Why do ductile iron pipe fittings have sand holes?

Ductile iron pipes are made of magnesium or rare earth magnesium combined with gold spheroidizers added to molten iron before pouring to spheroidize graphite and reduce stress concentration, so that the pipe has the advantages of high strength, high elongation, impact resistance, corrosion resistance, and good sealing. The inner wall is lined with cement mortar, which improves the water supply environment of the pipeline, improves the water supply capacity, and reduces energy consumption. The pipe mouth adopts a flexible interface, and the pipe itself has a large elongation, which makes the pipe more flexible. In the buried pipeline, it can work with the soil around the pipeline to improve the stress state of the pipeline, thereby improving the reliability of the pipeline network operation. Therefore, at present, ductile iron pipes are usually used as main pipes in my country's water supply industry.
Generally, people use paint to apply sand and sand holes in castings. One is that it is hard and difficult to apply paint on the gate. The second is that the pouring temperature is high and the scouring is large during the pouring process. The paint is easy to fall off under scouring and high temperature immersion. Cause sand and sand holes. Many casting factories have not paid much attention to the pouring channel. The scouring of the pouring channel wall during the pouring process is ignored. Therefore, it leads to sand inclusions and sand holes in ductile iron pipe castings. Therefore, in order to improve the casting yield, improve the casting quality and reduce the total casting cost. The casting pouring ceramic pipe is used. This product is easy to use, has the characteristics of smooth circulation, resistance to molten iron and molten steel erosion, no absorption of molten steel, good sawability, etc. It can simplify the molding process, save the difficult work of coating on the inside of the pouring mouth, and improve the layout of the pouring system to avoid sand erosion, sand holes and sand addition defects in the casting. This can be said to be the best way, and everyone can adopt it.
Due to its use environment, corrosion of ductile iron pipe fittings is inevitable. Therefore, we need to understand how to deal with the sand hole phenomenon of ductile iron pipes.