Ductile iron can be bent without breaking, whereas cast iron is brittle and breaks when bent.

As ductile iron can be bent, it can be made into different shapes and forms. But one cannot make out different shapes and forms using cast iron. While ductile iron is flexible, cast iron is not.

When comparing the two, cast iron corrodes more quickly than ductile iron.

Ductile iron consists of iron, carbon, silicon, manganese, magnesium, phosphorous and sulphur. Tin and copper are also sometimes found. Ductile iron also consists of nodular graphite, which gives it flexibility. Cast iron mainly consists of carbon and silicon.
With regard to practical uses, ductile iron pipes are used in sewer and water lines. This is because they are much stronger than cast iron. Moreover, ductile iron is better than cast iron in difficult terrains.
Ductile iron is mainly used in the automobile industry such as trucks, tractors and oil pumps. Cast iron is mainly seen in the construction industry.
It was Keith Millis who discovered ductile iron in 1943. Cast iron has been in use for many centuries. China is credited with the invention of cast iron in the 4th century BC. It was used first for making weapons, pots, ploughshares and pagodas. The western people knew cast iron only in the late 14th century.

Summary

1. Ductile iron can be bent without breaking.
2. Cast iron is brittle and it breaks when bent.
3. While ductile iron is flexible, cast iron is not.
4. As ductile iron can be bent, it can be made into different shapes and forms. One cannot make out different shapes and forms using cast iron.
5. Cast iron corrodes more quickly than ductile iron.
6. Ductile iron is mainly used in the automobile industry such as trucks, tractors and oil pumps. Cast iron is mainly seen in the construction industry.
7. Ductile iron consists of nodular graphite that give it flexibility.
8. It was Keith Millis who discovered ductile iron in 1943. China is credited with the invention of cast iron in the 4th century BC.

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