LSAW Steel Pipes used for transporting high-temperature, high-pressure, and highly corrosive media need to have the following characteristics:

Mechanical property

High strength: able to withstand internal pressure stress in high temperature and high pressure environments, preventing pipeline rupture or deformation due to excessive pressure. Generally, it is required that the yield strength and tensile strength of steel pipes reach a high level, such as a yield strength of over 400MPa and a tensile strength of over 500MPa, to ensure the safety of the pipeline under extreme working conditions.

High toughness: The toughness of materials is particularly important under high temperature and high pressure conditions. Steel pipes should have good impact toughness and fracture toughness to prevent brittle fracture caused by stress concentration, medium impact, and other factors during operation. Through appropriate alloying design and heat treatment processes, the Charpy impact energy of steel pipes can meet relevant standard requirements at both room temperature and low temperature environments.

Creep resistance: Under long-term high temperature action, metal materials will undergo creep phenomenon, that is, slow plastic deformation. Therefore, steel pipes need to have excellent creep resistance to ensure the dimensional stability and strength reliability of the pipeline during its design service life. Steel pipes are usually made from steel containing alloying elements such as chromium, molybdenum, and tungsten, which can increase the recrystallization temperature of the material and enhance its creep resistance.

Corrosion resistance performance

Chemical corrosion resistance: For highly corrosive media such as acids, alkalis, salt solutions, etc., steel pipes must have good chemical corrosion resistance. Different corrosive media have different corrosion mechanisms on materials, so it is necessary to choose suitable corrosion-resistant materials based on the specific composition of the media. For example, for media containing chloride ions, stainless steel materials containing molybdenum, such as 316L stainless steel, can be selected, which can effectively resist pitting and crevice corrosion caused by chloride ions.

Electrochemical corrosion resistance: Steel pipes may undergo electrochemical corrosion in some high-temperature and high-pressure aqueous solution environments. In order to improve the electrochemical corrosion resistance of steel pipes, protective measures such as surface coating and lining anti-corrosion materials can be adopted. Common anti-corrosion coatings include epoxy powder coating, polyethylene coating, etc. These coatings can form a layer of isolation film on the surface of the steel pipe, preventing the medium from contacting the steel pipe substrate and thus playing a role in anti-corrosion. In addition, composite steel pipes lined with non-metallic materials such as rubber, plastic, and ceramics can also be used to further improve the corrosion resistance of the pipeline.

Processing and welding performance

Good processing performance: Steel pipes should be easy to cut, bend, weld and other processing operations to meet different pipeline system layouts and installation requirements. During the processing, steel pipes should maintain good dimensional accuracy and surface quality to avoid defects such as cracks and deformations. By optimizing the chemical composition and rolling process of steel, the processing performance of steel pipes can be improved, enabling them to adapt to various complex processing techniques.

Excellent welding performance: Welding is a key link in the pipeline installation process, and the welding performance of steel pipes directly affects the overall quality and reliability of the pipeline. LSAW steel pipes used for transporting high-temperature, high-pressure, and highly corrosive media should have good weldability, which means that welding defects such as cracks, pores, and slag inclusions are not easily generated during welding, and the weld metal should have good matching with the base metal, ensuring that the strength and corrosion resistance of the weld are not lower than those of the base metal. Generally, the welding performance of steel pipes is improved by controlling the carbon equivalent in the steel, adding appropriate alloying elements, and using advanced welding processes and welding materials.

Dimensional accuracy and surface quality

High precision dimensions: In high-temperature and high-pressure pipeline systems, the dimensional accuracy of steel pipes directly affects the connection sealing and fluid transport efficiency of the pipelines. The outer diameter, wall thickness, ovality and other dimensional parameters of steel pipes should be strictly controlled within the allowable tolerance range to ensure precise docking and good sealing performance between pipelines. Generally, the outer diameter tolerance of steel pipes is required to be controlled within ± 0.5%, and the wall thickness tolerance is required to be controlled within ± 10%.

Good surface quality: The surface of the steel pipe should be smooth and free of obvious defects such as cracks, folds, scratches, and pitting. Good surface quality can not only improve the corrosion resistance of steel pipes, but also reduce the flow resistance of fluids in pipelines and improve transportation efficiency. During the production process, strict surface treatment techniques such as acid washing, shot blasting, etc. are used to remove impurities such as oxide scale and rust on the surface of the steel pipe. At the same time, non-destructive testing is performed on the steel pipe to ensure that the surface quality meets relevant standard requirements.

Stability and reliability

Thermal stability: In high temperature environments, the microstructure and properties of steel pipes should remain stable and not significantly deteriorate due to temperature changes. Through reasonable alloy design and heat treatment processes, steel pipes have good oxidation resistance and structural stability at high temperatures, preventing phenomena such as grain growth and phase transformation, thereby ensuring that the mechanical properties and corrosion resistance of steel pipes are not affected.

Long term reliability: Pipeline systems that transport high-temperature, high-pressure, and highly corrosive media typically require a long service life, so steel pipes need to have long-term reliability. This requires strict control over the selection, production, installation, use, and maintenance of steel pipes to ensure their long-term stable operation under harsh working conditions. By conducting strict quality inspection and performance testing on steel pipes, as well as establishing a comprehensive pipeline monitoring and maintenance system, potential problems with steel pipes can be identified and addressed in a timely manner, extending the service life of the pipes and ensuring the safe and reliable operation of the entire system.