The Difference Between Cast Iron and Steel in CNC Machining(32 finish Walker)

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CNC machining is a versatile manufacturing process that involves the use of computer-controlled machines to produce complex parts from various materials. Two commonly used materials in CNC machining are cast iron and steel. While both have their own merits, knowing the differences between these materials can help optimize their usage in different applications. This article aims to shed light on the dissimilarities between cast iron and steel and how they impact CNC machining processes.

1. Composition and Properties:

Cast Iron:
Cast iron is an alloy primarily composed of iron with varying amounts of carbon and silicon. It is known for its high carbon content, typically ranging from 2% to 4%. This high carbon content gives cast iron its unique properties such as excellent wear resistance, good machinability, high compression strength, and superior damping capability. However, it also makes cast iron brittle and susceptible to cracking under excessive load or stress.

Steel, on the other hand, is an alloy made primarily from iron along with controlled quantities of carbon. Unlike cast iron, steel has a lower carbon content, typically less than 2%, which imparts greater flexibility and toughness. Depending on the intended application, steel can be further modified by adding elements like chromium, nickel, or molybdenum to enhance specific properties such as corrosion resistance, hardness, or heat resistance.

2. Machinability:

The difference in composition affects the machinability of cast iron and steel during CNC machining.

Cast Iron:
Due to its low melting point and self-lubricating properties, cast iron is considered easy to machine. Its graphite flakes act as a built-in lubricant, reducing friction between the cutting tool and the workpiece. This feature allows for higher cutting speeds and feeds, resulting in shorter machining times. However, the brittleness of cast iron demands careful handling during machining operations to prevent cracking or structural damage.

Although steel is generally harder than cast iron, it can be machined with the right cutting tools and techniques. The lower carbon content makes steel less prone to chipping or breaking during machining operations. Various types of tool coatings, coolant systems, and cutting speeds need to be considered when working with different grades of steel to optimize productivity and surface finish.

3. Applications:

Cast Iron:
The unique properties of cast iron make it well-suited for applications that require high strength, stiffness, and resistance to wear or vibration. It is commonly used in the manufacturing of automotive parts, engine blocks, pipes, machinery bases, and heavy-duty equipment components.


Steel's versatility and durability allow it to be utilized in a wide range of CNC machining applications. From aerospace components and precision tools to household appliances and architectural structures, steel's strength, corrosion resistance, and formability make it an ideal choice for various industries.

In summary, the differences between cast iron and steel in CNC machining lie primarily in their composition, properties, machinability, and applications. Cast iron offers excellent wear resistance and damping properties but is more brittle compared to steel. Steel, with its lower carbon content, provides greater flexibility and toughness. Understanding these differences enables engineers to select the appropriate material for specific applications, ensuring efficient and reliable CNC machining processes. CNC Milling