The essence of cast iron pipe fitting is ductile iron pipe fitting, because ductile iron pipe fitting has the nature of iron, steel performance, so there is this term. Graphite exists in spherical shape in nodular cast iron pipes. Generally, the size of graphite is 6-7 grade. In quality, the nodularization grade of cast iron pipes is required to be controlled at 1-3 grade and the nodularization rate is more than 80%. Therefore, the mechanical properties of the material itself have been improved, which has the nature of iron and the properties of steel. After annealing, the nodular cast iron pipe has ferrite and pearlite in its metallographic structure. It has good mechanical properties, so it is also called cast iron pipe.