926 Super Austenitic Stainless Steel (UNS N08926)

926 Super Austenitic Stainless Steel (UNS N08926)

Super stainless steel is a special stainless steel with a different chemical composition than conventional stainless steel. It is a high-nickel, high-chromium, and high-molybdenum high-alloy stainless steel. Super stainless steel is classified into numerous varieties based on the microstructure properties of stainless steel materials, including super ferritic stainless steel, super austenitic stainless steel, super martensitic stainless steel, and super duplex stainless steel. Super austenitic stainless steel improves on ordinary austenitic stainless steel by increasing alloy purity, increasing the number of beneficial elements, decreasing C content, preventing intergranular corrosion caused by Cr23C6 precipitation, obtaining good mechanical properties, process properties, and local corrosion resistance, and replacing Ti-stabilized stainless steel.

Alloy 926 is a super austenitic stainless steel, a nickel-based alloy containing titanium and aluminum, containing 14%–18% Cr and 24%–26% Ni, and containing enough chromium to form and maintain sufficient chromium oxides to protect it under high-temperature conditions, making it more resistant to high temperatures than traditional chromium-nickel stainless steels such as 304; the higher nickel content gives it better oxidation resistance compared to standard 18–8 stainless steel.

926 super austenitic stainless steel is based on the 904L alloy, which has very high resistance to pitting and crevice corrosion in halide media and acidic environments containing sulfur and hydrogen and can effectively resist chloride ion stress corrosion; it also has good corrosion resistance in oxidizing and reducing media, with good stability and slightly better mechanical properties than 904L, and can be used in the manufacture of pressure vessels from 926 super austenitic stainless steel.

Chemical Composition (%) of 926 Super Austenitic Stainless Steel (UNS N08926)

Mechanical Properties of 926 Super Austenitic Stainless Steel (UNS N08926)

Physical Properties of 926 Super Austenitic Stainless Steel (UNS N08926)

Corrosion Resistance of 926 Super Austenitic Stainless Steel (UNS N08926)

Alloy 926 is an austenitic stainless steel with a chemical composition comparable to Alloy 904L but with a higher nitrogen percentage of about 0.2% and a molybdenum content of about 6.5%. The enhanced nitrogen and molybdenum concentrations greatly increase the resistance of halide media to pitting and crevice corrosion. At the same time, nickel and nitrogen not only assure the stability of the metallographic phase but also limit the likelihood of intergranular phase precipitation during hot working or welding. Alloy 926 is highly resistant in chloride-ion conditions because of its good localized corrosion resistance and 25% nickel content. In addition to sulfuric acid, phosphoric acid, acidic gases, seawater, salts, and organic acids, Alloy 926 possesses outstanding corrosion resistance in other chemical media as well as in high-temperature, highly concentrated media.

Heat processing of 926 Super Austenitic Stainless Steel (UNS N08926)

- Alloy 926 has a hot operating temperature range of 1200°C to 900°C. Water quenching or quick air cooling is used for cooling.
- When heated, the material is fed directly into a furnace that has been preheated to the maximum working temperature, and after being held for a sufficient amount of time (60 minutes of holding time per 100 mm of thickness is required), it is quickly discharged from the furnace and hot worked in the high-temperature section of the specified temperature range. Reheating is required when the material temperature falls below the hot operating temperature.
- After hot working, solid solution treatment is performed to achieve the best performance.

Cold Processing of 926 Super Austenitic Stainless Steel (UNS N08926)

- Alloy 926, like all austenitic chromium-nickel stainless steels, has a high rate of work hardening and hence necessitates the selection of processing equipment. Cold worked material should be solution heat treated and intermediate annealed for larger cold worked volumes.
- If the cold working volume is greater than 15%, the workpiece must be treated with a secondary solution.

Heat Treatment of 926 Super Austenitic Stainless Steel (UNS N08926)

- The temperature range for solid solution treatment of alloy 926 is 1150°C to 1200°C, with 1170°C being the most suitable.
- Water quenching is utilized for materials with a thickness larger than 1.5 mm, and quick air cooling can be used for materials with a thickness less than 1.5 mm.
- If air cooling is employed, the material can be fed directly into the furnace, which has been preheated to the highest working temperature throughout the heat treatment process, and the workpiece must be kept clean.

Features of 926 Super Austenitic Stainless Steel (UNS N08926)

- Excellent resistance to pitting and crevice corrosion
- Excellent chloride ion stress corrosion resistance
- Good stability
- Good mechanical properties
- Good resistance to high temperature
- Excellent wear resistance
- Good oxidation resistance
- Good hot and cold workability

Applications of 926 Super Austenitic Stainless Steel (UNS N08926)

926 super austenitic stainless steel is mainly used in chemical, paper, marine, aerospace, and power industries.
- Heat exchangers
- Corrosive chemical transport storage tanks
- Seawater desalination equipment
- Flue gas desulfurization equipment
- Radiator components
- Sulfuric acid conveying device
- Seawater filtration system
- Pulp drifting system

Equivalent Grades of 926 Super Austenitic Stainless Steel (UNS N08926)