Malleable Cast Iron is a heat-treated form of cast iron in which brittle cementite is transformed into compact clusters of graphite known as temper carbon. This process significantly improves ductility, toughness, and impact resistance compared to traditional gray iron.
It is commonly used in automotive components, pipe fittings, hardware tools, and industrial machinery where strength, shock resistance, and reliability are required.
Chemical Composition (As-Cast White Iron)
| Element | Typical Range (%) | Role |
|---|---|---|
| Carbon (C) | 2.0 – 2.6 | Forms temper carbon after annealing |
| Silicon (Si) | 0.9 – 1.6 | Aids graphitization |
| Manganese (Mn) | 0.25 – 1.0 | Controls pearlite |
| Sulfur (S) | ≤ 0.20 | Controlled impurity |
| Phosphorus (P) | ≤ 0.20 | Improves fluidity |
| Iron (Fe) | Balance | Matrix |
Key Mechanical Properties
| Property | Typical Range |
|---|---|
| Tensile Strength | 350 – 700 MPa |
| Yield Strength | 250 – 500 MPa |
| Elongation | 5 – 15% |
| Hardness | 120 – 260 HB |
| Impact Strength | Moderate |
| Fatigue Resistance | Good |
Common ASTM Grades:
ASTM A47 / A220 (Ferritic grades – higher ductility, Pearlitic grades – higher strength)
Physical Properties
| Property | Value |
|---|---|
| Density | 7.1 – 7.3 g/cm³ |
| Melting Range | 1,150 – 1,200 °C |
| Thermal Conductivity | 30 – 40 W/m·K |
| Specific Heat | ~460 J/kg·K |
| Thermal Expansion | ~11 µm/m·°C |
| Damping Capacity | Moderate |
Key Characteristics
✔ Improved ductility over gray iron
✔ Good machinability
✔ Better impact resistance than gray iron
✔ Uniform properties in thin sections
Available Forms
Sand-cast components
Thin-section castings
Precision machined parts
Hardware components
Pipe fittings
Applications
Automotive brackets and housings
Pipe fittings and couplings
Clamps, brackets, and hand tools
Agricultural and utility hardware
Electrical conduit fittings
Advantages
✔ Balanced strength and ductility
✔ Good impact resistance
✔ Cost-effective for small to medium parts
✔ Consistent mechanical properties
Limitations
❌ Long heat treatment cycle
❌ Higher cost than gray iron
❌ Lower strength than ductile iron
❌ Size limitations due to annealing
Why Choose Malleable Cast Iron?
Malleable cast iron is ideal when moderate ductility, good machinability, and reliable performance are required in thin-section castings, without the need for full ductile iron strength.