Ductile iron production process

The production process of ductile iron mainly includes the following steps:

1.Tempering of hot metal in electric furnace: Refining low-phosphorus and low-sulfur hot metal, and ensuring that the content of carbon, phosphorus and sulfur in the hot metal meets the requirements.

2.Tempering of medium-frequency electric furnace: During the tempering process, advanced analysis and perfect process control are used to ensure the stability of the hot metal composition.

3.Hot metal spheroidization: Hot metal produced by electric furnace is spheroidized with spheroidizing agent to adjust the composition to meet the process requirements. Each furnace of hot metal must be analyzed by spectrometer to make the hot metal fully meet the requirements of centrifugal casting.

4.Core making: Make sand cores or other types of cores according to product requirements.

5.Centrifugal casting: Centrifugal casting is carried out using water metal process. The hot metal at about 1360℃ after melting in the electric furnace is continuously poured into the high-speed rotating pipe mold, and the hot metal is solidified by water cooling to form a ductile iron pipe.

6.Weighing: Weigh the cast pipe to ensure that the quality and specifications of the product meet the requirements.

7.Annealing: Slowly heat the ductile iron pipe to a certain temperature, keep it for a sufficient time, and then cool it at an appropriate speed. The purpose is to reduce hardness and improve machinability; eliminate residual stress, stabilize size, reduce deformation and crack tendency; refine grains, adjust structure, and eliminate structural defects.

8.Zinc spraying: In order to further enhance the corrosion resistance of ductile iron pipes, zinc spraying is required on the outer surface of the pipe. Metal zinc spraying is used, and the material is metal zinc with a zinc content of more than 99%. To ensure the quality of zinc spraying, zinc spraying should be carried out after the heat treatment process is completed and the pipe body itself is still at a certain temperature.

9.Rounding and grinding: Rounding and grinding the cast pipe to improve surface quality and dimensional accuracy.

10.Hydrostatic test: Hydrostatic test is carried out on each ductile iron pipe in accordance with international ISO standards. Once leakage occurs, the cast pipe will be scrapped immediately. All cast iron pipes are not welded or glued.

11.Cement internal coating: Cement internal coating is applied on the inner surface of the pipe to improve the corrosion resistance and service life of the pipe.

12.Cure: Create appropriate temperature and humidity to continuously increase the strength of cement.

13.Asphalt spraying: After the zinc-sprayed ductile iron pipe after internal coating and curing is heated, the asphalt external coating machine sprays imported asphalt paint under high pressure to increase the corrosion resistance of the ductile iron pipe.

14.Ductile iron pipe finished product: After the above process steps, the ductile iron pipe finished product is produced.