Types of carbon steel

The classification of carbon steel is not isolated, they are interrelated and jointly determine the properties and applications of carbon steel. Understanding the classification of carbon steel is of great significance for us to choose and use carbon steel materials correctly. Whether in industrial production or daily life, carbon steel has made important contributions to our lives and social development with its diverse classifications and unique properties.

• Ordinary steel (S ≤ 0.050%, P ≤ 0.045%)

Ordinary steel is like an "affordable player", with relatively loose control over the content of impurities such as sulfur (S) and phosphorus (P). Although its quality may not be as good as high-quality steel and premium high-quality steel, its cost is lower and it is suitable for situations where quality requirements are not particularly high. For example, some ordinary building structures, daily necessities, etc., using ordinary steel can meet basic needs.

• High quality steel (S ≤ 0.035%, P ≤ 0.035%)

High quality steel is like a "quality improvement version player", with stricter control over the content of sulfur and phosphorus. This makes the performance of high-quality steel more stable and the quality better. In some situations where there are certain requirements for performance and quality, high-quality steel comes in handy. For example, manufacturing some mechanical parts, automotive components, etc., high-quality steel can ensure the reliability and durability of the products.

• High quality fine steel (S ≤ 0.025%, P ≤ 0.025%)

High quality steel is like a 'top player', with very strict standards for controlling the content of sulfur and phosphorus. This strict control enables high-quality steel to have very high purity and excellent performance. In some high-end fields, such as aerospace and precision instrument manufacturing, high-quality steel is an essential material. It can meet the requirements of high-performance and high-precision materials in these fields.

• Structural steel (with a carbon content generally less than 0.70%)

Structural steel is like the "skeleton" in architecture, mainly used to manufacture various engineering structures and mechanical parts. Due to its carbon content generally less than 0.70%, it has good strength and toughness, and can withstand large loads. In the field of architecture, structural steel is widely used for building bridges, high-rise buildings, etc; In the field of mechanical manufacturing, it is used to manufacture frames and components for various mechanical equipment.

• Tool steel (with a carbon content generally greater than 0.70%)

Tool steel is like a "sharp tool" in the hands of craftsmen, mainly used to manufacture various tools. Due to its high carbon content, it has high hardness and wear resistance. As mentioned earlier, cutting tools, measuring tools, etc. are all made of tool steel. Tool steel ensures that tools are not easily worn during use, maintaining sharp edges and precise dimensions.

• Boiling steel

Boiling steel is steel with incomplete deoxidation. During the smelting process, due to incomplete deoxidation, some gases may remain in the molten steel. These gases will produce boiling phenomenon during the solidification process of molten steel, so they are called boiling steel. The cost of boiling steel is relatively low, but its quality and performance are relatively poor. Its internal organization is not uniform enough, with some pores and impurities, so it is generally used in situations where quality requirements are not high.

• killed steel

Sedated steel is steel with a complete degree of deoxidation. During smelting, through sufficient deoxidation operation, the gas in the steel liquid is basically removed, and the steel liquid is relatively calm during solidification without boiling phenomenon. The internal structure of calm steel is uniform, with good quality and performance. It is suitable for occasions that require high quality and performance, such as manufacturing important mechanical parts, pressure vessels, etc.

• Special Sedative Steel

Special killed steel is a type of steel that has a more complete and thorough deoxidation degree than killed steel. Its quality and performance are superior, and its internal structure is more uniform and dense. Special killed steel is commonly used in fields that require extremely high material performance, such as aerospace, nuclear industry, etc. In these fields, the reliability and stability of materials are crucial, and special killed steel can meet these strict requirements.

The performance of carbon steel mainly depends on its chemical composition, and the main elements include:

• Carbon (C): Increases hardness and strength, reduces plasticity.
• Manganese (Mn): enhances hardness, improves weldability and impact toughness.
• Silicon (Si): increases strength, but excessive use can reduce plasticity and toughness.
• Sulfur (S) and phosphorus (P): usually present as impurities, excessive amounts can reduce the performance of steel.

The physical properties of carbon steel are mainly reflected in:

• Mechanical properties: including tensile strength, yield strength, hardness, and toughness.
• Heat treatment: Heat treatment such as annealing, normalizing, quenching, and tempering can be carried out to change the internal structure of the steel, thereby obtaining different properties.
• Weldability: Low carbon steel has good weldability, while high carbon steel is prone to cracking during welding due to its high hardness.

There are various processing techniques for carbon steel, including:
Cold processing: such as cold rolling, cold drawing, etc., can improve the strength and hardness of steel.
Hot processing, such as hot rolling, forging, etc., is usually carried out after heating to a certain temperature to obtain the desired shape and size.
Surface treatment, such as galvanizing, painting, or spraying anti-corrosion coatings, can improve the corrosion resistance of carbon steel.

Due to its excellent performance and economy, carbon steel is widely used in:

• Construction industry: used for building structures, support frames, steel beams, etc.
• Manufacturing industry: materials used as mechanical components, automotive parts, tools, and cutting tools.
• Infrastructure: occupies an important position in the construction of bridges, railways, and highways.
• Pipeline transportation: Low carbon steel pipes are widely used for transporting water, gas, etc.

Compared to other types of steel such as stainless steel, carbon steel has poorer corrosion resistance. But through surface treatment such as galvanizing or coating with special coatings, its ability to resist environmental factors can be improved to a certain extent.

Carbon steel meets the requirements of sustainable development due to its high recyclability and renewability. Waste carbon steel materials can be recycled and reused through melting and reprocessing, reducing resource consumption and environmental impact.

Carbon steel, as a fundamental industrial material, plays an important role in various fields. Through continuous research and improvement of its performance, its irreplaceability in modern industry has been ensured. With the advancement of technology and the strengthening of environmental awareness, the production and application of carbon steel will pay more attention to efficiency and sustainability