Difference among ductile iron, gray iron and malleable iron

Ductile Iron:

• Graphite Structure: Spherical graphite nodules.  
• Properties: High strength, excellent ductility, good impact resistance, and good wear resistance.  
• Production: Produced by adding magnesium or cerium to molten iron, which causes the graphite to form into spheres.
• Applications: Widely used in automotive components (crankshafts, cylinder blocks), pipes and fittings, valves, and machinery parts.  

Gray Iron:

• Graphite Structure: Flake-shaped graphite.  
• Properties: Good machinability, good wear resistance, and good damping capacity. However, it has low ductility and impact resistance.  
• Production: The most common type of cast iron, produced by cooling molten iron slowly.
• Applications: Widely used in machine beds, engine blocks, brake drums, and other applications where good wear resistance and damping are crucial.

Malleable Iron:

• Graphite Structure: Irregularly shaped graphite flakes.
• Properties: Good ductility, moderate strength, and good impact resistance.  
• Production: Produced by annealing white cast iron, which transforms the graphite structure.  
• Applications: Used in automotive components (suspension parts, steering knuckles), agricultural equipment, and hardware.  

Here’s a table summarizing the key differences:

In essence:

• Ductile iron excels in strength, ductility, and impact resistance, making it suitable for demanding applications.  
• Gray iron is preferred for its machinability and wear resistance.
• Malleable iron offers a good balance of ductility, strength, and impact resistance.

The choice of iron type depends on the specific requirements of the application.