GB 20# seamless steel pipe

20# carbon steel belongs to high-quality low-carbon steel in national standard metal materials. Because of its good toughness, plasticity and weldability, it has wide application in China's petrochemical industry, and different 20 carbon steel materials are used. The incidence is also high. However, in fact, different carbon steels of different size 20 have different chemical compositions and manufacturing methods, and their mechanical properties are different. Care must be taken when substituting materials.

Corresponding major American standards are: Standard Specification for Pipe, Steel, Black and Hot - Dipped, Zinc - Coated, Welded and Seamless ( ASTM A53 - 12) and StandardSpecification for Seamless Carbon Steel Pipe for High Temperature Service ( ASTM A106 - 15).

Among the steel tubes, manganese (Mn), silicon (Si), sulfur (S), phosphorus (P), and carbon (C) are the main controlled elements that determine the properties of the steel. In addition to C, the content of P and S is always the key point to determine the performance of steel. High P content will lead to “cold brittleness”, and high S content will lead to “hot brittleness”.

The standard for seamless steel tubes for high pressure and petroleum cracking (GB5310-2008, GB 6479-2013, GB 9948-2013) is for high-quality carbon steel. The control values for harmful elements P and S are obviously stricter than those for low and medium pressure boilers. Seamless steel pipes for conveying fluids (GB 3087-2008, GB /T 8163-2008), this will also improve the hydrogen resistance and welding performance of the pipe. The ASTM standard requires S-content requirements for materials that are close to low- and medium-pressure boilers and seamless steel tubes for conveying fluids(GB 3087—2008, GB/T 8163—2008). However, it is significantly higher than the standard for seamless steel tubes for high pressure and petroleum cracking (GB 5310-2008, GB 6479-2013, GB 9948-2013), and the ASTM standard has low control of P elements.

The strength of C determines the strength of steel. The strength of GB 20 carbon steel pipe is not much different, and the stiffness of ASTM standard carbon steel pipe is obviously higher than the national standard. The presence of Cr and Cu can significantly increase the strength of the steel. ASTM carbon steel materials are relatively stronger than national standards.

Mn is mainly added as a deoxidizer in carbon steel, which can improve the “cold brittleness” and “hot brittleness” and contribute to the improvement of yield strength and tensile strength. ASTM standard materials are also significant at this point. Better than national standard materials.

On the whole, the chemical composition control of national standard materials is stricter than ASTM standard materials. Its Chinese standard GB 5310-2008, GB 6479-2013 and GB 9948-2013 have the best anti-corrosion and anti-hydrogen properties, but the strength of ASTM is more advantageous.