What's the difference between grey cast iron pipe and ductile iron pipe?
Ductile iron pipe is a kind of casting alloy developed in the late 1940s. It is a kind of spheroidal graphite cast iron which is added into the molten iron by adding inoculant and inoculant. The mechanical properties of spherical graphite, so much more better than that of grey cast iron, cast iron, close to the steel, but the price is lower than steel, and still has many excellent properties of ordinary cast iron, such as good casting, shock absorption, machinability and low notch sensitivity etc.. Therefore, many important mechanical parts, such as crankshaft, connecting rod, gear, valve body and cylinder liner, can be made of ductile iron to save steel and reduce cost.
Ductile iron is close to medium carbon steel and is much cheaper. Vermicular graphite iron is the best, but grey iron is worse and white iron is the worst. Therefore, the quality of ductile iron pipe with better quality and price is superior to other cast iron pipe fittings.
Spheroidal graphite cast iron and ordinary cast iron contain graphite monomer, that is to say, cast iron is a mixture of iron and graphite. The graphite in ordinary cast iron is flaky, and the strength of graphite is very low, so there are many flakes of voids in the cast iron, so the strength of ordinary cast iron is lower and more brittle. Graphite in graphite cast iron is spherical, equivalent to the existence of many spherical voids in cast iron. The effect of spherical voids on the strength of cast iron is much smaller than that of sheet voids, so the strength of nodular cast iron is much higher than that of ordinary cast iron.
