At the end of the 20th century, stainless steel "super" grades were produced at home and abroad. Different literatures have different definitions of super-stainless steel. Some literatures suggest that high-performance stainless steel is also called super-stainless steel; some literatures believe that high-alloy stainless steel is called super-stainless steel; some literatures believe that super-stainless steel also includes high-performance, Special requirements for some low-alloy stainless steels, such as super 304H chrome-nickel austenitic stainless steel; some literatures believe that super-stainless steel refers to pitting resistance equivalent PREN value ≥ 35 (ferritic stainless steel) or ≥ 40 (austen High-alloyed high-performance stainless steel in stainless steel and duplex stainless steel; some literatures further believe that super-stainless steel should also include ultra-high cleanliness, ultra-high uniformity, ultra-fine structure, ultra-high surface quality, and excellent resistance to harsh media. Local corrosion performance, good process manufacturing performance and so on.
2. Common characteristics of super stainless steel
■ It has a finer special component design than the four types of stainless steel;
■ It has a high degree of clarity;
■ Excellent uniformity (ingredients, organization and properties);
■ It has better performance than the four types of stainless steel in harsh environments;
■ Has good process manufacturing performance;
■ It has a high cost performance;
3. Definition of super stainless steel
■ Super stainless steel is a type of stainless steel, one of the iron-based alloys with a Cr content of 12-30%.
Super stainless steel must contain more than 12% Cr, but the Cr content is usually ≤ 30%;
■ Super stainless steel is not an iron-nickel-based corrosion-resistant alloy, because the content of Ni in iron-nickel-based corrosion-resistant alloys is >30%.
Ni + Fe ≥ 50%; so for Ni-containing super stainless steel, the amount of Ni must be ≤ 30%;
■ Super stainless steel must have better performance in harsh environments, such as local corrosion resistance such as pitting corrosion
It can be characterized by pitting resistance equivalent PREN=%Cr+3.3(%Mo)+16(%N). Usually super austenitic stainless steel
The PREN of super duplex stainless steel should be ≥40, and the PREN of super ferritic stainless steel should be ≥35.
Super stainless steel for special use requirements must have an abnormal breakthrough in the weak link of key performance.
For example, super martensitic stainless steel must be weldable "soft martensitic stainless steel"; super high temperature austenite is not
Stainless steel must break through the creep problem of 600 ° C or more and 300 bar stress.