Duplex 2304 Stainless Steel (UNS S32304)

Duplex 2304 is a 23% chromium, 4% nickel, molybdenum-free duplex stainless steel whose structure is a balance of ferritic and austenitic. It has general corrosion resistance similar or better than Alloys 304L and 316L but with yield strength nearly double that of austenitic stainless steels. Its duplex microstructure and low nickel and high chromium contents also allows Duplex 2304 to demonstrate improved stress corrosion resistant properties compared to 304 and 316. It is typically suitable for all applications in the -58oF to 572oF (-50oC to 300oC) temperature range and is designed to feature high mechanical strength, good weldability, good corrosion resistance, high resistance to stress corrosion cracking, good machinability, low thermal expansion, good fatigue properties, high thermal conductivity, and easy fabrication.

Specifications: UNS S32304

Applications:

Duplex 2304 is generally used in the same applications in which Alloys 304 and 316L are used. Some examples of these applications include:

1. Chloride containing environments

2. Welded pipe systems within the Pulp and Paper, Chemical and Petrochemical, and Water Treatment industries

3. Transportations

4. Heat exchanger tubes

5. Architecture, building, construction

6. Pressure vessels

7. Caustic solutions, organic acids

8. Food industry

Standards:

1. ASTM/ASME: UNS S32304

2. EURONORM: FeMi35Cr20Cu4Mo2

3. DIN: 2.4660

Corrosion Resistance:

1. Due to its high chromium content of 23%, the corrosion resistance properties of Duplex 2304 are practically equivalent to those of Alloy 316L

2. Its duplex microstructure and low nickel and high chromium contents allows Duplex 2304 to have improved stress corrosion resistance properties compared to the 304L and 316L standard austenitic grades.

3. More resistant to pitting and crevice corrosion resistance that Alloy 316L

4. Outperforms Alloys 304L and 316L in stress corrosion cracking resistance in chloride containing aqueous solutions

5. Its corrosion rate in boiling nitric acid (65%) is higher than that of Alloy 316L

6. Its high yield strength allows Duplex 2304 to perform well in abrasion/corrosion applications

Structure

1. Microstructure of Duplex 2304 is very stable compared to molybdenum containing duplex stainless steels

2. Contains approximately equal amounts of ferritic and austenitic in microstructure after annealing in a temperature about

Weldability

1. Can be successfully welded by TIG manual and automatic, PLASMA, MIG, SMAW, SAW, FCAW

2. Duplex microstructure renders the alloy less sensitive to hot cracking

3. Pre-heating and post welding is not required

4. Filler metal should be a balanced ferrite/austenitic type

 Machinability

1. Exhibits improved machinability properties particularly when considering drilling

2. Low speeds and high feeds will minimize this alloys tendency to work harden

Composition

C

Cr

Fe

Mn

Si

S

P

Ni

Cu

N

Duplex

2304

0.03

max

min: 21.5

max:24.5

Bal.

2.5

max

1.0

max

0.03

max

0.04

maxmin:3.0 max:3.5

min:0.05

max: 2.0

min: 0.05

max: 2.0

Mechanical Properties

Grade

Tensile Strength ksi (MPa)

min

Yield Strength 0.2% offset ksi (MPa)

min

Elongation (% in 50mm) min

Hardness (Brinell)

MAX

Hardness

(Rockwell B)

MAX

Duplex 2304

87

(600)

58

(400)

25

293

31j

Physical Properties

Duplex 2304

Density at 68°F (20°C)

0.28 lbm/in3

7800 kg/cm3

Coefficient of Thermal Expansion

ax10-6°C-1

68°F to: 212°F

(20 -100°C)

13

68°F to 392°F

(20 -200°C)

13.5

68°F to 572°F

(20 -300°C)

14

Thermal Conductivity

W.m-1.K-1

at 68°F (20°C)

17

at 212°F (100°C)

18

at 392°F (200°C)

19

at 572°F (300°C)

20

Electrical Resitivity

(µ_ cm)

at 68°F (20°C)

80

at 212°F (100°C)

92

at 392°F (200°C)

100

at 572°F (300°C)

105

Specific Heat

(Btu/lb/°F)

32°F to: 212°F

(20 -100°C)

0.11