What is Carbon Steel? Distinguishing Carbon Steel from Stainless Steel

In the world of construction materials and manufacturing, steel has always been a core element, playing an indispensable role in every project. However, among numerous steel types, carbon steel and stainless steel are the two most frequently mentioned. The question is, do you truly understand the difference between these two materials? In the article below, Son Ha SSP will delve into carbon steel, its classifications and characteristics, and compare it with stainless steel to help you choose the most suitable steel for your needs.

What is Carbon Steel?

Carbon steel is an alloy of iron (Fe) and carbon (C). It may also contain small amounts of other elements such as manganese (up to 1.65%), silicon (up to 0.6%), sulfur, or phosphorus, but carbon is still the determining factor for the steel’s main properties.

Carbon steel is an alloy of Fe and C

In carbon steel, the carbon content determines the steel’s properties. Higher carbon content results in harder steel but also makes it more brittle, meaning reduced ductility. Conversely, lower carbon content results in more ductile and softer steel. This allows this material to be flexibly applied in various fields such as construction, industrial manufacturing, and machinery fabrication.

Another notable characteristic of carbon steel is that its cost is usually lower than stainless steel, but its corrosion resistance is poorer. Therefore, if not protected or used properly, it is susceptible to corrosion in humid environments.

Classification of Carbon Steel

Carbon steel is not a single type. Based on carbon content and application properties, this material is divided into the following main types:

2.1. Plain Carbon Steel

Plain carbon steel (low carbon steel) is a type of steel with low carbon content (below 0.25%). It is easy to process, bend, and weld, suitable for applications that do not require high strength, such as making door frames, roofing sheets, or pipes. The cost of plain carbon steel is also lower than other types, helping to save production costs.

Plain carbon steel is divided into three main categories:

• Type A: Steel evaluated by mechanical properties such as strength, hardness, and ductility.
• Type B: Steel evaluated by chemical composition (elemental composition, high or low ratios).
• Type C: Steel evaluated by both of the above factors.

2.2. Tool Steel

This type of steel contains medium to high carbon content (0.55% – 1.5%) and is used to manufacture tools such as knives, scissors, or molds. The characteristics of tool steel are hardness and good wear resistance, but it is more difficult to process due to its high brittleness.

2.3. Structural Steel

Structural steel usually has a medium carbon content and is used in the construction of bridges, high-rise buildings, and structures bearing large loads. Its characteristics are good tensile strength, moderate hardness, and high load-bearing capacity, making it suitable for important, key, and heavily stressed machine parts such as gears, shafts, and rollers.

Carbon steel often has good tensile strength and good hardness

2.4. Mild steel 

Mild steel is a term used to refer to low carbon steel with a carbon content below 0.25%. Unlike other alloys, mild steel does not contain elements such as chromium or nickel. It is the most common type of steel on the market today because it is easy to process and has a low cost. However, the corrosion resistance of mild steel is quite limited, so it needs to be painted or coated to increase its lifespan.

Comparison of Carbon Steel and Stainless Steel

Carbon steel and stainless steel are both widely used materials, but each has its own advantages and disadvantages, suitable for different purposes. Below is a comparison table of the composition, physical properties, machinability, and applications of these two types of steel:

3.1. Durability and Corrosion Resistance

Stainless steel is superior to carbon steel in terms of corrosion resistance, especially in humid or chemical environments. Conversely, carbon steel is prone to rust if not coated or painted for protection.

3.2. Load-Bearing Capacity

Carbon steel has higher hardness than stainless steel, suitable for applications requiring high load-bearing capacity and tensile strength. However, stainless steel has better ductility, helping to resist impact and prevent easy breakage.

3.3. Aesthetics

If you need a material with a shiny, luxurious surface, stainless steel is the optimal choice. Carbon steel usually has a duller surface and is not suitable for high aesthetic requirements.

Conclusion

The choice between carbon steel and stainless steel depends on the specific requirements of the project. If you need a low-cost, easy-to-process, and strong material, carbon steel is an ideal solution. Meanwhile, if durability, corrosion resistance, and aesthetics are prioritized, stainless steel will be the perfect choice.

Understanding the difference between carbon steel and stainless steel not only helps you make the right decision but also optimizes the efficiency and cost of your project. Consider carefully to achieve the best results!