Carbon Steel and Stainless Steel: What’s the difference?

Carbon steel and stainless steel are two common types of steel we encounter in our daily lives, and they differ in many respects. Understanding the differences between them can help us better choose and use the appropriate materials. This article will detail the differences between carbon steel and stainless steel, so that you can better understand and apply these two materials.

What is carbon steel?

It mainly refers to the steel whose mechanical properties depend on the carbon content in the steel, and generally does not add large amounts of alloying elements. Sometimes it is also called plain carbon steel or carbon steel. Carbon steel refers to iron-carbon alloys with a carbon content of less than 2%.

Carbon steel, besides containing carbon, typically also contains small amounts of silicon, manganese, sulfur, and phosphorus.

Carbon steel can be divided into three categories according to uses: carbon structural steel, carbon tool steel, and easy-cutting structural steel. Carbon structural steel can be further divided into two types: building structural steel and machine-manufacturing structural steel.

Carbon steel can also be divided according to their smelting methods: open hearth steel, converter steel, and electric furnace steel.

According to their deoxidation methods, carbon steel can be divided into: rimmed steel（F）, killed steel（Z）, semi-killed steel（b）, and special killed steel（TZ）.

According to the carbon content, carbon steel can be divided into: low-carbon steel (WC ≤ 0.25%), medium-carbon steel (WC0.25%-0.6%), and high-carbon steel (WC>0.6%).

According to the phosphorus and sulfur content, carbon steel can be divided into: ordinary carbon steel (with higher phosphorus and sulfur content), high-quality carbon steel (with lower phosphorus and sulfur content), and advanced high-quality steel (with even lower phosphorus and sulfur content) and extra high-quality steel.

Generally, as the carbon content in carbon steel increases, the harder and stronger it becomes, but the plasticity decreases.

What is stainless steel?

It is composed of two main parts: stainless steel and acid-resistant steel. In short, the steel that can resist atmospheric corrosion is called stainless steel, while the steel that can resist corrosion of chemical media is called acid-resistant steel. Stainless steel is a high alloy steel with more than 60% iron as the base material, and added chromium, nickel, molybdenum, and other alloying elements.

When the chromium content in the steel exceeds 12%, the steel is not easy to corrode and rust in the air and dilute nitric acid. The reason is that chromium can form a very tight oxide film on the surface of the steel, effectively protecting the steel from corrosion. The chromium content in stainless steel usually exceeds 14%, but stainless steel is not absolutely rust-free. In coastal areas or some places with serious air pollution, when the chloride ion content in the air is relatively large, the exposed surface of stainless steel in the atmosphere may have some rust spots, but these rust spots are limited to the surface and will not corrode the base body inside the stainless steel.

In general, when the Wcr content of chromium exceeds 12%, the steel has the characteristics of stainless steel. Stainless steel can be divided into five categories according to the microstructure after heat treatment: ferrite stainless steel, martensitic stainless steel, austenitic stainless steel, austenite-ferrite stainless steel and precipitation carbide stainless steel.

Stainless steel is usually divided into four categories according to the base structure:

1. Ferrite stainless steel. Chromium content is 12% to 30%. Its corrosion resistance, toughness, and weldability improve with the increase of chromium content. Its chloride stress corrosion resistance is better than other types of stainless steel.
2. Austenitic stainless steel. Chromium content is greater than 18%, and it also contains about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. It has good comprehensive performance and can withstand corrosion of various media.
3. Austenite-ferrite dual-phase stainless steel. It has the advantages of both austenite and ferrite stainless steel, and also has superplasticity.
4. Martensitic stainless steel. It has high strength, but poor ductility and weldability.

Carbon Steel and Stainless Steel: What’s the difference?

Carbon Steel and Stainless Steel exhibit several significant differences, primarily in their composition, properties, applications, and costs. Here is a detailed analysis of the differences between the two:

Composition and Appearance:

1. Carbon Steel: Primarily composed of iron and carbon, with a carbon content ranging from 0.12% to 2.0%. Due to its high carbon content, carbon steel often has a dark black appearance with a dull surface, lacking the smoothness and shine of stainless steel.
2. Stainless Steel: Primarily composed of chromium and nickel, with a chromium content of at least 10.5% and a carbon content not exceeding 1.2%. Stainless steel products typically have a silvery bright appearance with a smooth and shiny surface.

Corrosion Resistance:

1. Carbon Steel: Unable to form an oxide chromium layer on its surface, carbon steel has poor corrosion resistance and is prone to rusting.
2. Stainless Steel: Due to its high chromium content, chromium reacts with oxygen to form an oxide chromium layer on the surface of stainless steel, preventing corrosion. Therefore, stainless steel has superior corrosion resistance compared to carbon steel.

Wear Resistance:

1. Carbon Steel: With high hardness and low plasticity, carbon steel exhibits good wear resistance and is often used in the manufacture of cutting tools and abrasives.
2. Stainless Steel: Compared to carbon steel, its wear resistance is slightly inferior.

Magnetic Properties:

1. Carbon Steel: Highly magnetic due to its primary composition of iron.
2. Stainless Steel: Mostly non-magnetic or weakly magnetic due to the presence of nickel, which inhibits or removes the magnetic properties of the material.

Ductility:

1. Carbon Steel: Due to its low nickel content, carbon steel has relatively poor ductility.
2. Stainless Steel: With a high nickel content, stainless steel exhibits excellent ductility, surpassing carbon steel in this aspect.

Applications:

1. Carbon Steel: Due to its high strength, good wear resistance, ease of processing, and relatively low cost, carbon steel is commonly used in the manufacture of various mechanical parts, tools, bearings, cutting tools, abrasives, and more.
2. Stainless Steel: With its excellent corrosion resistance, ductility, and aesthetically pleasing appearance, stainless steel is widely used in applications such as security grilles, kitchenware, and certain specialized items.

Cost:

1. Carbon Steel: With fewer alloys added during production, carbon steel has a relatively lower cost.
2. Stainless Steel: The addition of a significant amount of alloys during production results in a higher cost and a more expensive price for stainless steel.

Conclusion

Thank you for reading our article and we hope it can help you to have a better understanding of the differences between carbon steel and stainless steel. If you want to learn more about carbon steel and stainless steel, we’d advise you to visit Huaxia Steel for more information.

As a leading supplier of carbon steel across the world, Huaxia Steel provides customers with a wide range of high-quality products such as alloy steel, tool steel, carbon steel, carbon steel tubes, and carbon steel pipes for global markets at a very competitive price.