Brief Overview of The Popular Types of Carbon Steel in 2024

Introduction

Carbon steel is an iron-carbon alloy with a carbon content of 0.0218%-2.11%. It generally contains small amounts of silicon, manganese, sulfur, and phosphorus. The higher the carbon content in carbon steel, the greater the hardness and strength, but the lower the plasticity. 

There are different ways to classify carbon steel. According to the use, carbon steel can be divided into three categories: carbon structural steel, carbon tool steel and free-cutting structural steel. Carbon structural steel is further divided into two types: engineering construction steel and machine-made structural steel. 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 quality of steel, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur content), high-quality carbon steel (low phosphorus and sulfur content) and high-grade high-quality steel (lower phosphorus and sulfur content).

Carbon Structural Steel

This popular type of carbon steel mainly ensures mechanical properties. Therefore, its grade reflects its mechanical properties and is expressed by “Q+ numbers”. The numbers indicate the yield point value. For example, Q275 indicates that the yield point is 275Mpa. If the letters A, B, C, and D are marked after the grade, it means that the quality of the steel is different. The amount of S and P decreases in order, while the quality of the steel increases in order. If the letter "F" is marked after the grade, it is boiling steel, if it is marked "b", it is semi-killed steel, and if it is not marked "F" or "b", it is killed steel. Carbon structural steel is generally not heat treated and is used directly as supplied.

Carbon Tool Steel

Carbon tool steel is a high-carbon steel that basically does not contain alloy elements. This popular type of carbon steel has a carbon content in the range of 0.65%-1.35%. It has low production costs and the source of raw materials is easy to obtain. Besides, its cutting processability is good. After heat treatment, it can obtain high hardness and wear resistance, so it is a widely used steel type for manufacturing various cutting tools, molds, and measuring tools. However, this type of carbon steel has poor red hardness. When the working temperature is greater than 250°C, the hardness and wear resistance of the steel will drop sharply and it will lose its working ability. In addition, carbon tool steel is not easy to harden if it is made into larger parts, and is prone to deformation and cracks.

Free-cutting Structural Steel

Free-cutting structural steel, as another popular carbon steel, is made by adding some elements to the steel that make the steel brittle, so that the steel is easily broken into chips when cutting, which is beneficial to increasing the cutting speed and extending the tool life. The element that makes steel brittle is mainly sulfur. Elements such as lead, tellurium, and bismuth are often used in ordinary low-alloy free-cutting structural steel. The sulfur content of this steel is in the range of 0.08%-0.30%, and the manganese content is in the range of 0.60%-1.55%. Sulfur and manganese in steel exist in the form of manganese sulfide. Manganese sulfide is very brittle and has lubricating properties, making the chips easy to break and helping to improve the quality of the machined surface.

High-Quality Structural Steel

High-quality structural steel must ensure both chemical composition and mechanical properties. Its grade is a two-digit number representing the mass fraction of the average carbon in the steel. For example, 35 steel means that the average carbon mass fraction in the steel is 0.35%. This popular type of carbon steel is mainly used to make machine parts. Generally, heat treatment is required to improve mechanical properties. It has different uses depending on the carbon mass fraction.

Ordinary Low-alloy Steel

Ordinary low alloy steel is a common alloy steel containing a small amount of alloying elements (the total amount does not exceed 3% in most cases). This kind of steel has relatively high strength, good comprehensive properties, corrosion resistance, wear resistance, low temperature resistance, as well as good cutting performance and welding performance. Its service life and range of use far exceed that of carbon steel. Ordinary low alloy steel can be smelted in open hearth or converter using general smelting methods, and the cost is close to that of carbon steel.

Alloy Steel For Engineering Structures

This refers to alloy steel used in engineering and building structures, including weldable high-strength alloy structural steel, alloy steel, alloy steel for railways, alloy steel for geological oil drilling, alloy steel for pressure vessels, high manganese wear-resistant steel, etc. This type of carbon steel is used as engineering and construction structural parts. Among alloy steels, the total alloy content of this type of steel is low, but its production and use are large.  

Alloy Steel For Mechanical Structures

This popular type of carbon steel refers to alloy steel suitable for manufacturing machines and mechanical parts. It is based on high-quality carbon steel and appropriately adds one or several alloying elements to improve the strength, toughness and hardenability of the steel. This type of steel is usually heat treated before use. It mainly includes two categories of commonly used alloy structural steel and alloy spring steel, including quenched and tempered alloy steel, surface hardened alloy steel, and alloy steel for cold plastic forming.

Alloy Structural Steel

The carbon content of alloy structural steel is lower than that of carbon structural steel, generally in the range of 0.15%-0.50%. In addition to carbon, it also contains one or several alloying elements, such as silicon, manganese, vanadium, titanium, boron and nickel, chromium, molybdenum, etc. Alloy structural steel is easy to harden and not easy to deform or crack, making it easy to heat treat to improve the performance of the steel. Alloy structural steel is widely used in the manufacture of various transmission parts and fasteners for automobiles, tractors, ships, steam turbines, and heavy machine tools. Low carbon alloy steel generally undergoes carburizing treatment, while medium carbon alloy steel generally undergoes quenching and tempering treatment. 

Alloy Tool Steel

Alloy tool steel is medium and high carbon steel containing a variety of alloying elements, such as silicon, chromium, tungsten, molybdenum, vanadium, etc. Alloy tool steel is easy to harden and is not prone to deformation and cracks. It is suitable for manufacturing cutting tools, molds and measuring tools with large sizes and complex shapes. The carbon content of alloy tool steel is also different for different uses. The carbon content of most alloy tool steels is 0.5%-1.5%. The carbon content of hot deformation mold steel is lower, in the range of 0.3%-0.6%; the carbon content of cutting tool steel is generally about 1%. Cold working mold steel has a higher carbon content, such as graphite mold steel with a carbon content of 1.5%, and high carbon and high chromium cold working mold steel has a carbon content of more than 2%.

High-speed Tool Steel

High-speed tool steel is a high-carbon high-alloy tool steel. The carbon content in this popular type of carbon steel is 0.7%-1.4%. The steel contains alloy elements that can form high-hardness carbides, such as tungsten, molybdenum, chromium, and vanadium. High-speed tool steel has high red hardness. The hardness does not decrease even at temperatures as high as 600°C under high-speed cutting conditions, thus ensuring good cutting performance.

Carbon Spring Steel

Carbon spring steel is high-quality carbon structural steel with a carbon content in the range of 0.6%-0.9%. Spring is used under impact, vibration or long-term alternating stress, so carbon spring steel is required to have high tensile strength, elastic limit and high fatigue strength as a popular carbon steel. On the contrary, alloy spring steel is mainly silicon-manganese steel type. Their carbon content is slightly lower, and their performance is mainly improved by increasing the silicon content.

Summary

The above concludes the popular types of carbon steel across the globe in 2024. It is critical to have a deep understanding of your own needs or your clients’ specific needs and expectations when deciding on which type of carbon steel to purchase. Each common type of carbon steel consists of quite a number of specific grades that have their own characteristics and settings of use.

As a leading manufacturer and supplier of steel products with more than 20 years professional experience in this field, Jiuzhou Metal is committed to manufacturing and offering a wide range of popular types of carbon steel. The company has passed ISO9001 quality management system certification and CE certification. All the products can be executed according to ASTM, JIS, DIN, BS and other common international standards. At Jiuzhou Metal, we always give great importance to optimizing our products and services, and prioritize the needs of our clients. Nowadays, more and more fellows worldwide seek assistance from Jiuzhou Metal in meeting their demands for carbon steel, and thus fueling their business development!