First, the low temperature embrittlement performance of stainless steel pipe in a low temperature environment, the deformation energy is small. In low temperature environment, the phenomenon that elongation and section shrinkage decrease is called low temperature embrittlement. It is mostly produced in the body centered cubic structure of the ferrite series. Two, stainless steel pipe low temperature processing
First, low temperature embrittlement performance of stainless steel pipe - in a low temperature environment, the deformation energy is small. In low temperature environment, the phenomenon that elongation and section shrinkage decrease is called low temperature embrittlement. It is mostly produced in the body centered cubic structure of the ferrite series.
Second, low temperature processing performance of stainless steel pipe - the martensitic system of stainless steel from austenitizing temperature quenching and then cooling to very low temperature to promote the production of martensite quenching method. Suitable for stainless steels that are easy to produce residual austenite.
At low temperatures, the resistance, coefficient of linear expansion, thermal conductivity, mass hot melt and magnetic properties 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 tube has a low temperature (Subzreo temperature) Ms point (martensitic transformation start temperature or martensitic formation temperature), martensitic can be formed when it is kept below the Ms point. The formation of martensite at low temperature makes the representative steel SUS304 (18Cr-8Ni) of Austenitic system stainless steel non-magnetic at room temperature, and becomes magnetic at low temperature.
At low temperatures, ferritic stainless steel pipes have low temperature brittleness like carbon steel, while austenitic steel does not. Therefore, ferritic or martensitic stainless steels produce low temperature embrittlement while Austenitic stainless steels or nickel-based alloys do not. SUS410 (13Cr), SUS430 (18Cr) and other ferritic stainless steel pipes show a sharp drop in impact value at low temperature. Therefore, when used at low temperatures, it is necessary to pay special attention. As a method to improve the impact toughness of ferritic series stainless steel, high purification process can be considered. By controlling C, N class levels, it is possible to use it for refrigeration-related engineering when the embrittlement temperature is improved in the range of -50 ° C to -100 ° C. In recent years, SUS430LX (18Cr-Ti,Nb-LC) and SUS436L (18Cr-Mo-Ti,Nb-LC) have been applied to the housing of refrigerating appliances.
Because the ferritic stainless steel is a body-centered cubic structure, when the material properties are weak, sharp cracks will rapidly expand and cause brittle damage. Austenitic stainless steel is not brittle because of its face-centered cubic structure. Archo-invested stainless steel SUS304L (18Cr-9Ni-LC) and SUS316L (18Cr-12Ni-2Mo-LC) have shown that they still have superior impact characteristics at low temperatures. It should be noted that the precipitation of ferrite or martensite caused by processing, and the tendency of embrittlement caused by the precipitation of carbide or σ-equal phase due to sensitization.
