What's the Difference Between Cast Steel and Cast Iron

In metalworking and manufacturing, cast steel and cast iron are two common casting materials, each with unique physical properties and applications. Knowing the difference between the two is essential for engineers, manufacturers, and material science enthusiasts. This article will take a deep look at the essential differences between cast steel and cast iron, and their applications in different fields.

 

Differences in Chemical Composition

 

The essential difference between cast steel and cast iron lies in their chemical composition. In the engineering field, iron alloys with a carbon content of more than 2% are generally considered to be cast iron, while those with a carbon content of less than this value are classified as steel. Specifically, industrial cast iron usually contains 2% to 4% carbon, which is mostly present in the form of graphite and sometimes in the form of cementite. In addition, cast iron also contains 1% to 3% silicon, as well as elements such as manganese, phosphorus, and sulfur. Alloy cast iron may also contain other alloying elements such as nickel, chromium, molybdenum, aluminum, and copper.

 

In contrast, although cast steel also contains a certain amount of carbon, its content is much lower than that of cast iron, usually between 0.1% and 2%. Other alloying elements such as chromium, nickel, molybdenum, etc. may also be added to cast steel to improve its mechanical properties and corrosion resistance.

 

Physical properties and applications

 

Due to the different chemical compositions, cast steel and cast iron show significant differences in physical properties. Cast steel usually has better plasticity and toughness, which is manifested in higher elongation, cross-sectional shrinkage and impact toughness. This makes cast steel perform well in parts that need to withstand large impact forces and complex stress states, such as bridge structures, automobile chassis and heavy machinery parts.

 

Cast iron is known for its high strength, good wear resistance and compressive resistance. In particular, gray cast iron has good liquid fluidity and is suitable for casting thin-walled castings with complex structures. In addition, through a special heat treatment process, the toughness of ductile iron has been significantly improved, even close to the level of cast steel, while maintaining the excellent wear resistance of cast iron, so it is widely used in high-strength structural parts such as engine crankshafts and gears.

 

Appearance and processing characteristics

 

From the appearance, the surface of cast steel is shiny, the structure is dense, and the particles are generally invisible to the naked eye; while cast iron is dark and gray, especially gray cast iron, whose surface particles are more obvious. In addition, steel castings will make a crisp "just" sound when they collide, which is significantly different from the sound of cast iron.

 

In terms of processing characteristics, the surface of steel castings is rough, and the riser and gate area are large, which usually needs to be cleaned by gas cutting and other methods. Although ductile iron can also be processed by cutting, its gas cutting performance is poor and it is not easy to be cut.

 

Application field

 

Due to its excellent mechanical properties, cast steel is widely used in fields with high requirements for strength and toughness, such as heavy machinery, shipbuilding, petrochemical equipment, etc. Cast iron occupies an important position in the manufacturing industry due to its low cost and stable performance, especially in the fields of automobile manufacturing, building materials, and pipeline systems. For example, modern water pipeline systems use a large number of cast iron materials because of their good corrosion resistance and pressure resistance.

 

In summary, there are significant differences between cast steel and cast iron in terms of chemical composition, physical properties, appearance characteristics and processing characteristics. These differences determine their unique advantages in different application fields. For manufacturers and engineers, understanding these differences helps to select the material that best suits specific needs, thereby improving product performance and reliability. With the advancement of science and technology and the development of the manufacturing industry, the application prospects of cast steel and cast iron will be broader.