Carbon steel is widely used in different industries. Its optimal hardness, durability, and versatility make it stand out. Various types of carbon steel offer unique properties. All kinds of carbon steel have iron in common. However, they primarily differ in the proportion of carbon content.
This carbon content difference results in variations in their use cases and overall value. Those carbon steels with a higher carbon proportion are robust and rigid. On the other hand, carbon with a lower carbon content is softer and more ductile. In this article, I’ll discuss four significant types of carbon steel. This piece will help you differentiate all the carbon steel types.
Overview of Carbon Steel
Before discussing types, let’s start with the basics of carbon steel material.
Carbon steel is primarily a type of steel and has iron as a base. However, its carbon content is a central alloy element present in it. The proportion of this carbon varies between 0.05% to 2%. This material also contains traces of other alloy cements. Those include manganese, silicon, sulfur, etc.
Steel is an alloy having iron as a base and carbon as a major alloy element. This steel alloy comes in various types, including stainless steel, alloy steel, and carbon steel. Both alloy steel and stainless steel have lower carbon proportions. However, the carbon steel has a higher carbon proportion compared to all other types, making it stand out.
Remember, carbon steel also has a higher iron proportion of around 95%. In fact, all the steel types have iron as their base. However, they differ in terms of the alloy elements. Here is the table showing the chemical composition of carbon steel:
| Element | Typical Range in Carbon Steel |
| Iron (Fe) | Balance (over 95%) |
| Carbon (C) | 0.05% – 2.0% |
| Manganese (Mn) | 0.30% – 1.5% |
| Silicon (Si) | up to 0.50% |
| Sulfur (S) | Less than 0.05% |
| Phosphorus (P) | Less than 0.05% |
The proportion of each alloy element can vary in different types of carbon steel. This material has its application in a wide range of industries. Some of those include plumbing, automobile, aerospace, construction, and so on. What makes carbon steel popular is its affordability. Additionally, this type of steel offers optimal durability and excellent machinability.
4 Types of Carbon Steel
As I mentioned earlier, carbon steel comes in various types. Those types vary from each other in terms of their carbon content. Those types with a higher carbon proportion are more durable, rugged, and hard to machine. Contrarily, other carbon steels with lower carbon proportions are softer but easier to machine.
Let’s discuss those types of carbon steel and their prominent advantages.
1- Low Carbon Steel
Low-carbon steel is also known as mild steel. It has a lower carbon content of around 0.05% and 0.30%. This low carbon proportion makes these carbon steel types highly ductile and soft. Due to lower carbon content, the price of this type is very low. Manufacturers use it to produce various products for everyday use. Those products are not very durable or robust.
However, they offer decent functionality for short-term users. As I said earlier, low-carbon steel is very soft and ductile. It offers excellent machinability and fabrication. Fabricators can cut, bend, shape, and drill it easily. Their fabrication does not require high-end machinery or cutting tools. Manufacturers employ several methods to enhance the strength and durability of their products.
Those include case hardening (carburizing) and galvanizing. In the case of hardening, the carbon is added to the surface of these materials. The addition of carbon increases the strength and supports it. Additionally, galvanizing increases the rust resistance of carbon steel. Additionally, manufacturers use several heat treatments, such as annealing, on this material. These additional treatments enhance the mechanical properties of carbon steel.
Advantages of Carbon Steel
The primary benefits of low-carbon steel are as follows:
- Low-carbon steel is very inexpensive. It is considered the best option for those with tight budgets who want steel products.
- The mild steel is soft and ductile. Therefore, it’s easier to bend, shape, and fabricate overall. You won’t need high-end machines for its fabrication.
- The availability of low-carbon steel is easier. Since this is very inexpensive, shops keep them in stock. You can easily buy it from any fabrication shop without having to go to a bigger city.
- The low-carbon steel has decent toughness due to the presence of manganese. It can absorb the force (energy) and does not break easily. However, you should not consider an application where extreme toughness is required.
- One of the primary advantages of low-carbon steel is its lightweight nature. Due to this, manufacturers use it to make products that are frequently used. It is used to make lightweight products with decent strength.
2- Medium Carbon Steel
This medium carbon steel has a higher carbon content, ranging from approximately 0.30% to 0.60%. This higher carbon content makes it a better option than mild steel. Additionally, it also contains manganese at approximately 0.60% and 1.65%. This higher manganese uplifts the value of medium carbon steel by making it tougher.
Due to better toughness, this carbon steel can absorb the energy when faced with impact. Additionally, its overall strength and hardness are superior when compared to low-carbon steel. What I like about this medium carbon steel is its midrange strength and ductility. Generally, material with higher strength and hardness has lower ductility.
Due to its decent ductility, this material offers excellent machinability. Additionally, it can undergo welding, enabling strong joints. However, you’ll use the correct welding technique to ensure a smooth welding experience. This material can undergo various heat treatments. These include quenching, tempering, annealing, and others. These treatments can increase the strength and structural integrity of this carbon steel.
Advantages of Medium Carbon Steel
Here is the list of benefits of medium carbon steel:
- Medium carbon steel has excellent toughness due to 0.60% and 1.65% of manganese
- This type of carbon steel can undergo tempering or quenching. So, its strength and ruggedness can be improved.
- The medium carbon steel offers decent machinability. However, you’ll still need some machining tools to get the job done.
