St35.8 steel: A reliable choice for pressure-bearing pipelines

St35.8 is a type of steel for seamless steel pipes in the European standard (EN 10216-2) and is often used in the manufacture of pressure-bearing piping systems. Among them, "St" indicates structural steel, "35" represents the approximate value of tensile strength (about 350 MPa), and "8" indicates that this steel grade is suitable for pipes with a nominal outer diameter not exceeding 610 mm. It belongs to non-alloy quality steel. Through strict smelting and rolling processes, it meets the requirements of pressure pipelines for material safety and reliability. ​

This steel grade features excellent comprehensive mechanical properties, with a yield strength of approximately 235 MPa, a tensile strength ranging from 380 to 510 MPa, and an elongation of no less than 25%. It demonstrates moderate strength and outstanding plasticity, capable of withstanding pressure while adapting to certain deformations. It has good impact toughness, can resist impact loads at room temperature, and has excellent welding performance, which is convenient for the connection and installation of pipelines. In addition, the machinability and cold formability of St35.8 steel are also quite excellent, which can meet the requirements of different processing techniques. ​

In terms of chemical composition, St35.8 steel takes iron as the matrix, with the carbon content controlled at 0.12-0.20% to balance strength and toughness. The manganese content is 0.40-1.20%, which plays a role in strengthening the matrix. The silicon content does not exceed 0.55%, and it is used for deoxidation and improving the performance of steel. Phosphorus and sulfur, as harmful impurities, are respectively limited to below 0.025% and 0.020% to reduce the risks of cold brittleness and hot brittleness of steel. ​

St35.8 steel is mainly used in pressure-bearing pipeline systems for transporting water, steam, natural gas, oil and other media, such as thermal power networks, urban gas pipelines, and oil transportation pipelines. In the power industry, it can be used to manufacture the heat-receiving surface pipes and steam pipes of low-pressure boilers. In the chemical industry, it is suitable for pipelines transporting media with weak corrosiveness. Its reliable performance and good processability make it one of the widely used steels in the field of pressure-bearing pipelines. ​