Steel grade indication of carbon steel pipe

Steel is an essential material in modern construction and manufacturing, and its properties can be tailored to meet specific requirements through variations in chemical composition and processing methods. The grade of steel is a critical identifier that communicates its mechanical properties, quality, and intended applications. This introduction will explore the steel grade indication of carbon steel pipe.

1. Carbon Structural Steel

① Designation: The grade is indicated by a combination of "Q" followed by a number, a quality grade symbol, and a deoxidation method symbol. The letter "Q" stands for the yield strength of the steel, and the number that follows represents the yield point in MPa. For instance, Q235 indicates a carbon structural steel with a yield point (σs) of 235 MPa.

② Quality and Deoxidation: Additional symbols may be included to denote the quality grade and the deoxidation method. Quality grade symbols are A, B, C, and D. The deoxidation method is indicated by F for boiling steel, B for semi-killed steel, Z for killed steel, and TZ for special killed steel. Killed steels typically do not require a mark, so ZT and TZ are not labeled. For example, Q235-AF signifies Grade A boiling steel.

③ Special-Purpose Carbon Steel: For specific applications like bridge or shipbuilding steel, the designation generally follows the same pattern as carbon structural steel, but with an additional letter at the end to indicate its specific use.

2. High-Quality Carbon Structural Steel

① Carbon Content: The first two digits of the grade indicate the carbon content in the steel, expressed in ten-thousandths of the average carbon content. For example, a steel with an average carbon content of 0.45% is designated as "45." This number does not indicate a sequence and should not be interpreted as gauge 45 steel.

② Manganese Content: For high-quality carbon structural steel with elevated manganese content, the symbol "Mn" is added to the grade, such as in "50Mn."

③ Boiled and Semi-Killed Steel: If the steel is boiled, semi-killed, or has a special purpose, this is indicated at the end of the steel grade. For example, a semi-killed steel with an average carbon content of 0.1% is labeled as "10b."

3. Carbon Tool Steel

① Designation: The grade is prefixed with "T" to distinguish it from other types of steel.

② Carbon Content: The number in the grade reflects the carbon content, expressed in thousandths of the average carbon content. For example, "T8" indicates a carbon content of 0.8%.

③ High Manganese Content: If the steel has a higher manganese content, "Mn" is added to the grade, such as "T8Mn."

④ High-Grade Steel: For high-quality carbon tool steel with lower phosphorus and sulfur content, the letter "A" is added to the grade, indicating a higher quality level, such as in "T8MnA."