BeginnerTopic 22 of 100Materials & Chemical
Cast irons
Grey, ductile and white irons differ by graphite form.
In depth
Cast irons contain 2.1–4% C with Si: grey iron (flake graphite: damping, machinability, low tensile), ductile/nodular (spheroidal graphite: strong and ductile), white iron (cementite: hard, brittle), malleable and compacted graphite. Good castability and low cost.
Key points
- Graphite morphology controls properties
- Cooling rate and inoculation
- Engine blocks and pipes
ExampleDuctile iron pipes carry water mains with strong, ductile behaviour.
Cast irons are used for castings where machinability, damping and low cost matter, and the form of graphite decides their properties.
What is Cast irons?
Grey, ductile and white irons differ by graphite form.
Why is it important to understand cast irons?
Cast irons are used for castings where machinability, damping and low cost matter, and the form of graphite decides their properties.
What makes grey iron different from ductile iron?
Grey iron has flake graphite that gives good damping and machinability but low ductility, while ductile iron has spheroidal graphite for much higher toughness.
Why is white iron hard?
Carbon forms cementite rather than graphite, which makes the surface hard and wear resistant but brittle.
How is Cast irons used in practice?
Typical applications include casting an engine block from grey iron for its damping, choosing ductile iron for a pressure housing that must flex and selecting white iron for a wear-resistant liner.
What should I learn before Cast irons?
Study "Hardenability" first (topic 21 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Cast irons?
Graphite morphology controls properties. Cooling rate and inoculation. Engine blocks and pipes.
Can you give an example of Cast irons?
Ductile iron pipes carry water mains with strong, ductile behaviour.
What comes after Cast irons?
The next topic is "Stainless steels", which builds directly on this one.
How difficult is Cast irons?
It is classed as Beginner in Materials & Chemical (topic 22 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.