How to identify the quality of ductile iron pipes

Ductile iron pipes are a type of cast iron pipe. In terms of quality, the spheroidization grade of cast iron pipes should be controlled between grades 1 and 3 (spheroidization rate >80%), which allows for better enhancement of the mechanical properties of the cast iron pipes based on the characteristics of iron and the performance of steel. After annealing, the microstructure of ductile iron pipes consists of ferrite with a small amount of pearlite, offering excellent mechanical properties, corrosion resistance, ductility, sealing performance, and ease of installation. They are primarily used in municipal water supply, industrial and mining enterprises for water supply, gas transmission, and oil transportation.

A certain amount of spherical graphite is distributed on the ferritic and pearlitic matrix. Depending on the requirements for nominal diameter and elongation, the ratio of ferrite to pearlite in the matrix varies. For small diameters, the pearlite ratio generally does not exceed 20%, while for large diameters, it is typically controlled around 25%.

Textural phenomena occur due to pits on the surface of ductile iron pipes, which are caused by severe surface wear, leading to unevenness. Scaling phenomena are prone to occur on the lower surface of ductile iron pipes. For some substandard ductile iron pipes in use, cracks may form, primarily due to issues arising from surface cracks during the production process, as well as poor surface quality, which makes the pipes prone to scratches and lacks a good metallic luster. Through these factors, we can assess the quality of ductile iron pipes. When purchasing ductile iron pipes, it is advisable to choose reputable manufacturers to ensure product quality.

For large and medium-sized enterprises, adopting advanced domestic and international testing methods to accurately assess spheroidization status is a reliable guarantee for improving casting quality. However, for small enterprises, especially rapidly emerging township enterprises, utilizing a specific property of ductile iron to indirectly assess spheroidization degree still holds significant practical significance.