Ductile iron pipe manufacturing

Chilled iron pipes with a diameter of No. 18 or larger, after being treated with nodularizing agents, are cast into pipes through high-speed centrifugal casting in a centrifugal ductile iron casting machine. These pipes are referred to as "Ductile Cast Iron Pipes," commonly abbreviated as ductile iron pipes, nodular iron pipes, or spheroidal graphite cast iron pipes. They are primarily used for water supply transmission and are an ideal material choice for water pipelines.

In many regions across our country, the connection between medium and small diameter pipe sections for water supply utilizes socket-and-spigot or flanged joints for ductile iron pipes; ductile iron allows for limited bending angles and requires superior seismic resistance and sealing properties.

The main components of ductile iron pipes include carbon, silicon, manganese, sulfur, phosphorus, and magnesium, among others.

Standard of Execution: International Standard ISO 2531:1998 and National Standard GB 13295-2008

Ductile Cast Iron Pipes, abbreviated as DIPs, are pipes manufactured by casting molten iron, numbered 18 or higher, with an addition of nodulizing agent, through a centrifugal process in a ductile iron centrifugal casting machine.

Ductile iron pipes are a type of cast iron pipe. The quality requirements call for the spheroidizing grade of the cast iron pipe to be controlled at 1-3 levels (spheroidizing rate > 80%), thereby significantly improving the mechanical properties of the material itself, which boasts the essence of iron and the performance of steel. After annealing, the microstructure of the ductile iron pipes consists of ferrite plus a small amount of spheroidite, featuring excellent mechanical properties, corrosion resistance, ductility, sealing performance, and ease of installation. They are primarily used for municipal and industrial water supply, gas transmission, and oil transportation.

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

Mechanical properties

Minimum tensile strength: 420 MPa, minimum yield strength: 300 MPa, minimum elongation: 7%

Bore Size: DN80 - DN1600

Performance

Ductile iron pipes are a type of cast iron, an alloy of iron, carbon, and silicon. In ductile iron, graphite exists in spherical form, usually ranging from 6 to 7 grades in size. Quality requirements call for the spheroidizing grade of the pipes to be controlled at 1 to 3 levels (spheroidizing rate ≥ 80%), thus significantly improving the material's mechanical properties. They retain the essence of iron while offering the performance of steel. After annealing, ductile iron pipes have a microstructure of ferrite plus a small amount of pearlite, exhibiting good mechanical properties.

Ductile iron pipes, commonly known as centrifugal ductile iron pipes, possess the essence of iron and the properties of steel. They offer excellent corrosion resistance, good ductility, superior sealing, easy installation, and are primarily used for municipal and industrial water supply, gas, and oil transportation. They are the preferred choice for water supply pipes due to their high cost-performance ratio. Compared to PE pipes, ductile iron pipes are simpler and quicker to install, with better internal and external pressure after installation. In terms of tightness and corrosion resistance, the sealed performance of ductile iron pipes is superior, and their corrosion resistance can be enhanced through various protective measures. From a hydraulic performance perspective, due to the fact that the specifications of ductile iron pipes generally refer to the inner diameter while PE pipes refer to the outer diameter, ductile iron pipes can achieve greater flow rates under the same specifications. In terms of overall installation and maintenance costs, ductile iron pipes offer a more favorable cost-performance ratio. Internal zinc spraying and cement sand mortar for corrosion protection are also common.