Cast iron vs Steel
Cast iron and Steel are genuine alternatives to one another — a choice somebody actually makes — and differ on 3 measured properties, density most clearly.
Cast iron vs Steel
Cast iron
Iron with enough carbon to pour but not to forge — brittle, cheap, superb at damping vibration, and the material the industrial revolution was built from.
Steel
Iron with a controlled, small proportion of carbon — the most-used engineered material in the world.
| Property | Cast iron | Steel |
|---|---|---|
| Density | 6.8–7.8 g/cm³ | 7.75–8.05 g/cm³ higher |
| Electrical conductivity Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 6.99 MS/m |
| Melting point | 1150–1200 °C | 1370–1510 °C higher |
| Tensile strength | 150–400 MPa | 400–2000 MPa higher |
| Thermal conductivity Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 15–54 W/(m·K) |
Choosing between them
Cast iron is recorded as a substitute for Steel — cheaper, easier to work.
What it gives up: Brittle. It is unusable where a member is loaded in tension, which is what its nineteenth-century failures taught.
Partial substitute, on the evidence cited above.