Production Process of Ductile Iron Pipe

1. Melting and tempering

Add raw materials (scrap steel, molten iron, return charge, etc.) into the induction furnace and adjust its composition. When the composition meets the process requirements, add the quenched and tempered molten iron into the spheroidizing agent for spheroidizing treatment to meet the process requirements.

2. Heat treatment

Ductile iron pipes produced by centrifugal casting have a large amount of cementite in the metallographic structure, so the mechanical properties of ductile iron pipes can not meet the requirements of ISO2531 standard. For this reason, it is necessary to anneal the ductile iron pipe and change its basic structure into ferrite-based ductile iron pipe fittings with cementite to make its performance meet the requirements of ISO2531 standard.

3. Centrifugal casting

Install the bell core on the centrifuge, pour the spheroidized qualified molten iron into the quantitative package, set the amount of inoculant added, the amount of pipe mold powder added, the rotation speed of the centrifuge, the walking speed and the turnover speed of the quantitative package according to the requirements of the process regulations. The molten iron is poured into the rotating pipe mold with the turnover of the quantitative package and the walking of the centrifuge, and solidified into a pipe. The pipe is pulled out of the mold by the pipe puller and sent to the heat treatment department.

4. Spheroidization

When the composition and temperature of the molten iron meet the process requirements, the spheroidizing agent is added to the molten iron to make the flake graphite in the molten iron become spherical graphite, and sent to the centrifugal casting department for pouring.

5. Zinc spraying

In order to further enhance the performance of ductile iron pipes, zinc spraying treatment should be carried out on the outer surface of ductile iron pipes. In order to improve the quality of zinc spraying, the best effect is to spray zinc when the pipe body is still at temperature after the completion of the heat treatment process.

6. Cement lining

In order to ensure the water delivery sanitation of ductile iron pipes, prevent the scaling on the inner wall of ductile iron pipes, increase the water delivery resistance, and reduce the service life of the pipe network, the water delivery pipes should be lined with cement. Mortar lining shall comply with ISO2531 and ISO4179 standards.

7. Rounding and polishing

In order to ensure the surface quality of ductile iron pipe and the installation size of socket, the socket and inner wall of ductile iron pipe need to be polished and cleaned.

8. Hydrostatic test

In order to ensure the ex-factory quality of ductile iron pipes and the installation performance of the pipe network during use, the ductile iron pipes shall be subject to hydraulic test and inspection according to the standards specified in ISO2531.

9. External coating and packaging

To prevent the ductile iron pipe from being corroded underground and prolong the service life of the pipe network, the outer surface of the ductile iron pipe should be coated with a layer of asphalt paint, and then packaged and put into storage.