Carbon Steel Pipe Material Grade

Carbon steel pipe is one of the most widely used steel pipe types in industrial piping systems, especially in the oil and gas, chemical, power, boiler, building structure, and machinery manufacturing sectors, where it occupies a core position.

In international trade and engineering applications, a correct understanding of the material grades, standard systems, and performance differences of carbon steel pipes is crucial for selection, pricing, and quality control.

Carbon Steel Pipe Material Code

Different countries and standards systems use different methods to represent the material of carbon steel pipes, but they all essentially revolve around mechanical properties, chemical composition, and operating conditions. The carbon steel pipe material code typically includes information on material type, strength grade, or chemical composition:

1. Letter + Number Combination (e.g., A106B)

Letters represent standards or applications (A=ASTM, X=pipeline steel), and numbers represent strength or composition codes.

A106 does not indicate a "corrosion resistance grade," but rather a standard for seamless carbon steel pipes for high-temperature.

In API 5L, X represents the minimum yield strength (ksi).

2. Combinations of numbers and symbols (e.g., Q345R)

Q represents yield strength, 345 is the yield value (MPa), and R indicates it's for pressure vessels (GB 713-2014).

Q345R is specifically for pressure vessels and boilers (GB 713), not ordinary structural steel.

Carbon Steel Pipe Material Types

1. Mild Steel Pipe

Mild steel pipes are mainly made of steel with low carbon content, possessing lower strength and hardness, but better toughness and weldability.

These carbon steel pipes are suitable for applications where high strength requirements are not necessary, such as transporting low-pressure fluids or serving as structural support.

2. Medium-Carbon Steel Pipe

Medium-carbon steel pipes have a moderate carbon content, thus possessing moderate strength and hardness. These carbon steel pipes maintain good toughness and weldability while withstanding certain pressure.

Medium carbon steel pipes are widely used in various industrial fields, such as petroleum, chemical, and power.

3. High Carbon Steel Pipe

High carbon steel pipes are made of steel with a higher carbon content, thus possessing higher strength and hardness. However, high carbon steel pipes have relatively poor toughness and weldability.

These types of carbon steel pipes are typically used in applications requiring high pressure or high wear, such as oil drilling and mining.

Carbon Steel Pipe Material Standards

Carbon steel pipes are a commonly used metal material, widely applied in petrochemical, power, construction, and manufacturing fields. Therefore, carbon steel pipe standards are of great importance. The following are relevant standards for carbon steel pipe materials:

1. International Standards

International standards for steel pipes include ISO, ASTM, DIN, etc., with ISO standards being the most commonly used. ISO standards specify the dimensions, shape, quality, and other requirements for seamless and welded carbon steel pipes, alloy seamless steel pipes, and alloy welded steel pipes. These standards play an important role in international trade and technical exchange.

2. American Standards

American steel pipe standards include ASTM and API. ASTM standards refer to a series of steel standards specifying various types and grades of steel pipe materials. API standards are mainly used for steel pipes in the oil and gas industry, including API 5L and API 5CT, for applications such as drill pipe and casing.

A106: Seamless carbon steel pipe for high-temperature applications, divided into three grades: A, B, and C. For example, A106B has a yield strength ≥240 MPa (ASTM A106-19).

A53: Welded/seamless steel pipe, divided into A (welded) and B (seamless) types. A53B has a tensile strength ≥415 MPa.

3. Chinese Standards

Chinese national standards integrate international and Chinese standards, formulating a series of specific standardized specifications. Chinese steel pipe standards mainly include GB/T, JB/T, SY/T, DL/T, etc. Among them, GB/T standards are the most widely used, covering steel standards for various industries.

Q235: Ordinary carbon structural steel, yield strength ≥235 MPa (GB/T 700-2006). 20# Steel: High-quality carbon steel, tensile strength ≥410 MPa (GB/T 8163-2018).

Carbon Steel Pipe Material Grades

Carbon steel exhibits different properties under varying temperatures and pressures; therefore, steel pipe grades are determined based on the material's mechanical properties and chemical composition.

There are three main classification standards for carbon steel pipe materials: American, European, and Chinese. The United States uses the ASTM standard, Europe uses the EN standard, and China uses the GB/T standard. The following are the grade classifications for each standard:

1. ASTM Standards Classification of Carbon Steel Materials

ASTM standards classify carbon steel materials into four grades: A, B, C, and D. Higher grades indicate better strength and corrosion resistance. Certain ASTM-grade mild steel pipes are widely used in fluid transportation, equipment structures, and hydraulic systems.

2. EN Standard Classification of Carbon Steel Materials

The EN standard classifies carbon steel materials into six grades: P195TR1, P195TR2, P235TR1, P235TR2, P265TR1, and P265TR2. Higher grades generally indicate better strength and corrosion resistance.

3. GB/T Standard Classification of Carbon Steel Materials

The GB/T standard classifies carbon steel materials into ten grades: Q195, Q215A, Q215B, Q235A, Q235B, Q235C, Q235D, Q275, Q345, and L245. Higher grades generally indicate better strength and corrosion resistance.

4. Comparison Chart of Mainstream Carbon Steel Pipe Material Grades

The Role of Carbon Steel Pipe Material Grade

The grade of carbon steel pipe material determines the environment and liquid (gas) medium it can be used for. For specific environments and liquid (gas) media, the appropriate carbon steel pipe material grade must be selected. At the same time, the grade of carbon steel pipe material also determines the load-bearing capacity and service life of the pipeline.

Carbon Steel Pipe Material Specification Chart

The following is a table of carbon steel pipe material specifications parameters, which summarizes the commonly used carbon steel pipe material grades and their corresponding specifications parameters.

FAQ

1. Is there a difference in material grades between carbon steel pipes and seamless carbon steel pipes?

There is no fundamental difference.

The material grade of carbon steel pipes is determined by the material standard, not by the manufacturing process (seamless or welded).

Seamless carbon steel pipes: Common materials are ASTM A106 Gr.B, 20#, and API 5L X52.

Welded carbon steel pipes: Common materials are ASTM A53 Gr.B and Q235. Whether to choose seamless pipes mainly depends on pressure, temperature, and safety requirements.

2. What do A, B, and C represent in the carbon steel pipe material grades?

In ASTM standards: A, B, and C represent different performance grades under the same standard. Higher grades indicate better strength and temperature resistance.

For example, in ASTM A106:

Gr.A: Low strength;

Gr.B: Most commonly used;

Gr.C: High strength (less commonly used).

3. How to choose the appropriate carbon steel pipe material grade?

It is recommended to consider the following five aspects: Design pressure and temperature; Transport medium (oil, gas, water, steam); Whether seamless carbon steel pipes are required; Project implementation standards (ASTM / EN / GB); Whether export or third-party inspection is required (SGS / BV / TUV).

Summary

The material grade of carbon steel pipes is not simply a distinction of "high or low strength," but a comprehensive result of standard systems, chemical composition, mechanical properties, and the usage environment.

In practical procurement and engineering applications, the following factors should be considered: operating temperature and pressure, conveying medium, and international or owner-specified standards. Scientific selection of the material quality grade of carbon steel pipes or seamless carbon steel pipes is crucial to ensuring project safety, compliance, and optimal cost.

Read more: Types of seamless carbon steel pipes or Thermal conductivity of carbon steel pipe