Duplex Stainless Steel – UNS S31803 / AISI 2205

UNS S31803 / AISI 2205
“Duplex stainless steels” has a two phase micro structure consisting of ferritic and austenitic stainless steel granules. When duplex stainless steel is melted it solidifies from the liquid phase to a completely ferritic structure. As the material cools to room temperature, about half of the ferritic grains transform to austenitic grains. The result is a microstructure of roughly 50% austenite and 50% ferrite.
duplex stainless steel
Duplex stainless steel Microstructure of base metal of the duplex stainless steel, 2205, 250X original magnification. Austenite phases are present as white island in blue sea of ferrite. Duplex stainless steels have a two-phase microstructure of austenite and ferrite grains. The picture shows the yellow austenitic phase as “islands” surrounded by the blue ferritic phase.
Introduction

Stainless steels are high-alloy steels. These steels are available in four groups that include martensitic, austenitic, ferritic and precipitation-hardened steels. These groups are formed based on the crystalline structure of stainless steels.

Stainless steels contain larger amounts of chromium in comparison with other steels and thus have good corrosion resistance. Most of the stainless steels contain about 10% of chromium.

Grade 2205 stainless steel is a duplex stainless steel whose design enables combining improved resistance to pitting, high strength, stress corrosion, crevice corrosion and cracking. Grade 2205 stainless steel resists sulfide stress corrosion and chloride environments.

duplex stainless steel 2205
duplex stainless steel – 2205 grade
The following datasheet provides an overview of grade 2205 duplex stainless steel.
Chemical Composition
The chemical composition of grade 2205 stainless  steel is outlined in the following table.
Table.1
Chemical Composition
Element
Content (%)
Iron, Fe
63.75-71.92
Chromium, Cr
21.0 – 23.0
Nickel, Ni
4.50 – 6.50
Molybdenum, Mo
2.50 – 3.50
Manganese, Mn
2.00
Silicon, Si
1.00
Nitrogen, N
0.080 – 0.20
Carbon, C
0.03
Phosphorous, P
0.03
Sulfur, S
0.02

The duplex structure gives this family of stainless steels a combination of attractive properties:

Strength: Duplex stainless steels are about twice as strong as regular austenitic or ferritic stainless steels.

Toughness and ductility: Duplex stainless steels have significantly better toughness and ductility than ferritic grades; however, they do not reach the excellent values of austenitic grades.

Corrosion resistance: As with all stainless steels, corrosion resistance depends mostly on the composition of the stainless steel. For chloride pitting and crevice corrosion resistance, their chromium, molybdenum and nitrogen content are most important. Duplex stainless steel grades have a range of corrosion resistance, similar to the range for austenitic stainless steels, i.e from Type 304 or 316 (e.g. LDX 2101©) to 6% molybdenum (e.g. SAF 2507©) stainless steels.

Stress corrosion cracking resistance: Duplex stainless steels show very good stress corrosion cracking (SCC) resistance, a property they have “inherited” from the ferritic side. SCC can be a problem under certain circumstances (chlorides, humidity, elevated temperature) for standard austenitics such as Types 304 and 316.

Cost: Duplex stainless steels have lower nickel and molybdenum contents than their austenitic counterparts of similar corrosion resistance. Due to the lower alloying content, duplex stainless steels can be lower in cost, especially in times of high alloy surcharges. Additionally, it may often be possible to reduce the section thickness of duplex stainless steel, due to its increased yield strength compared to austenitic stainless steel. The combination can lead to significant cost and weight savings compared to a solution in austenitic stainless steels.

Mechanical Properties

The mechanical  properties of grade  2205 stainless  steel are displayed  in the following table.

Table 2. Mechanical Properties of Duplex Stainless Steel / UNS S31803 / AISI 2205

Table 2.
Mechanical Properties
Properties
Metric
Imperial
Tensile strength at break
621 MPa
90000 psi
Yield strength (@strain 0.200 %)
448 MPa
65000
psi
Elongation at break (in 50 mm)
25.0%
25.0%
Hardness, Brinell
293
293
Hardness, Rockwell c
31.0
31.0
Other Designations
Equivalent materials to grade 2205 duplex stainless steel are:
  • ASTM A182 Grade F51
  • ASTM A240
  • ASTM A789
  • ASTM A790
  • DIN 1.4462

Applications :

Grade  2205 duplex stainless  steel  is  used  in  the  following applications:
  • Fuel gas filters
  • Chemical tanks
  • Heat exchangers
  • Acetic acid distillation components

References:

  1. https://en.wikipedia.org/wiki/Duplex_stainless_steel
  2. https://www.imoa.info/
  3. https://www.steeltank.com/
  4. http://www.corrosionlab.com/
  5. http://mit.imt.si/Revija/izvodi/mit114/tehovnik.pdf

FOR FUTHER INFORMATION PLEASE CONTACT :

PT. STEELINDO PERSADA
Email    : marketing.steelindopersada@gmail.com or contact@steelindopersada.com

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  1. Pingback: SS 316 - Austenitic Stainless Steel Grade - Steelindo Persada

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