron pipes be controlled at levels 1-3 (spheroidizing rate > 80%), thereby significantly improving the material's mechanical properties, combining the essence of iron with the performance of steel. After annealing, the microstructure of the ductile iron pipes consists of ferrite with a small amount of spheroidite, offering excellent mechanical properties, corrosion resistance, ductility, and sealing performance. They are easy to install and mainly used for municipal, industrial, and mining enterprises for water supply, gas transmission, and oil transportation.

A certain number of spherical graphite are distributed on the ferrite and spheroidite matrix. The proportion of ferrite and spheroidite in the matrix varies depending on the nominal diameter and the required elongation. For small diameters, the spheroidite proportion is generally not more than 20%, while for large diameters, it is typically controlled around 25%.