Duplex 2205 (UNS S31803, S32205) - A Nitrogen Enhanced Duplex Stainless Steel

Duplex 2205 is a nitrogen enhanced duplex stainless steel developed for combating common corrosion issues encountered with the 300 series stainless steels. Yaang Pipe Industry Co., Limited supplies duplex and super duplex stainless steels in plate, sheet, bar, pipe, pipe fittings, flanges, tube and weld wire.

“Duplex” is a stainless steel family that is neither fully austenitic, such as 304 stainless, nor ferritic such as 430 stainless steel. The 2205 duplex stainless steel structure consists of austenite pools surrounded by a continuous ferrite phase. In the annealed condition, 2205 has approximately 40-50% ferrite. The 2205 Duplex is mostly referred to as the work horse grade and is the most widely used grade in the duplex family of stainless steels.

The benefit of a duplex structure is that the favorable qualities of a ferritic alloy are combined with those of an austenitic alloy that features corrosion resistance and ease of fabrication. Usage of 2205 Duplex stainless steel should be limited to temperatures below 600° F. Extended elevated temperature exposure can embrittle 2205 stainless.

Chemical Composition, %

The chemical composition of 2205 Duplex is:

Cr	Ni	Mo	C	N	Mn	Si	P	S	Fe
22.0-23.0	4.50-6.50	3.00-3.50	.030 Max	0.14-0.20	2.00 Max	1.00 Max	.030 Max	.020 Max	Balance

Corrosion Resistance

The 2205 duplex stainless steel is an economical solution for a number of applications where the 300 series stainless steels are susceptible to chloride stress corrosion cracking. Stress corrosion cracking occurs when stainless steels are subjected to tensile stress, while in contact with solutions containing chlorides. The susceptibility of stainless steels to stress corrosion cracking is also increased by increasing temperatures.

Combining molybdenum, chromium and nitrogen result in 2205 having good resistance to chloride pitting and crevice corrosion. This resistance is highly important for services such as marine environments, brackish water, bleaching operations, closed loop water systems and some food processing applications. The high chromium, molybdenum and nitrogen contents of 2205 offer corrosion resistance superior to common stainless steels, such as, 316L and 317L in most environments.

Mechanical Properties (Specified Tensile Properties ASTM A240)

The mechanical properties of Duplex 2205 are provided in the table:

Ultimate Tensile Strength, ksi Minimum	.2% Yield Strength, ksi Minimum	Hardness Max.
95	65	31 Rockwell C

Forms of Duplex 2205

The available forms of Duplex 2205 are:

• Duplex 2205 Pipes & Duplex 2205 Tubes (welded & seamless)
• Duplex 2205 Pipe Fittings (i.e., duplex 2205 flanges, slip-ons, blinds, weld-necks, lapjoints, long welding necks, socket welds, elbows, tees, stub-ends, returns, caps, crosses, reducers, and pipe nipples)

ASTM Specifications

Pipe Smls	Pipe Welded	Tube Smls	Tube Welded	Sheet/Plate	Bar	Flanges, Fittings & Valves
A790	A790	A789	A789	A240	A276	A182

Applications

The applications of Duplex 2205 are:

• Chemical process vessels In what applications, piping and heat exchangers
• Flue gas desulfurization equipment
• Pulp mill digesters, bleach washers, chip pre-steaming vessels
• Food processing equipment
• Oil field piping and heat exchangers.

This information has been sourced, reviewed and adapted from materials provided by Yaang Pipe Industry Co., Limited.

For more information on this source, please visit Yaang Pipe Industry Co., Limited.

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