Low temperature embrittlement of stainless steel pipe --- in low temperature environment, the deformation energy is small. In the low temperature environment, the phenomenon that the elongation and area shrinkage decrease is called low temperature embrittlement. Most of them are produced on the body centered cubic structure of ferrite series. 1. Low temperature embrittlement of stainless steel pipe --- in low temperature environment, the deformation energy is small. In the low temperature environment, the phenomenon that the elongation and area shrinkage decrease is called low temperature embrittlement. Most of them are produced on the body centered cubic structure of ferrite series.
2. Low temperature processing of stainless steel pipe --- quenching martensitic stainless steel from austenitizing temperature and then cooling to very low temperature to promote the quenching method of producing martensite. It is suitable for stainless steel which is easy to produce retained austenite.
The resistance, coefficient of linear expansion, thermal conductivity, quality, hot melt and magnetism of stainless steel pipe will change greatly at low temperature. Resistance, linear expansion coefficient decreases at low temperature; The thermal conductivity and mass heat capacity decrease sharply at low temperature; Young's modulus (longitudinal elastic modulus) increases at the same time when the temperature decreases. Because the austenitic series stainless steel pipe has MS point (martensite transformation start temperature or martensite formation temperature) at low temperature (subzreo temperature), martensite can be formed when it is kept below MS point. The formation of martensite at low temperature makes the representative steel SUS304 (18Cr-8Ni) of austenitic series stainless steel non-magnetic at room temperature and magnetic at low temperature.
At low temperature, ferritic stainless steel pipe has low-temperature brittleness like carbon steel, but austenitic steel does not. Therefore, ferritic or martensitic stainless steel produces low-temperature brittleness, while austenitic stainless steel or nickel base alloy does not show low-temperature brittleness. Sus410 (13Cr) and SUS430 of ferritic stainless steel pipe (18cr) etc. show a sharp drop in impact value at low temperature. Therefore, it is necessary to pay special attention when using at low temperature. As a method to improve the impact toughness of ferritic series stainless steel, high purification process can be considered. When the embrittlement temperature is improved in the range of - 50 ℃ to - 100 ℃ by controlling the level of C and N, it is possible to use it in freezing phase In recent years, sus430lx (18cr Ti, Nb LC) and sus436l (18cr Mo Ti, Nb LC) have been
Ferritic stainless steel is a body centered cubic structure. When the material properties become weak, sharp cracks will expand rapidly and cause brittle failure. Austenitic series stainless steel will not produce brittle failure because it is a face centered cubic structure. Austrian stainless steel SUS304L (18cr-9ni-lc) and SUS316L are used (18cr-12ni-2mo-lc) shows that it still has superior impact characteristics at low temperature. However, pay attention to the precipitation of ferrite or martensite due to processing, as well as carbide or carbide due to sensitization σ The tendency of embrittlement caused by equal heterogeneous precipitation.