News - Ductile Iron Pipe Production Process: Rigorous Process to Cast High-quality Pipes

In modern industrial manufacturing, ductile iron pipes are widely used in water supply, drainage, gas transmission and other fields due to their excellent mechanical properties and corrosion resistance. In order to ensure the high quality and high reliability of ductile iron pipes, their production process must be strictly controlled and finely processed. From the preparation and spheroidization of molten iron, to centrifugal casting, annealing, and finishing processes such as zinc spraying, grinding, hydraulic pressure testing, cement lining and asphalt spraying, every link is crucial. This article will introduce the production process of Ductile Cast Iron Pipe in detail, and show how to ensure that each pipe can meet international standards and actual use requirements through scientific management and advanced technical means, and provide reliable infrastructure guarantees for various engineering projects.

1. Preparation of Molten Iron
Molten Iron Preparation and Spheroidization: Select high-quality casting pig iron as raw material, such as high-quality ductile casting pig iron, which has the characteristics of low P, low S, and low Ti. According to the specifications of the pipe diameter to be produced, the corresponding raw materials are added to the medium frequency electric furnace, which modulates the molten iron and heats it to the temperature required by the process, and then adds the spheroidizing agent for spheroidization.
Hot Iron Quality Control: In the process of molten iron preparation, the quality and temperature of each link are strictly controlled. Each furnace and each bag of molten iron must be analyzed by the direct reading spectrometer to ensure that the molten iron fully meets the casting requirements.

2. Centrifugal Casting
Water-cooled Metal Mold Centrifuge Casting: Water-cooled metal mold centrifuge is used for casting. High-temperature molten iron is continuously poured into the high-speed rotating pipe mold. Under the action of centrifugal force, the molten iron is evenly distributed on the inner wall of the pipe mold, and the molten iron is quickly solidified by water cooling to form a ductile iron pipe. After the casting is completed, the cast pipe is immediately inspected and weighed for casting defects to ensure the quality of each pipe.
Annealing Treatment: The cast Iron Tube is then placed in the annealing furnace for annealing treatment to eliminate the internal stress generated during the casting process and improve the metallographic structure and mechanical properties of the pipe.
Performance Testing: After annealing, the ductile iron pipe is subject to a series of strict performance tests, including indentation test, appearance test, flattening test, tensile test, hardness test, metallographic test, etc. Pipes that do not meet the requirements will be scrapped and shall not enter the next process.

3. Finishing
Zinc Spraying: The ductile iron pipe is treated with zinc by using a high-voltage electric spray machine. The zinc layer can form a protective film on the surface of the pipe to enhance the corrosion resistance of the pipe.
Grinding: Qualified Ductile Iron Drainage Pipe are sent to the third grinding station for appearance inspection, and the socket, spigot and inner wall of each pipe are polished and cleaned to ensure the flatness and finish of the pipe surface and the sealing of the interface.
Hydrostatic Test: The corrected pipes are subjected to hydrostatic test, and the test pressure is 10kg/cm² higher than the ISO2531 international standard and European standard, so as to ensure that the pipes can withstand sufficient internal pressure and meet the pressure requirements in actual use.
Cement Lining: The inner wall of the pipe is centrifugally coated with cement by a double-station cement lining machine. The cement mortar used has undergone strict quality inspection and ratio control. The entire coating process is controlled by a computer to ensure the quality uniformity and stability of the cement lining. The pipes lined with cement are cured as required to fully solidify the cement lining.
Asphalt Spraying: The cured pipes are first heated on the surface, and then asphalt is sprayed by a double-station automatic sprayer. The asphalt coating further increases the anti-corrosion ability of the pipes and extends the service life of the pipes.
Final Inspection, Packaging and Storage: The pipes sprayed with asphalt are subjected to final inspection. Only fully qualified pipes can be sprayed with marks, and then packaged and stored as required, waiting to be sent to various places for use.