1. Low-temperature embrittlement performance of stainless steel pipes. In a low-temperature environment, the deformation energy is small. In a low temperature environment, the phenomenon that elongation and reduction of area decrease is called low temperature embrittlement. Mostly produced on the body-centered cubic structure of the ferrite series.
1. Low temperature embrittlement performance of stainless steel pipes-in a low temperature environment, the deformation energy is small. In a low temperature environment, the phenomenon that elongation and reduction of area decrease is called low temperature embrittlement. Mostly produced on the body-centered cubic structure of the ferrite series.
2. Low-temperature processing performance of stainless steel pipes-the martensitic stainless steel is quenched from austenitizing temperature and then cooled to a very low temperature to promote the quenching method of martensite. Suitable for easy production of retained austenite stainless steel.
At low temperatures, the resistance, linear expansion coefficient, thermal conductivity, mass melting and magnetism of stainless steel pipes will change greatly. Resistance and linear expansion coefficient decrease at low temperature; thermal conductivity and mass heat capacity decrease sharply at low temperature; Young's modulus (longitudinal elastic modulus) increases at the same time as the temperature drops. Since the austenitic stainless steel pipe has a low temperature (Subzreo temperature) Ms point (martensite transformation start temperature or martensite formation temperature), martensite can be formed when it is kept below the Ms point. The formation of martensite at low temperature makes SUS304 (18Cr-8Ni), the representative steel grade of austenitic stainless steel, non-magnetic at room temperature, but becomes magnetic at low temperature.
Regarding the low-temperature brittleness of ferritic stainless steel pipes like carbon steel, in the low-temperature state, austenitic steel does not exist. Therefore, ferritic or martensitic stainless steel produces low-temperature embrittlement, while austenitic stainless steel or nickel-based alloy does not show low-temperature embrittlement. Ferritic stainless steel pipes such as SUS410 (13Cr) and SUS430 (18Cr) show a sharp drop in impact value at low temperatures. Therefore, it is necessary to pay special attention when using it at low temperature. As a method to improve the impact toughness of ferritic stainless steels, a high-purification process can be considered. With the help of controlling C and N grade levels, when the embrittlement temperature is improved in the range of -50°C to -100°C, it is possible to use it in freezing-related engineering. In recent years, SUS430LX (18Cr-Ti, Nb-LC) and SUS436L (18Cr-Mo-Ti, Nb-LC) have been applied to the shells of refrigeration appliances.
Because the ferritic stainless steel has a body-centered cubic structure, when the material performance becomes weak, sharp cracks will rapidly expand and cause brittle failure. The austenitic series stainless steel will not produce brittle failure because of its face-centered cubic structure. Aoshu invested in stainless steel SUS304L (18Cr-9Ni-LC) and SUS316L (18Cr-12Ni-2Mo-LC), etc., showing superior impact characteristics at low temperatures. It should be noted that the precipitation of ferrite or martensite due to processing, and the tendency of embrittlement due to the precipitation of carbides or σ-equivalent phases due to sensitization.
