The material selection and application skills of cryogenic pipes can be summarized as follows:
First, the selection of materials
Austenitic stainless steels
This type of steel has a stable face-centered cubic lattice structure, which is mainly characterized by good toughness and low temperature resistance. There is no loss of toughness at low temperatures of -196°C, including varieties such as 304L and 316. Austenitic stainless steels can be used below -196°C and are suitable for liquefaction, storage and transportation of natural gas, as well as cryogenic equipment for liquid nitrogen.
Aluminum alloy
Aluminum alloy pipes have excellent low-temperature properties and good mechanical properties, high tensile strength and good corrosion resistance. It is used under low temperature conditions and is not easy to deform, brittle and age. In addition, it has good electrical conductivity and thermal insulation properties, which can ensure the temperature stability of the pipeline conveying medium.
Low-temperature high-strength steel
This kind of low-temperature pipeline is mainly made of carbon and manganese, and a small amount of nickel-chromium is added to improve the low-temperature toughness of the steel. At the same time, a small amount of molybdenum-vanadium components are added to improve the strength of the steel. This material has high strength and high temperature resistance, and is a strong and tough material, which can be used for various engineering spherical tanks and low-temperature pressure containers.
Nickel-based low-temperature steel
With nickel as the main element, the low-temperature toughness will also improve as the nickel content increases. This type of steel can be used in low-temperature equipment at -40~-196°C. For example, normalized 2.5% nickel steel can be used up to -50°C, and normalized 3.5% nickel steel can be used up to -88°C.
Second, application skills
Weldability and plastic deformation
At low temperatures, materials are prone to brittleness, so the welding process and joint design are particularly important. Reasonable welding process and joint design can effectively reduce the brittle tendency of the welding area and improve the overall reliability of the piping system. The high plastic deformation capacity can reduce the influence of thermal stress on the piping system and extend its service life.
Prevent leakage and volatilization of media
When selecting materials, it is necessary to ensure that the material itself has low permeability and high sealing performance to prevent leakage of low-temperature media. At the same time, the installation and connection of the pipeline system should adopt reliable seals and connections to ensure that the pipeline system can maintain good sealing performance under low temperature conditions.
Cost and sustainability
When selecting cryogenic piping materials, consider cost, sustainability, and performance over long-term use, maintenance and repair costs. With the increasing awareness of environmental protection, more and more attention is being paid to the sustainability of materials and the efficiency of resource use.
In summary, the material selection and application skills of cryogenic pipes need to comprehensively consider the low temperature resistance, welding performance and plastic deformation ability of the material, the ability to prevent media leakage and volatilization, as well as the cost and sustainability and other factors. Through reasonable selection and application, the safe, reliable and efficient operation of cryogenic piping systems can be ensured.
