What is the Difference Between Ductile Iron and Cast Iron?

Ductile iron and cast iron are two types of iron alloys with different properties and applications. The main differences between them include:

1. Strength: Ductile iron is typically twice as strong as many grey cast irons and nearly as strong as steel. It is also less brittle than cast iron, making it more durable.
2. Ductility: Ductile iron has a higher ductility than cast iron, meaning it can be bent without breaking. Cast iron, on the other hand, cannot bend without breaking or elongating more than ductile iron without losing its form.
3. Graphite Microstructure: The primary difference between ductile iron and cast iron lies in the way the graphite microstructure is arranged. In grey cast iron, the graphite manifests as flakes distributed throughout the structure. In ductile iron, the graphite is present in the form of nodules, making it more flexible.
4. Casting: Ductile iron is more difficult to cast than cast iron and requires different patterns due to its different shrink rate. It is also slightly more expensive than grey iron but cheaper and easier to cast than steel.
5. Corrosion Resistance: Ductile iron has excellent corrosion resistance, tensile strength, and yield strength, making it suitable for high-demand applications.
6. Weldability: Ductile iron can be welded, while cast iron cannot.

In summary, ductile iron is a more durable and flexible material than cast iron, with better corrosion resistance and weldability. However, it is more difficult to cast and more expensive than cast iron. The choice between the two materials depends on the specific application and requirements of the project.

Comparative Table: Ductile Iron vs Cast Iron

Here is a table comparing the differences between ductile iron and cast iron:

Ductile iron is an alloy of iron rich in graphite, discovered during the mid-1940s. It is more versatile and has higher mechanical properties compared to cast iron, making it suitable for a wide range of applications. On the other hand, cast iron is a brittle material with limited applications due to its lower ductility and impact resistance. The primary difference between the two lies in their microstructures, with ductile iron having graphite in spherical nodules and cast iron having graphite in flake-like or lamellar structures.