Understanding the Difference Between Cast Iron and Steel in CNC Machining(bronze density Kyle)

  • Time:
  • Click:4
  • source:EAGLEBURGER CNC Machining


CNC machining has revolutionized the manufacturing industry, enabling precise and efficient production of various components and products. When it comes to materials for CNC machining, cast iron and steel are commonly used due to their exceptional mechanical properties. In this article, we will explore the differences between these two materials and discuss their applications in CNC machining processes.

1. Cast Iron:
Cast iron is an alloy of iron mixed with carbon and silicon, which gives it its characteristic hardness and brittleness. There are several types of cast iron, including gray cast iron, white cast iron, malleable cast iron, and ductile cast iron, each with unique properties suitable for different applications.

Production Process:
To produce cast iron, the following steps are involved:
1. Melting: A combination of iron, carbon, and other additives such as silicon and manganese is melted in a furnace.
2. Molding: The molten metal is poured into molds made from sand or other refractory materials, allowing it to solidify into the desired shape.
3. Cooling and Finishing: Once cooled, the casting is removed from the mold and undergoes finishing processes like grinding, polishing, or heat treatment to improve its properties.

Properties and Applications:
- High compressive strength and wear resistance make cast iron ideal for components subjected to heavy loads, such as machine bases, engine blocks, and hydraulic cylinders.
- Its excellent damping properties minimize vibrations, making it suitable for applications where stability and precision are essential, such as lathe beds and automotive brake discs.
- However, its brittleness can limit its use in situations requiring impact resistance or flexibility.

2. Steel:
Steel is an alloy primarily composed of iron and carbon (up to 2.1% by weight), along with other elements like chromium, nickel, and manganese. Its unique composition offers high strength, durability, and versatility, making it one of the most widely used materials in CNC machining.

Production Process:
The production process of steel entails the following steps:
1. Ironmaking: Iron ore undergoes a smelting process in a blast furnace, where impurities are removed to obtain pure iron.
2. Steelmaking: The molten iron is then combined with carbon and alloying elements, depending on the desired properties of the steel.
3. Continuous Casting: The liquid steel is solidified through continuous casting, resulting in slabs or billets that can further be processed into various shapes.

Properties and Applications:
- Steel's excellent strength-to-weight ratio makes it suitable for a wide range of applications, including structural components, machine parts, tools, and automotive parts.
- With proper heat treatment, different grades of steel can possess varying levels of hardness, toughness, and corrosion resistance.
- Stainless steel, an alloy containing chromium and nickel, offers enhanced resistance to corrosion, making it ideal for applications in harsh environments or food processing industries.

Differences between Cast Iron and Steel in CNC Machining:

1. Strength and Durability:
Steel generally possesses higher tensile and impact strength than cast iron, allowing it to withstand heavy loads and dynamic forces more effectively.

2. Machinability:
Cast iron tends to have better machinability characteristics due to its graphite microstructure, which acts as a lubricant during the cutting process. However, steel can be machined with appropriate tooling and techniques, allowing for intricate designs and precise tolerances.

3. Heat Treatment:
Steel is more responsive to heat treatments such as case hardening, tempering, and annealing, enabling manufacturers to modify its mechanical properties for specific applications. On the other hand, cast iron exhibits limited response to heat treatment, restricting its versatility.


Understanding the differences between cast iron and steel is crucial in selecting the right material for CNC machining applications. Cast iron offers great strength, stability, and damping properties but is more brittle. Steel, on the other hand, provides excellent strength, machinability, and versatility through various grades and heat treatments. Both materials have their unique applications in different industries, contributing to the advancement of CNC machining technology as a whole.
CNC Milling CNC Machining