Which Is Better: Cast Steel or Carbon Steel Casting?

Investment casting can use a variety of materials, among which carbon steel castings and cast steel are two commonly used alloy materials. The carbon content is the most significant difference between the two. When the carbon content exceeds 2.1%, it is carbon steel for investment casting; otherwise, it is cast steel.

Characteristics of Cast Steel and Carbon Steel Castings

Both have the same chemical composition—they are ferrous metals composed of iron atoms. As is known, pure iron is very soft, so a certain amount of carbon is added to enhance its hardness. Steel is one of the most frequently used metals in the world.

• Carbon steel castings: Due to their load-bearing capacity and ductility, they are the first choice for many mechanical equipment and large components.

• Cast steel: Its ductility and load-bearing capacity may be inferior to those of carbon steel castings, but its corrosion resistance is much stronger. Equipment and parts made of carbon steel castings generally require little maintenance and have better durability.

Differences Between Cast Steel and Carbon Steel Castings

1. Corrosion Resistance

Carbon steel has stronger corrosion resistance than some other metals, but this does not prevent it from being corroded. We must still protect the products after production, such as painting or adding a protective layer. If the products we produce will be used in a more corrosive environment in the future, we can choose carbon steel casting. Alternatively, we can add chromium to prevent oxidation.

2. Cost

Typically, the purchase cost of raw steel is relatively high, so cast steel is cheaper than carbon steel. However, we must consider many factors:

• If we are producing short-term-use products that do not require a service life guarantee or post-maintenance, carbon steel is the best choice.

• If the product needs to ensure quality for 10, 20, or even more years, we also need to consider other costs such as post-maintenance and labor costs. In this case, choosing cast steel may be more cost-effective.

3. Ductility

Carbon steel has relatively good ductility, making it suitable for manufacturing high-quality products. Cast steel has slightly poorer ductility and fluidity, and more obvious shrinkage will occur during the cooling process.

4. Machinability (Flexibility)

Cast steel has lower hardness, so it has higher machinability. The highest-quality carbon steel castings are more difficult to machine than other materials, which is also related to their carbon content.

5. Vibration Damping

When selecting casting materials, damping characteristics should be considered, because the lack of damping capacity can lead to excessive vibration and noise (such as ringing or squealing). The graphite structure in cast iron—especially the flake structure in gray cast iron—is particularly beneficial for absorbing vibrations. This makes cast iron an ideal material for applications such as engine blocks and cylinder casings.

6. Compressive Strength

Compressive strength refers to the ability of a material to withstand forces that tend to reduce the size of an object. This is the opposite of the force that pulls the material apart. Compressive strength is very useful in mechanical applications where pressure and sealing are important considerations. The compressive strength of cast iron is usually higher than that of steel.

7. Wear Resistance

Due to its high carbon content, cast steel usually has better wear resistance. Its surface is more lubricious and less prone to wear.

Advantages of Carbon Steel and Cast Steel

Advantages of Carbon Steel Castings

Carbon steel for investment casting is also known for its corrosion resistance, especially when protective measures are taken during daily maintenance. In addition, it has the ability to resist deterioration, which makes the castings durable and extends their service life. The carbon content of cast steel or carbon steel (ranging from low-carbon steel and standard steel to high-carbon steel) usually determines the hardness of the material.

Advantages of Cast Steel

The true advantage of cast steel lies in its high design freedom—it can be used to manufacture parts with complex geometric shapes and hollow cross-sections.

Cast steel offers the greatest flexibility and variability in metallurgical manufacturing:

• It provides different heat treatment options and a wider range of mechanical properties and performance.

• We can also select different chemical compositions and control methods to meet various requirements of other projects.