1. Blast furnace boiling water.
2. Hot iron electric furnace quenching and tempering. Refine low-phosphorus and low-sulfur molten iron and ensure that the content of carbon, phosphorus and sulfur in the molten iron meets the requirements. During the quenching and tempering process, the intermediate frequency electric furnace guarantees the stability of the composition of the molten iron through advanced analysis and perfect process control.
3. Spheroidization of molten iron. The molten iron produced by the electric furnace is added with spheroidizing agent for spheroidizing treatment, and the composition is adjusted to meet the process requirements. Each furnace of molten iron must be analyzed by a spectrometer to make the molten iron fully meet the requirements of centrifugal casting.
4. Core making.
5. Centrifugal casting. Centrifugal casting is carried out using water metal technology. The molten iron at about 1360°C melted in the electric furnace is continuously poured into a high-speed rotating tube mold, and the molten iron is solidified by water cooling to form a ductile iron pipe.
6. Weigh.
7. Annealing. It means to slowly heat the ductile iron pipe to a certain temperature, keep it for enough time, and then cool it at an appropriate speed. The purpose is to reduce the hardness, improve the machinability; eliminate residual stress, stabilize the size, reduce deformation and crack tendency; refine the crystal grain, adjust the structure, and eliminate the structure defect.
8. Spray zinc. In order to further enhance the corrosion resistance of the ductile iron pipe, it is necessary to spray zinc on the outer surface of the pipe. It is sprayed with metallic zinc, and the material is metallic zinc with a zinc content of more than 99%. In order to ensure the quality of zinc spraying, zinc spraying should be carried out after the heat treatment process is completed and the pipe itself is still at a certain temperature.
9. Rounding and polishing.
10. Water pressure test. In accordance with the international ISO standards, each ductile iron pipe is subjected to a hydraulic test. Once leakage occurs, the pipe is immediately scrapped. All cast iron pipes are not repaired by welding or glue.
11. Cement internal coating.
12. Keep in good health. Create proper temperature and humidity to increase the strength of cement.
13. Asphalt spraying: After heating the zinc-sprayed ductile iron pipe after internal coating and curing, the imported asphalt paint is sprayed by the asphalt external coating machine under high pressure to increase the anti-corrosion ability of the ductile iron pipe.
14. Finished ductile iron pipe.
