Cast iron is one of the most important ferrous engineering materials.
It is produced by remelting pig iron with scrap iron and coke in a furnace and then casting it into molds.

Cast iron is widely used because it has:

• Good castability

• Good machinability

• High compressive strength

• Low cost

Definition

Cast Iron

Cast iron is an iron–carbon alloy containing about 2% to 4% carbon along with silicon, manganese, sulfur, and phosphorus.

General Composition of Cast Iron

Main Types of Cast Iron

The most commonly used types are:

1. Grey Cast Iron

2. White Cast Iron

3. Malleable Cast Iron

4. Nodular (Ductile) Cast Iron

Unit 14.1: Grey Cast Iron

Grey cast iron is the most commonly used type of cast iron.

It is called grey cast iron because the fracture surface appears grey due to the presence of graphite flakes.

Definition

Grey Cast Iron

Grey cast iron is a type of cast iron in which carbon is present in the form of graphite flakes.

Composition

Typical composition:

Silicon promotes graphite formation.

Microstructure

• Carbon exists as graphite flakes

• Graphite gives the grey appearance on fracture

Properties

Important properties of grey cast iron:

• Good machinability

• High compressive strength

• Good vibration damping capacity

• Good wear resistance

• Low tensile strength

• Brittle in nature

Uses

Grey cast iron is widely used in:

• Machine tool bodies

• Engine blocks

• Pipes and fittings

• Cylinder blocks

• Gear housings

Exam Points

• Graphite present as flakes

• Fracture surface grey

• Best damping capacity