Cast Iron and Ductile Iron

Some buyers may wonder the relations of cast iron and ductile iron. So, what is cast iron? Cast iron should be a kind of metal, or specific iron casting part. Iron foundry melts the pig iron into hot liquid iron, and pour it into various heat-resistant molds, then get cast iron parts, or called iron castings. Therefore, cast iron is usually referred to iron casting, which means the metal casting is made by iron, not by steel or aluminum. There are many types of cast iron, mainly divided into gray iron, ductile iron and malleable iron. 

The main difference between ductile iron, gray iron and malleable iron is the morphology of the graphite particles which take on a nodular, flaky or cottony form or after suitable treatments are made to the melt. The different microstructures of graphite cause the different physical properties.

Ductile iron is also known as nodular iron or spheroidal graphite iron, which is a type of cast iron invented in 1943 by Keith Millis. While most varieties of cast iron are brittle, ductile iron and malleable iron are much more flexible and elastic, due to its nodular and cottony graphite inclusions. The malleable iron has been replaced by ductile iron in the recent years. It is mainly because the improved physical properties of ductile iron, and its reduced production costs than before.

The ductile iron has many good physical properties:

1. Good hardness and good wear resistance

2. Better corrosion resistance

3. Have high tensile and yields strengths that vary widely across the various grades

4. Impact strengths are better than gray irons, with lower grades approaching values common for mild steel

5. Fatigue strengths are better

Since you have understood the relations between cast iron and ductile iron, you may wonder how you should choose the suitable cast iron for making your parts. You should consider the tensile strength. The tensile strength is a very important physical properties for cast iron. If your parts need to work in a hostile environment, or called as sturdy, then you should consider to use ductile iron because its high tensile strength and good elongation. Otherwise, the gray iron should be a good choice because its lower costs.

You could find many iron foundries in China, who could produce various iron castings, but mainly gray iron and ductile iron.

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