General
Properties
Alloy 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.
Alloy 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.
Alloy 2205 is particularly suitable
for applications covering the -50°F/+600°F
temperature range. Temperatures outside this range
may be considered but need some restrictions,
particularly for welded structures.
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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
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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
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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.
Localized Corrosion Resistance
The chromium, molybdenum, and nitrogen in 2205
also provide excellent resistance to pitting and
crevice corrosion even in very oxidizing and acidic
solutions.
Isocorrosion Curves 4 mpy (0.1 mm/yr), in sulfuric
acid solution containing 2000 ppm
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
Alloy 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.
Critical Pitting Temperature in 1M NaCl Measured
Using the AvestaPolarit Pitting Cell
Critical Crevice Corrosion Temperature (CCT)
in 10% FeCl3•6H2O
General Corrosion in Wet Process
Phosphoric Acids
| |
Corrosion
Rate, ipy |
| Grade |
Solution
A, 1401/4F |
Solution
B, 1201/4F |
| 2205 |
3.1 |
3.9 |
| 316L |
>200 |
>200 |
| 904L |
47 |
6.3 |
| Composition,
wt% |
| P2O5 |
HCl |
HF |
H2SO4 |
Fe2O3 |
| Sol A 54.0 |
0.06 |
1.1 |
4.1 |
0.27 |
| Sol B 27.5 |
0.34 |
1.3 |
1.72 |
0.4 |
| Composition,
wt% |
| P2O5 |
Al2O |
SiO2 |
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 Corrosion Cracking Resistance
| Grade |
Boiling 42% MgCI2 |
Wick Test |
Boiling 25% NaCI |
| 2205 |
F |
P |
P |
| 254 SMO® |
F |
P |
P |
| Alloy 316L |
F |
F |
F |
| Alloy 317L |
F |
F |
F |
| Alloy 904L |
F |
F or P |
F or P |
| Alloy 20 |
F |
P |
P |
(P=Pass, F=Fail)
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Chemical
Analysis
Typical values (Weight %)
| 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 |
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Mechanical
Properties
Mechanical Properties at Room Temperature
| |
ASTM A 240 |
Typical |
Yield
Strength 0.2%, ksi |
65 min. |
74 |
Tensile Strength,
ksi |
90 min. |
105 |
Elongation
% |
25 min. |
30 |
Hardness HB |
293 max. |
256 |
Tensile Properties at Elevated
Temperatures
| Temperature
°F |
122 |
212 |
392 |
572 |
| Yield Strength
(0.2%), ksi |
60 |
52 |
45 |
41 |
| Tensile
Strength, ksi |
96 |
90 |
83 |
81 |
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Physical Properties
| Temperature
°F |
|
68 |
212 |
392 |
572 |
| Density |
lb/in3 |
0.278 |
-- |
-- |
-- |
| Modulus of Elasticity |
psi x 106 |
27.6 |
26.1 |
25.4 |
24.9 |
| Linear Expansion
(681T4F-T) |
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 |
| Electrical
Resistivity |
in x 10-6 |
33.5 |
35.4 |
37.4 |
39.4 |
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Structure
The chemical analysis of 2205 is optimized
to obtain a typical 50 a/
50 g microstructure
after solution annealing treatment at 1900°/1922°F
(1040°/1080°C).
Heat treatments performed above
2000°F may result in an increase of ferrite
content.
Like all duplex stainless steels,
2205 is susceptible to precipitation of intermetallic
phases, usually referred to as sigma phase. Intermetallic
phases precipitate in the range of 1300°F
to 1800°F, with the most rapid precipitation
occurring at about 1600°F. Thus, it is prudent
to have 2205 pass a test for the absence of intermetallic
phases, such as those in ASTM A 923.
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Processing
Hot Forming
Forming below 600°F is recommended whenever
possible. When hot forming is required, the workpiece
should be heated uniformly and worked in the range
of 1750 to 2250°F. Alloy 2205 is quite soft
at these temperatures and is readily formed. Above
this range, 2205 is subject to hot tearing. Immediately
below this range, the austenite becomes substantially
stronger than the ferrite and may cause cracking,
a particular danger to “cold” edges.
Below 1700°F 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 1900°F 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 1900°F minimum, followed by rapid cooling
or water quenching.
Cold Forming
Alloy 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
Alloy 2205 should be annealed at 1900°F 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.
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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.
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Welding
Alloy 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.
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