Definition - What does Alloy 2205 mean?
Alloy 2205 is an austenitic-ferric stainless alloy with high mechanical strength, excellent impact strength and an outstanding resistance to stress corrosion cracking, pitting and crevice corrosion. This makes it suitable for applications that demand high strength and good corrosion resistance.
The alloy 2205 is also referred to as Avesta Sheffield 2205, Grade 2205 Duplex or UNS 31803.
Corrosionpedia explains Alloy 2205
The alloy 2205 combines the benefits of ferritic and the austenitic steels, and has very high mechanical strength in addition to a very good uniform and pitting corrosion resistance to stress corrosion cracking.
The composition of the alloy includes:
- Chromium 22–23%
- Nickel 4.5–6.5%
- Molybdenum 3–3.5%
- Manganese 2.0 (max)
- Silicon 1.0%
- Nitrogen 0.14–0.20 %
- Iron takes the balance of about 50%
The high chromium, nitrogen and molybdenum contents enhance the resistance to corrosion in most environments. Furthermore, the alloying elements increase the resistance to pitting and crevice corrosion in strong acidic and oxidizing solutions. The alloy’s duplex microstructure enhances the resistance to stress corrosion cracking.
The annealing of the stainless steel should be carried out at a minimum temperature of 1900°F. This is then followed by rapid cooling by water quenching. The process is applicable to solution annealing as well as stress-relieving. Treating the alloy at lower temperatures will lead to precipitation of the inter-metallic or non-metallic phase, which can be detrimental.
The alloy 2205 characteristics are:
- High mechanical strength
- Outstanding resistance to corrosion cracking, erosion and fatigue
- High uniform resistance to pitting and crevice corrosion
- High resistance to sulfide stress corrosion cracking
- Higher heat conductivity, low thermal expansion and useful up to 600°F
Available forms include: sheet, plate, bar, tubular, pipe, wire, coil, forging, castings, etc.
The alloy has good weldability properties in which the weld metal and the heat-affected zone retain the strength, toughness and corrosion resistance of the base metal. However, care should be taken to ensure a favorable balance that avoids precipitation of the inter-metallic or non-metallic phases.
The alloy’s properties make it useful in applications and processing equipment subjected to both cycle load and aggressive corrosive environments. Typical applications include:
- Pressure vessels for chloride and other chemical processing and transport tanks
- Heat exchangers, pipes and tubes for the desalination and the oil & gas industries
- Piping and welding consumables for chemical tankers
- Acetic acid distillation components
- Pulp mill digesters