- Creating a weld on this medium-carbon steel is relatively easy. You will be able to create a strong weld using a preheating technique.
- For the value it offers, I consider medium carbon steel to be cost-effective. Pipes made with carbon steel and other products are affordable. Their performance is as good as that of alloy steel.
3- High Carbon Steel
This type of carbon steel has a carbon portion of around 0.6% and 1.0%. Due to its higher carbon content, this type is very strong but brittle. Brittleness is something I don’t like, especially in carbon steel materials. Why? Because it makes the material sensitive to sudden impacts. If this higher carbon steel undergoes stress, it can break due to its higher brittleness.
However, its hardness is a key feature that makes it suitable for heavy-duty applications. Additionally, better hardness makes it more wear-resistant. However, its compromised flexibility and ductility are significant drawbacks. Due to limited ductility, machining of these materials is very challenging. The high-carbon steel cannot be bent or cut easily.
In fact, welding this higher carbon steel also poses some serious challenges. You’ll need dedicated machines and cutting tools for the fabrication of these materials. Manufacturers use dies, punches, and press brakes for their cutting, bending, and shaping. Additionally, this material can be heat-treated to increase its strength.
Both quenching and tempering can be helpful when it comes to heat treatment of this high-carbon steel. Due to its better hardness, this high-carbon steel offers excellent durability. It is used to make a wide range of cutting tools, thanks to its hardness. Those tools include blades, knives, and springs. Additionally, the cost of this material is higher than that of both medium and low carbon steel.
Advantages of High Carbon Steel
Here are some prominent advantages of higher carbon steel:
- High-carbon steel is known for its excellent strength and hardness. Due to this, products made with this carbon steel are long-lasting.
- It is suitable for products (knives or blades) that require sharp edges. This material has higher hardness, ensuring it can maintain its edges.
- The high-carbon steel offers improved fatigue resistance. It can withstand heavy but steady loads. Exposing high-carbon steel to sudden impacts can lead to its failure due to its high brittleness.
4- Ultra High Carbon Steel
This type of carbon steel has a carbon proportion between 1% to 2%. This higher content makes it more robust than all other types of carbon steel. However, this robustness never means you should prefer this type over other carbon steel types. Remember, each type has its unique value depending on its carbon content.
In this carbon steel, the carbon content can make cementite (iron carbide, Fe₃C). This formation of cementite further strengthens the structure of this carbon steel type. Both high and ultra carbon steel types have higher brittleness. However, the hardness of ultra-high carbon steel is very high due to the higher carbon proportion.
Due to brittleness, this ultra-carbon steel type is prone to chipping. This chipping is even more common if the carbon steel is subjected to a sudden impact. This material should only be used when extreme hardness is required. The machinability and weldability of this carbon steel are also very challenging. High-end machines and cutting tools are necessary for its fabrication.
Advantages of Ultra High Carbon Steel
Here are some pros of high carbon steel:
- Its strength is something that makes it stand out among all the carbon steel types. Additionally, ultra-high carbon steel lasts longer, even if used harshly.
- This material is robust and retains its edges for an extended period. In the old times, it was popular to make swords. Currently, it is used to make cutting tools and high-end knives.
- The ultra carbon steel has no premium alloy elements such as nickel. Due to this, the cost of this carbon steel is relatively lower. I consider it cost-effective, primarily due to its strength and durability.
- This carbon steel can withstand compressive force. When compressed, it can withstand the load. However, the compression should not be sudden. If you apply sudden compression, it can break this material due to its brittleness.
Which Type of Carbon Steel Should You Choose?
There is no one-size-fits-all answer when it comes to choosing carbon steel. Each product and project has unique material requirements. So you should analyze your needs and then select specific carbon steel types.
I recommend choosing low-carbon steel for budget-friendly products. Their strength and durability will be a bit compromised. This material is less brittle and easier to fabricate and machine. You can make coils, pipes, sheets, and other products using these materials. This type of carbon steel is a good starting point.
However, some products require more strength and durability. Right? In such a case, you should consider carbon steel over higher carbon steel. But the question is, how much carbon content is enough? That depends on the strength and hardness you need. Remember, the higher the carbon content, the higher will be the harndess and vice versa.
For most projects, medium carbon steel is an excellent option. This material is relatively easy to fabricate, which is a significant advantage. However, you can choose high or ultra-high carbon steel for making heavy-duty products. Here is the table showing the use cases of all these types of carbon steel:
| Type of Carbon Steel | Preferred Uses |
| Low-Carbon Steel | Construction beams, pipelines, automobile panels, coils |
| Medium-Carbon Steel | Gears, axles, shafts, railway tracks, machinery parts |
| High-Carbon Steel | Springs, cutting tools, knives, blades |
| Ultra-High Carbon Steel | Knives, dies, punches, specialty cutting tools |
Conclusion
Carbon steel is an essential material in different industries. In fact, its usage has become very popular in making cutting tools. However, this material comes in various types that differ from one another in terms of carbon content. Due to the difference in carbon proportion, each type offers a unique value proposition and performance.
In this article, I’ve explained four types of carbon steel. These types fit different use cases. Due to this, the selection of these carbon steel types can be tedious. If you prefer an inexpensive option, I would recommend choosing low-carbon steel. However, the medium carbon is the best option for moderate strength and price. The high and ultra carbon steel types are only suitable for heavy-duty cutting tools.