Duplex 2205 stainless steel (both ferritic and austenitic) is used
extensively in applications that require good corrosion resistance
and strength. The S31803 grade stainless steel has undergone a
number of modifications resulting in UNS S32205, and was endorsed
in the year 1996. This grade offers higher resistance to corrosion.
At temperatures above 300°C, the brittle micro-constituents of this
grade undergo precipitation, and at temperatures below -50°C the
micro-constituents undergo ductile-to-brittle transition; hence
this grade of stainless steel is not suitable for use at these
temperatures.
Key Properties
The properties that are mentioned in the below tables pertain to
flat rolled products such as plates, sheets and coils of the ASTM
A240 or A240M. These may not be uniform across other products such
as bars and pipes.
Composition
Composition ranges for 2205 grade stainless steels
| Grade | | C | Mn | Si | P | S | Cr | Mo | Ni | N |
| 2205 (S31803) | Min Max | - 0.030 | - 2.00 | - 1.00 | - 0.030 | - 0.020 | 21.0 23.0 | 2.5 3.5 | 4.5 6.5 | 0.08 0.20 |
| 2205 (S32205) | Min Max | - 0.030 | - 2.00 | - 1.00 | - 0.030 | - 0.020 | 22.0 23.0 | 3.0 3.5 | 4.5 6.5 | 0.14 0.20 |
Mechanical Properties
Mechanical properties of 2205 grade stainless steels
| Grade | Tensile Str
(MPa) min | Yield Strength
0.2% Proof
(MPa) min | Elongation
(% in 50mm) min | Hardness |
| Rockwell C (HR C) | Brinell (HB) |
| 2205 | 621 | 448 | 25 | 31 max | 293 max |
Physical properties of 2205 grade stainless steels
| Grade | Density
(kg/m3) | Elastic
Modulus (GPa) | Mean Co-eff of Thermal
Expansion (μm/m/°C) | Thermal
Conductivity (W/m.K) | Specific
Heat
0-100°C ( J/kg.K) | Electrical
Resistivity
(nΩ.m) |
| 0-100°C | 0-315°C | 0-538°C | at 100°C | at 500°C |
| 2205 | 7800 | 190 | 13.7 | 14.2 | - | 19 | - | 418 | 850 |
Grade Specification Comparison
Grade specification comparisons for 2205 grade stainless steels
| Grade | UNS
No | Old British | Euronorm | Swedish SS | Japanese JIS |
| BS | En | No | Name |
| 2205 | S31803 / S32205 | 318S13 | - | 1.4462 | X2CrNiMoN22-5-3 | 2377 | SUS 329J3L |
Grade specification comparisons for 2205 grade stainless steels
| Grade | Reasons for choosing the grade |
| 904L | Better formability is needed, with similar corrosion resistance and
lower strength. |
| UR52N+ | High resistance to corrosion is required, e.g. resistance to higher
temperature seawater. |
| 6%Mo | Higher corrosion resistance is required, but with lower strength
and better formability. |
| 316L | The high corrosion resistance and strength of 2205 are not needed.
316L is lower cost. |
Heat ResistanceGrade 2205 stainless steel exhibits excellent
corrosion resistance, much higher than that of grade 316. It
resists localized corrosion types like intergranular, crevice and
pitting. The CPT of this type of stainless steel is around 35°C.
This grade is resistant to chloride stress corrosion cracking (SCC)
at temperatures of 150°C. Grade 2205 stainless steels are apt
replacements to austenitic grades, especially in premature failure
environments and marine environments.
The high oxidation resistance property of Grade 2205 is marred by
its embrittlement above 300°C. This embrittlement can be modified
by a full solution annealing treatment. This grade performs well at
temperatures below 300°C.
Heat Treatment
The best suited heat treatment for this grade is solution treatment
(annealing), between 1020 - 1100°C, followed by rapid cooling.
Grade 2205 can be work hardened but cannot be hardened by thermal
methods.
Welding
Most standard welding methods suit this grade, except welding
without filler metals, which results in excess ferrite. AS 1554.6
pre-qualifies welding for 2205 with 2209 rods or electrodes so that
the deposited metal has the right balanced duplex structure.
Adding nitrogen to the shielding gas ensures that adequate
austenite is added to the structure. The heat input must be
maintained at a low level, and the use of pre or post heat must be
avoided. The co-efficient of thermal expansion for this grade is
low; hence the distortion and stresses are lesser than that in
austenite grades.
Machining
The machinability of this grade is low due to its high strength.
The cutting speeds are almost 20% lower than that of grade 304.
Fabrication
The fabrication of this grade is also affected by its strength.
Bending and forming of this grade requires equipment with larger
capacity. Ductility of grade 2205 is lesser than austenitic grades;
therefore, cold heading is not possible on this grade. In order to
carry out cold heading operations on this grade, intermediate
annealing should be carried out.
Applications
Some of the typical applications of duplex steel grade 2205 are
listed below:
- Oil and gas exploration
- Processing equipment
- Transport, storage and chemical processing
- High chloride and marine environments
- Paper machines, liquor tanks, pulp and paper digesters
