2205 Duplex/Super Duplex Stainless Steel (1.4462,UNS S31803/UNS S32205)

2205 is a 22% Chromium, 3% Molybdenum, 5-6% Nickel nitrogen alloyed duplex stainless steel with high general, localized and stress corrosion resistance properties in addition to high strength and excellent impact toughness.
2205 provides pitting and crevice corrosion resistance superior to 316L or 317L austenitic stainless steels in almost all corrosive media. It also has high corrosion and erosion fatigue properties as well as lower thermal expansion and higher thermal conductivity than austenitic.
The yield strength is about twice that of austenitic stainless steels. This allows a designer to save weight and makes the alloy more cost competitive when compared to 316L or 317L.
2205 is particularly suitable for applications covering the -50F/+600F temperature range. Temperatures outside this range may be considered but need some restrictions, particularly for welded structures.

Chemical Analysis:
Typical values (Weight %)
C Cr Ni Mo N Others
0.020 22.1 5.6 3.1 0.18 S=0.001

Standards:
ASTM/ASME...........A240 UNS S32205/S31803
EURONORM...........1.4462 X2CrNiMoN 22.5.3
AFNOR...................Z3 CrNi 22.05 AZ
DIN.........................W. Nr 1.4462

Corrosion Resistance:
--General Corrosion
Because of its high chromium (22%), molybdenum (3%), and nitrogen (0.18%) contents, the corrosion resistance properties of 2205 are superior to that of 316L or 317L in most environments.
--Stress Corrosion Resistance
The duplex microstructure is known to improve the stress corrosion cracking resistance of stainless steels.
Chloride stress corrosion cracking of austenitic stainless steels can occur when the necessary conditions of temperature, tensile stress, oxygen, and chlorides are present. Since these conditions are not easily controlled, stress corrosion cracking has often been a barrier to utilizing 304L, 316L, or 317L.
--Corrosion Fatigue Resistence
2205 combines high strength and high corrosion resistance to produce high corrosion fatigue strength. Applications in which processing equipment is subject to both an aggresively corrosive enviroment and to cycle loading can benefit from the properties of 2205.

Hot Forming:
Forming below 600F is recommended whenever possible. When hot forming is required, the workpiece should be heated uniformly and worked in the range of 1750 to 2250F. 2205 is quite soft at these temperatures and is readily formed. Above this range, 2205 is subject to hot tearing. Below 1700F there can be rapid formation of intermetallic phases because of the combination of temperature and deformation. Whenever hot forming is done, it should be followed by a full solution anneal at 1900F minimum and rapid quench to restore phase balance, toughness, and corrosion resistance. Stress relieving is not required or recommended; however, if it must be performed, the material should receive a full solution anneal at 1900F minimum, followed by rapid cooling or water quenching.

Cold Forming:
2205 is readily sheared and cold formed on equipment suited to working stainless steels. However, because of the high strength and rapid work hardening of 2205, forces substantially higher than those for austenitic steels are required to cold form 2205. Also because of the high strength, a somewhat larger allowance must be made for springback.

Heat Treatment:
2205 should be annealed at 1900F minimum, followed by rapid cooling, ideally by water quenching. This treatment applies to both solution annealing and stress relieving. Stress relief treatments at any lower temperature carry the risk of precipitation of detrimental intermetallic or nonmetallic phases.

Machinability:
With high-speed steel tooling, 2205 may be machined at the same feeds and speeds as Alloy 316L. When carbide tooling is used, cutting speeds should be reduced by about 20% relative to the speeds for Alloy 316L. Powerful machines and rigid mounting of tools and parts are essential.

Welding:
2205 possesses good weldability. The goal of welding 2205 is that the weld metal and heat-affected zone (HAZ) retain the corrosion resistance, strength, and toughness of the base metal. The welding of 2205 is not difficult, but it is necessary to design welding procedures that lead to a favorable phase balance after welding and will avoid precipitation of detrimental intermetallic or nonmetallic phases.
2205 can be welded by: GTAW (TIG); GMAW (MIG); SMAW ("stick" electrode); SAW; FCW; and PAW.

Applications:
Pressure vessels, tanks, piping, and heat exchangers in the chemical processing industry
Piping, tubing, and heat exchangers for the handling of gas and oil
Effluent scrubbing systems
Pulp and paper industry digesters, bleaching equipment, and stock-handling systems
Rotors, fans, shafts, and press rolls requiring combined strength and corrosion resistance
Cargo tanks for ships and trucks
Food processing equipment
Biofuels plants