2205 stainless steel

2205 stainless steel is the most widely used duplex (ferritic/austenitic) stainless steel grade. It finds applications due to both excellent corrosion resistance and high strength.

Chemical Formula of 2205 stainless steel

Fe, <0.03% C, 21-23% Cr, 4.5-6.5% Ni, 2.5-3.5% Mo, 0.8-2.0% N, <2% Mn, <1% Si, <0.03% P, <0.02% S

              2205 stainless steel nut

2205 stainless steel applications

Chemical processing, transport and storage.

Oil and gas exploration and processing equipment

Marine and other high chloride environments

Pulp and paper digesters, liquor tanks and paper machines

2205 is not generally suitable for use at temperatures above 300°C as it suffers from precipitation of brittle micro-constituents, nor below -50°C because of its ductile-to-brittle-transition.

These properties are specified for flat rolled product (plate, sheet and coil) in ASTM A240/A240M. Similar but not necessarily identical properties are specified for other products such as pipe and bar in their respective specifications.

The standard S31803 composition has over the years been refined by many steel suppliers, and the resulting restricted composition range was endorsed as UNS S32205 in 1996. S32205 gives better guaranteed corrosion resistance, but much of the S31803 currently produced also complies with S32205.

Typical compositional ranges for grade 2205 stainless steels are given in table 1.

Typical mechanical properties for grade 2205 stainless steels are given in table 2.

Typical physical properties for grade 2205 stainless steels are given in table 3.

 Approximate grade comparisons for 2205 stainless steels are given in table 4.

 Possible Alternative Grades

2205 stainless steel heat treatment

Solution treatment (annealing) - heat to 1020-1100°C and cool rapidly. This grade cannot be hardened by thermal treatment, but does work harden.

Corrosion Resistance of 2205 stainless steel

Excellent general corrosion resistance; superior to Grade 316 in most environments. Excellent resistance to localised corrosion including intergranular, pitting and crevice corrosion; the CPT of 2205 is generally at least 35°C. The grade is also resistant to chloride stress corrosion cracking (SCC) at temperatures of up to about 150°C. Grade 2205 will often perform well in environments which cause premature failure of austenitic grades. It has better resistance to sea water than grade 316. See more about the corrosion ressitance of 304 stainless steel

Heat resistance of 2205 stainless steel

Although 2205 has good high temperature oxidation resistance this grade, like other duplex stainless steels, suffers from embrittlement if held for even short times at temperatures above 300°C. If embrittled this can only be rectified by a full solution annealing treatment. Duplex stainless steels are almost never used above 300°C.

How to fabricate 2205 stainless steel

The high strength of 2205 also makes bending and forming more difficult; these operations will require larger capacity equipment than would be required for austenitic stainless steels. The ductility of 2205 is less than that of an austenitic grade, so severe forming operations, such as cold heading, are not generally possible. If severe cold working is required it is recommended that intermediate annealing be carried out.

Welding 2205 stainless steel

Weldable by all standard methods, but should not generally be welded without filler metal as this may result in excessive ferrite. AS 1554.6 pre-qualifies welding of 2205 with 2209 rods or electrodes to ensure that deposited metal has the correctly balanced duplex structure. Nitrogen added to the shielding gas will also assist in ensuring adequate austenite in the structure. Heat input must be kept low and no pre- or post-heat should be used. The lower co-efficient of thermal expansion of all duplex stainless steels compared with austenitic grades reduces distortion and associated stresses.

Machining 2205 stainless steel

The high strength that makes 2205 useful in many applications also reduces its machinability. Cutting speeds are approximately 20% slower than for grade 304. There is as yet no Improved Machinability version of 2205.