We all know that the organizational structure of austenitic non-magnetic stainless steel pipes, demagnetized stainless steel pipes, and demagnetized stainless steel pipes is austenite. Due to the characteristics of austenitic stainless steel, it has good low-temperature toughness, and at the same time, its plasticity and toughness at low temperatures. are all good. Therefore, austenite has become one of the main materials for manufacturing cryogenic unit operating equipment in cryogenic storage and transportation equipment. So, what is the low-temperature performance of austenitic thin-walled stainless steel pipes?
1. Mechanical properties: At low temperatures, the tensile strength and yield strength of demagnetized stainless steel pipes (stainless steel degaussing pipes) will increase as the temperature decreases. Among them, the tensile strength is more sensitive to temperature and the increase is more significant.
2. Physical properties: At low temperatures, the thermal conductivity and specific heat capacity of austenite decrease as the temperature decreases, making it easy for low-temperature storage and transportation equipment made of demagnetized stainless steel tubes (stainless steel degaussing tubes) to reduce heat loss to a minimum. The decrease in temperature will increase the thermal expansion coefficient of austenitic steel. Therefore, when selecting welding materials for low-temperature materials, we should choose welding materials with a thermal expansion coefficient similar to that of the base metal.
3. The crystal structure of the metal itself: Demagnetized stainless steel tubes (stainless steel demagnetized tubes) belong to a face-centered cubic lattice. This crystal structure has strong toughness at low temperatures and will not embrittle to a large extent.
4. Chemical composition: The main chemical elements of demagnetized stainless steel tubes (stainless steel degaussed tubes) include carbon, chromium, nickel, manganese, niobium, etc. Chromium can form a dense oxide film on the surface of the pipe, and the addition of nickel can make austenitic steel obtain strong corrosion resistance and excellent low-temperature performance. When selecting materials for cryogenic storage tanks, we must focus on low-temperature performance and corrosion resistance, so we must choose from low-carbon or ultra-low-carbon stainless steel. The carbon content of 304L and 316L materials is only 0.03%.
5. Martensite begins to transform temperature: If austenite is not treated properly, it will transform into martensite, thereby greatly reducing the toughness of demagnetized stainless steel pipes (stainless steel demagnetized pipes). The reason why 304L and 316L stainless steel in austenite are used as low-temperature materials is that their martensite starts to transform at around -200°C.
The above is the low-temperature performance of a demagnetized stainless steel tube (stainless steel demagnetized tube). In low-temperature environments, the tensile strength and yield strength of austenitic thin-walled pipes will increase as the temperature decreases; the thermal conductivity and specific heat capacity of steel pipes decrease as the temperature decreases; the austenite structure has stronger toughness, and there will not be a large degree of embrittlement; for thin walls working in low-temperature environments, it is recommended to use 304L and 316L materials.
Post time: Feb-23-2024