Introduction to mechanical and physical properties of super austenitic stainless steel

The metallographic structure of super austenitic stainless steel belongs to the typical complete austenitic structure. However, because the content of chromium and molybdenum is relatively high, it is very likely that a metal interphase will be produced. These metallic mesophases often appear in the center of the stainless steel sheet. However, after proper heat treatment, the formation of these metallic intermediate phases can be effectively prevented, resulting in a nearly complete austenitic structure. The microstructure of Avesta Sheffield 254 SMO super austenitic stainless steel is free of any other metallic interphases. The organization is obtained after heat treatment at a temperature of 1150-12000C.

During use, if a small amount of metal intermediate phases appear, these phases will also excessively affect the mechanical properties and surface corrosion resistance of super austenitic stainless steel. However, it is still necessary to prevent the temperature range from reaching 600-1000°C as much as possible, especially when welding and hot working.
Regarding mechanical properties, the austenitic structure usually has better strength and forgeability. After adding a certain amount of nitrogen, in addition to enhancing the corrosion resistance of the material, while maintaining the forgeability and toughness of the austenitic stainless steel, the high-nitrogen super austenitic stainless steel will also have very strong mechanical strength. Its yield strength is 50-100% higher than ordinary austenitic stainless steel.
Mechanical strength increases with nitrogen content at all temperatures. Although the strength has been greatly improved, the elongation of super austenitic stainless steel is still high. Even higher than the elongation of many low alloy steels. This is mainly due to its high nitrogen content and another characteristic associated with it, namely high work hardening rate.
Therefore, the cold-formed parts can obtain high strength. Applications that can take advantage of this feature include pipes and bolts in deeper wells. Like ordinary austenitic stainless steel, the low temperature performance of super austenitic stainless steel is also very good. The impact resistance and fracture resistance of super austenitic stainless steel are very high, and it will only decrease slightly when it is as low as -196 °C.
Regarding the physical properties, this is mainly influenced by the austenitic structure, but also partly depends on the chemical composition of the super austenitic stainless steel. That is, super austenitic stainless steel has little difference in physical properties compared with ordinary austenitic stainless steel, such as 304 or 316 stainless steel.