Super Austenitic Stainless Steels
Introduction
The super austenitic stainless steels were developed to provide alloys with better resistance to localized corrosion, which is one of the important directions of the development of high quality special stainless steel. A super austenitic stainless steel is considered to be one with a Pitting Resistance Equivalent Number (PREN) greater than 40. Compared with ordinary austenitic stainless steel, super austenitic stainless steel has higher element content of Cr, Ni, Mo, N, etc. Super austenitic stainless steel is favored for its advantages of super corrosion resistance, excellent comprehensive mechanical properties and relatively low cost and has become one of the most economical and applicable key materials in the high-end equipment manufacturing industry related to energy conservation and environmental protection, ocean engineering, petrochemical and other key fields.
Development & Property & Application
- The development of super austenitic stainless steel has gone through three stages. In the 1930s, to solve the problem of poor corrosion resistance of ordinary austenitic stainless steel in sulfuric acid medium, 904L with 4.5% Mo and 20# with 2.5% Mo were developed. In the 1970s, to solve the serious corrosion problems in flue gas desulphurization units and chlorine-containing equipment, AL-6X alloy was developed. After the 1980s, it was found that a certain amount of Mn combined with higher Cr and Mo could further improve the N solubility based on theoretical calculation and other means, then the 654SMO containing 7% Mo was developed.
- Super austenitic stainless steel has the following characteristics: (1) Excellent uniform corrosion resistance: the uniform corrosion resistance of super austenitic stainless steel is much higher than that of traditional stainless steel; (2) Excellent pitting corrosion resistance and crevice corrosion resistance: both pitting corrosion and crevice corrosion can cause a high degree of local corrosion of materials in a short time, and the combined action of Cr, Mo and N elements in super austenitic stainless steel makes they have excellent local corrosion resistance. (3) Strong comprehensive mechanical properties: super austenitic stainless steel shows significantly greater mechanical properties than traditional stainless steel. Its strength, toughness and yield strength are 50%-100% higher than ordinary austenitic stainless steel. Some alloys even have better mechanical properties than nickel alloys of Inconel 625 and C-276.
- Due to very excellent pitting corrosion resistance and crevice corrosion resistance in the extreme harsh environment such as halide and good comprehensive mechanical properties, super austenitic stainless steel, as a ideal replacement material for nickel-based alloy and titanium alloy, can be widely used in extremely demanding environment such as energy conservation and environmental protection (flue gas desulfurization, waste incineration), marine engineering (seawater desalination, desalination industry), petrochemical industry (offshore oil platforms, oil refining units), chemical industry (phosphorus acid, fertilizer, pharmaceutical), paper industry and other fields.
As a leading supplier of metals and alloys, Alfa Chemistry now can provide various super austenitic stainless steels in the shapes of bar, wire, strip, foil, pipe, tube, sheet, plate, forgings, pipe fittings, flanges, etc. The main products include: