What is a grey iron casting?
Molten iron with a controlled carbon and silicon content is poured into a sand mould, and on cooling the carbon forms flakes of graphite. The flakes give excellent machinability, damping and thermal conductivity, and lower cost than steel, but also make the material brittle with lower tensile strength. Grey iron is graded by its minimum tensile strength, and chosen for parts that are mostly loaded in compression.
Listed manufacturers
No grey iron casting manufacturers are listed yet
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List your companyGrey Iron Casting or ductile iron casting?
Grey iron is cheaper, machines easily and damps vibration, but it is brittle and weaker in tension. Ductile iron contains rounded graphite, so it is stronger and can bend before it breaks, which suits parts with shock loads or higher stresses.
What to specify when you ask for a quote
- Grade or specification and the minimum tensile strength you need.
- Hardness range if the part will wear, and the heat treatment if any.
- Casting weight and dimensions, and the tolerance class.
- Who owns and maintains the patterns or tooling.
- Testing required: chemical analysis, tensile and hardness tests, and any pressure or leak testing.
- Machining and surface treatment, in-house or outsourced.
Where it is used
- PumpsPump casings, covers and bases.
- Industrial MachineryMachine beds, housings and frames.
- AutomotiveBrake drums, cylinder blocks and housings.
Frequently asked questions
Why is grey iron used for machine beds?
Its graphite flakes absorb vibration, it is stable and it is easy to cast into complex shapes and to machine. These qualities make it ideal for bases and frames that carry mostly compressive loads.
What does the grade of grey iron mean?
The grade is based on the minimum tensile strength the material must reach. A higher grade is stronger but harder to machine, so choose the lowest grade that meets your load.
How do I specify a grey iron casting?
Provide a drawing, the grade or specification, the weight and quantity, the tests required and any machining. If a pattern is needed, discuss who makes and keeps it.