The 2205 alloy ( UNS S32305/S31803 ) is a duplex stainless steel consisting of 22% chromium, 3% molybdenum and 5-6% nickel-nitrogen alloy. It has high strength, good impact toughness and good overall and local resistance to strong corrosion. Compared with 316L and 317L austenitic stainless steels, 2205 alloy has superior corrosion resistance and crack resistance. It has high corrosion resistance and its thermal expansion coefficient is lower than that of austenite. More sexual. Compared with austenitic stainless steel, it has twice the compressive strength. Compared with 316L and 317L, the designer can reduce its weight and the cost is lower.
This alloy is particularly suitable for use in the temperature range of -50F/+600F, and can be used for lower temperatures under severe restrictions (especially for welded structures).
Applications • Pressure vessels, high pressure storage tanks, high pressure piping, heat exchangers (chemical processing industry).
• Oil and gas pipelines, heat exchanger fittings.
• Sewage treatment system.
• Pulp and paper industry classifiers, bleaching equipment, storage handling systems.
• Rotary shafts, press rolls, blades, impellers, etc. in high-strength, corrosion-resistant environments.
• Cargo box for a ship or truck
• Food processing equipmentCorrosion resistance Generally, corrosion resistance is due to its high chromium, molybdenum and nitrogen content. The corrosion resistance of 2205 is better than that of 316L and 317L in most environments. The content of chromium, molybdenum and nitrogen in 2205 makes it corroded. Sexual and acidic solutions have strong resistance to rust and crevice corrosion.
Corrosion curve 4 mpy (0.1 mm/yr) in a sulfuric acid solution containing 2000 ppm of chloride
The complex microstructure of the stress corrosion resistant stainless steel helps to improve its resistance to stress crevice corrosion.
Chloride stress corrosion can occur in the presence of certain temperatures, pressures, oxygen and chlorides. Because these conditions are not suitable for control. The use of 304L, 316L and 317L is limited in this respect.
Anti-fatigue strength corrosion
The high strength and corrosion resistance of 2205 alloy gives it a high resistance to corrosion and fatigue. Mainly used in environments with strong corrosiveness.The critical temperature of erosion in 1 M NaCl was measured using an AvestaPolarit etched cell.
Critical temperature of crack corrosion in 10% FeCl3•6H2O
General corrosion in wet treated phosphoric acid
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Corrosion rate , ipy
grade
Solution A, 140F
Solution B, 120F
2205
3.1
3.9
316L
>200
>200
904L
47
6.3
Ingredients , wt %
P 2 O 5
HCl
HF
H 2 SO 4
Fe 2 O 3
Sol A 54.0
0.06
1.1
4.1
0.27
Sol B 27.5
0.34
1.3
1.72
0.4
Ingredients , wt %
P 2 O 5
Al 2 O
SiO 2
CaO
MgO
Sol A 54.0
0.17
0.10
0.20
0.70
Sol B 27.5
0.01
0.3
0.02
--
Stress cracking resistance
grade
Boiling 42% MgCI 2
Wick Test
Boiling 25% NaCI
2205
F
P
P
254 SMO®
F
P
P
Type 316L
F
F
F
Type 317L
F
F
F
Alloy 904L
F
F or P
F or P
Alloy 20
F
P
P
(p=pass F=not passed)
chemical composition
C
Cr
Ni
Mo
N
Others
0.020
22.1
5.6
3.1
0.18
S=0.001
PREN = [Cr%] = 3.3 [Mo%] = 16 [N%] ≥ 34
Mechanical properties Mechanical properties at room temperature
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ASTM A 240
Typical
Yield strength (0.2%), ksi
65 min.
74
Compressive strength , ksi
90 min.
105
Extension rate , %
25 min.
30
Hardness HB
293 max.
256
Mechanical properties at high temperatures
Temperature ?F
122
212
392
572
Yield strength (0.2%), ksi
60
52
45
41
Compressive strength , ksi
96
90
83
81
Physical characteristics
Temperature F
Â
68
212
392
572
density
Lb/in 3
0.278
--
--
--
Elastic Modulus
Psi x 10 6
27.6
26.1
25.4
24.9
Line expansion (68? FT)
10 -6 /°F
--
7.5
7.8
8.1
Thermal Conductivity
Btu/h ft. °F
8.7
9.2
9.8
10.4
Heat capacity
Btu/lb/°F
0.112
0.119
0.127
0.134
Resistivity
In x 10 -6
33.5
35.4
37.4
39.4
structure
The chemical composition of 2205 is 50 α / 50 γ after the solid solution annealing treatment of 1040/1080C. If the heat treatment temperature is higher than 2000F, it may cause an increase in ferrite composition.
Like other duplex stainless steels, 2205 alloys are susceptible to precipitation from intermetallic phases. Intermetallic phase at 1300F and 1800F
Precipitated between them, the precipitation rate is the fastest at 1600F. Therefore, we need to test 2205, the test refers to ASTM A 923.Processing <br>Hot Forming We recommend that the forming should be carried out at temperatures below 600 °F. During the thermoforming process, the entire workpiece should be heated as a whole and should be carried out at temperatures ranging from 1750F to 2250F. The 2205 alloy is very soft at this temperature. If the temperature is too high, the 2205 alloy is prone to thermal tearing. If it is below this temperature, the austenite will break. Below 1700 °F, the intermetallic phase will form rapidly due to temperature and deformation. After the hot forming is completed, it should be subjected to solution annealing at a temperature of at least 1900F and quenched to reduce its phase balance, toughness and corrosion resistance. We do not recommend stress relief, but if this is necessary, the material should be solid solution annealed at a minimum temperature of 1900F and then rapidly cooled for water quenching.
Cold Formed 2205 alloy can be cut and cold formed. However, due to the high strength and hardness of the 2205 alloy itself, it requires more cold forming than austenitic steel, and because of its high strength, it is necessary to fully consider the rebound factor.
Heat treatment
The 2205 alloy should be annealed at a minimum temperature of 1900F and then rapidly cooled for water quenching. This treatment is applied to solution annealing and stress relief. Stress relief treatment, such as at temperatures below 1900 F, tends to result in the precipitation of harmful metal or non-metal phases.
Mechanical Machinability On high-speed machines, the feed rate and cutting speed of the 2205 alloy are the same as the 316L. If a carbonized knife is used, the cutting speed is reduced by approximately 20% compared to 316L, and the performance of the machine and its components plays a key role here.
welding
The 2205 alloy has good weldability. The properties to be achieved with the 2205 alloy are that the weld metal and the hot metamorphic portion retain the same corrosion resistance, strength and toughness as the base metal. Welding of 2205 is not difficult, but the welding procedure needs to be designed so that after welding, a good phase balance can be maintained to avoid the precipitation of harmful metal phases or non-metallic phases. 2205 can be soldered in the following equipment: GTAW (TIG); GMAW (MIG); SMAW ("stick" electrode); SAW; FCW; and PAW.
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