Application of stainless steel tubing in petroleum and petrochemical industry
Stainless steel according to the chemical composition can be divided into Cr stainless steel, CR-Ni stainless steel, CR-Ni-Mo stainless steel, according to the application field can be divided into medical stainless steel, atmospheric corrosion resistant stainless steel, anti-oxidation stainless steel, Cl – corrosion resistant stainless steel. But the most commonly used classification is according to the structure of steel to classify, generally can be divided into ferritic stainless steel, austenitic stainless steel, martensitic stainless steel, duplex stainless steel and precipitation hardening stainless steel. In petroleum and petrochemical applications, austenitic stainless steel, ferritic stainless steel and duplex stainless steel account for a large proportion.
Ferritic stainless steel Cr content in general between 13%-30%, C content is generally less than 0.25%, through annealing or aging, carbide in the ferritic grain boundary precipitation, so as to achieve corrosion resistance. Generally speaking, the corrosion resistance of ferritic stainless steel is lower than austenitic stainless steel and duplex steel, but higher than martensitic stainless steel. But because of its low production cost compared with other stainless steel, therefore, in the chemical and petrochemical applications, for corrosion resistant medium and strength requirements are not high in the field of application scope. Such as in sulfur oil, hydrogen sulfide, room temperature nitric acid, carbonic acid, hydrogen ammonia mother liquor, urea production of high-temperature ammonia, urea mother liquor and vinylon production of vinyl acetate, acrylonitrile and other environments are widely used.
The general Cr content of martensitic stainless steel is between 13%-17%, and the C content is higher, between 0.1% and 0.7%. It has higher strength, hardness and wear resistance, but the corrosion resistance is lower. It is mainly used in the petroleum and petrochemical field in the environment where corrosive medium is not strong, such as high toughness and impact load components, such as steam turbine blades, bolts and other related parts and components.
The content of Cr in austenitic stainless steel is between 17%-20%, the content of Ni is between 8%-16%, and the content of C is generally lower than 0.12%. The austenitic structure can be obtained at room temperature by adding Ni to expand the austenitic transformation area. Austenitic stainless steel corrosion resistance, plasticity, toughness, processing performance, welding performance, low temperature performance compared to other stainless steel are more excellent, so its application in various fields is also the most extensive, its use of about 70% of the total amount of all stainless steel. In the field of petroleum and petrochemical, strong corrosive medium and low temperature medium, advantages of austenitic stainless steel is larger, such as high corrosion resistance, especially the inner component in the resistance to intergranular corrosion environment, like heat exchanger/pipe fittings, cryogenic liquefied natural gas (LNG) pipeline, such as urea, sulfur ammonia production container, flue gas dust removal and desulfurization device.
Duplex stainless steel is developed on the basis of single-phase stainless steel, its Ni content is generally about half of austenitic stainless steel Ni content, reducing the alloy cost. Austenitic stainless steel has excellent corrosion resistance and high comprehensive performance, it solves the weakness of ferritic and martensitic stainless steel corrosion resistance, austenitic stainless steel strength and wear resistance. In the field of petroleum and petrochemical, it is mainly used in seawater corrosion resistant offshore oil platforms, acidic components and equipment, especially in pitting corrosion resistant components.
Precipitation strengthening stainless steel is mainly through precipitation strengthening mechanism to obtain high strength performance, it also sacrifices its own corrosion resistance, so it is less used in corrosive medium, generally used in petrochemical machinery mining and other industries.
Application of stainless steel tubing in petroleum and petrochemical industry
Petroleum and petrochemical industry is the pillar industry of the national economy, which plays an important role in the national economy. In the past 20 years, stainless steel pipe whether seamless pipe or welded pipe in the production technology level has been greatly improved. The stainless steel pipe produced by some domestic manufacturers has reached the level that can completely replace imported products, realizing the localization of steel pipe.
In petroleum and petrochemical industry, stainless steel pipe is mainly used in pipeline conveying system, including high-pressure furnace tube, piping, petroleum cracking pipe, fluid conveying pipe, heat exchange tube and so on. Stainless steel is required to perform well in wet and acid service.
Post time: Jun-20-2022