Ductile iron pipes are a type of cast iron pipe. The quality requirements for the spheroidizing grade of cast iron pipes are 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 ductile iron pipes consists of ferrite with a small amount of spheroidite, exhibiting good mechanical properties, excellent corrosion resistance, good ductility, superior sealing performance, easy installation, and are 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 ratio of ferrite to spheroidite in the matrix varies depending on the nominal bore size and requirements for elongation. For small bore sizes, the spheroidite ratio is generally not more than 20%, while for large bore sizes, it is typically controlled around 25%.