What is Ductile Iron?
Ductile iron is a type of iron casting technology and is generally known as nodular cast iron, which has different properties than gray iron. Ductile iron is a type of cast iron in which carbon is dispersed in the form of graphite nodules. This structure makes ductile iron more ductile and durable than gray iron.

Properties of Ductile Iron
The distinctive properties of ductile iron distinguish it from gray iron and make it more preferred in certain applications:

  • High Ductility and Durability: Unlike gray iron, ductile iron has high ductility and durability. This feature makes the material more resistant to impact and stress.
  • Low Brittleness: Ductile iron is less brittle than gray iron. This provides a great advantage, especially in applications where mechanical loads are high.
  • Good Machinability: Ductile iron is similar to gray iron in terms of machinability and can be easily shaped.
  • High Tensile Strength: The tensile strength of ductile iron is higher than that of gray iron. This makes the material more resistant to tensile forces.

Usage Areas of Ductile Iron
Ductile iron is widely used in many industrial areas due to its properties. Here are some common areas of use of ductile iron:

  • Automotive Industry: Ductile iron is preferred in automotive components such as crankshafts, axles, suspension parts and brake systems.
  • Machine Manufacturing: Ductile iron is used in heavy machinery parts, pump bodies and compressor parts.
  • Pipes and Fittings: High-pressure-resistant pipes and fittings are made of ductile iron.
  • Construction and Infrastructure: Ductile iron is preferred in sewer covers, gratings and pipelines.

Ductile Iron Production Process
Ductile iron production consists of certain steps, and these steps are similar to gray iron production, but there are some differences:

  1. Melting: Iron is melted in blast furnaces and alloying elements such as carbon and silicon are added.
  2. Modification: Magnesium is added to the molten metal. This allows the carbon to separate into graphite nodules.
  3. Casting: The modified metal is poured into pre-prepared molds.
  4. Cooling and Solidification: The poured metal cools and solidifies in the molds. During this process, graphite forms in a nodular structure.
  5. Machining: Solidified ductile iron parts are processed to the desired precision and shapes.
  6. Finishing: Casting parts are subjected to processes such as heat treatment, surface cleaning and coating in order to increase surface quality and meet the requirements.

Comparison of Ductile Iron and Cast Iron
Cast iron and spheroidal cast iron are two types of castings with different properties, and both offer different advantages:

  • Cast Iron: Known for its high carbon content and easy machinability. It has high corrosion resistance, but has the disadvantages of brittleness and low tensile strength.
  • Ductile Iron: Stands out with its high ductility, durability and tensile strength. It offers low brittleness and good machinability, but its production costs can be higher than cast iron.

History of Ductile Iron: The Birth of a Miraculous Material

Ductile iron was developed in 1943 by Swiss metallurgist Dr. Robert A. Staufer and is a groundbreaking method in foundry. Let’s explore the story of this miraculous material:

Dr. Staufer was trying to develop a new alloy to eliminate the disadvantages of cast iron. Aiming to solve problems such as the brittleness and low extension strength of gray iron, Staufer focused on changing the graphite structure.

Staufer added elements such as magnesium and cerium to gray iron, allowing the graphite to transform into a spherical structure. These spherical graphites gave the material greater toughness and flexibility, significantly reducing brittleness.

The Birth of Ductile Iron
This revolutionary invention was called “ductile iron” and was commercially launched in 1948. Ductile iron quickly gained popularity as a more durable, flexible and workable alternative to gray iron.

Impact on the Industry
The development of ductile iron led to significant changes in many industries. Ductile iron began to replace gray iron in areas such as automotive, machine manufacturing, agricultural machinery and railway equipment.

Advantages of Ductile Iron

  • Higher strength and yield strength compared to cast iron
  • More toughness and flexibility
  • Better workability
  • Less casting defects
  • Longer-lasting products

Ductile Iron Today
Ductile iron is one of the most widely used alloys in foundry today. Although it is more expensive than cast iron, the superior features it provides make it preferred in many sectors.

Dr. Staufer’s invention, spheroidal iron, is a turning point in the history of foundry. Eliminating the disadvantages of cast iron and bringing innovation to many sectors, spheroidal iron maintains its importance today and is expected to continue to play an important role in the future.

Mechanical and Physical Properties of Ductile Iron
Ductile iron is a casting method consisting of iron and carbon alloy in which graphite is present in spherical shapes. Ductile iron, which has many advantages compared to cast iron and gray iron, stands out with its mechanical and physical properties.

Mechanical Properties

  • Strength: Ductile iron has high strength compared to gray cast iron and gray cast iron. This makes it a more durable and long-lasting material.
  • Toughness: Ductile iron has high toughness. This makes it more resistant to impacts and vibration.
  • Hardness: Ductile iron has a hardness between 200-300 HB on the Brinell hardness scale. This hardness provides resistance to wear and facilitates cutting and chip removal.
  • Extension Strength: Ductile iron has high extension strength compared to gray cast iron and gray cast iron. This makes it more resistant to tension and pull.
  • Fatigue Strength: Ductile iron has high fatigue strength compared to gray cast iron and gray cast iron. This makes it an ideal material for parts subjected to repeated loads.
  • Modulus of Elasticity: The modulus of elasticity of ductile iron is between 150-200 GPa. This value indicates the flexibility of the material and its resistance to deformation.

Physical Properties

  • Density: The average density of ductile iron is 7.5 g/cm³. This value is quite high compared to other types of cast iron and other metal alloys such as steel.
  • Melting Point: The melting point of ductile iron is between 1250-1350°C.
  • Heat Conductivity: The heat conductivity of ductile iron is between 45-60 W/(m K). This value indicates the ability of the material to conduct heat and makes ductile iron suitable for heating and cooling applications.
  • Coefficient of Thermal Expansion: The coefficient of thermal expansion of ductile iron is 10-11 x 10⁻⁶ m/m K. This value indicates the rate at which the material expands with heat.
  • Magnetic Properties: Ductile iron is a magnetic material. This makes it suitable for parts used in magnetic fields, such as electric motors and generators.

Other Important Properties

  • Castability: Ductile iron has excellent castability. This allows parts with complex shapes to be easily cast.
  • Machinability: Ductile iron can be machined more easily than gray cast iron and gray cast iron. Operations such as drilling, milling, grinding and welding can be applied.
  • Recyclability: Ductile iron is a 100% recyclable material. This makes it an environmentally friendly option.