ThePipingMart Blog Grades 2304 Duplex Steel (UNS S32304) – Composition, Properties, and Uses

2304 Duplex Steel (UNS S32304) – Composition, Properties, and Uses

2304 Duplex Steel

Duplex Steel UNS S32304 is a type of stainless steel alloy that provides superior corrosion resistance, strength, and durability. This grade of stainless steel is widely used in a variety of industries, including chemical processing and marine applications. In this blog post, we will take a closer look at the composition, properties, uses, and machining techniques associated with this unique stainless steel alloy.

2304 Duplex Steel Chemical Composition

Duplex Steel UNS S32304 contains 20-22% chromium and 3-3.5% molybdenum. It also contains small amounts of nitrogen, manganese, iron, silicon, carbon, sulfur and phosphorus.

Carbon Chromium Nickel Molybdenum Nitrogen Others
0.020 23 4 0.2 0.1 S=0.001

2304 Duplex Steel Chemical Properties

This grade of stainless steel has excellent resistance to pitting and crevice corrosion when exposed to chloride environments. It also has good weldability and formability due to its austenitic-ferritic microstructure.

2304 Duplex Steel Mechanical Properties

Duplex Steel UNS S32304 offers superior strength compared to other grades of stainless steel alloys. It yields strengths over 50ksi (345 MPa) in some cases while exhibiting elongations over 30%. The alloy exhibits excellent impact toughness as well as excellent fatigue strength when exposed to cyclic loading conditions.

°C Rp 0.2
Rp 1.0
Rp 1.0
°F YS 0.2%
Offset KSI
YS 0.1%
Offset KSI
20 400 440 600 68 58 64 87 25
100 330 365 570 212 48 53 83 25
200 280 310 530 392 41 45 77 20
300 230 260 490 572 33 38 71 20

2304 Duplex Steel Physical Properties

The alloy has a high thermal conductivity which means it can quickly dissipate heat generated during machining operations or welding processes. It also exhibits good electrical resistivity, which makes it suitable for use in electrical components or wiring systems that require resistance to corrosion or high temperatures.

°C Resistivity
(μ_ cm)
20-100 13 20 80 17 450 200 75
20-100 13 100 92 18 500 190 73
20-200 13.5 200 100 19 530 180 70
20-300 14 300 105 20 560 170 67

2304 Duplex Steel Equivalent

  • ASTM A240.
  • ASTM A276.
  • ASTM A480.
  • ASTM A789.
  • ASTM A790.
  • DIN 1.4362.

2304 Duplex Steel Uses

The combination of corrosion resistance, strength and durability make Duplex Steel UNS S32304 an ideal material for applications ranging from chemical processing equipment to storage tanks used in marine environments. It is also commonly used in offshore oil rigs due to its ability to withstand harsh environments without corroding or cracking under high pressures or temperatures.

Corrosion Resistance

As a part of the super-austenitic family, Duplex Steel UNS S32304 offers excellent corrosion resistance – one of its most noteworthy qualities. It can withstand corrosion in a multitude of application settings, ranging from locations exposed to pitting to those facing chloride stress corrosion cracking. This stainless steel alloy also provides greater corrosion resistance at higher temperatures than conventional austenitic stainless steel grades. Additionally, compared to traditional ferrite and austenite steels, the degree of resistance increases with its rising temperature. Not only is it highly resistant to pitting and chloride-induced stress cracking, but it boasts strong sulfuric acid and hydrochloric acid de-aeration performance as well. All these beneficial qualities put together make Duplex Steel UNS S32304 an ideal choice for companies looking for maximum protection against long-term corrosion.

Heat Resistance

Duplex Steel UNS S32304 has excellent heat resistance up to 500ºF (260ºC). However, exposure beyond 500ºF can cause oxidation unless the material is properly treated with a protective coating such as aluminium oxide or zinc oxide before exposure occurs.

Heat Treatment

Heat treatment processes such as annealing or quench hardening are not recommended for this grade of stainless steel as they may cause embrittlement at room temperature due to sensitization from exposure to elevated temperatures during the heat treatment process.


Machining operations on Duplex Steel UNS S32304 should be performed using standard machining techniques such as turning, drilling and milling operations with carbide cutting tools capable of providing accurate cuts with minimal wear on the cutting tools themselves. The material’s hardness makes it more difficult to machine than other grades, so higher speeds may be required for efficient machining operations depending on the quality of the cutting tools being used for the operation itself.


Welding processes should always be conducted using weldable filler metals designed specifically for duplex stainless steels such as 2209 E2209 TIG rods or 309L MIG wires in order to ensure proper welding performance without compromising on weld integrity or corrosion protection capabilities offered by these fillers metals specifically designed for duplex steels like UNS S32304.


Duplex Steel UNS S32304 offers an ideal combination of strength, durability, and corrosion resistance, making it an ideal choice for many industrial applications where these characteristics are needed, such as offshore oil rigs, chemical processing equipment, storage tanks, etc. Its machinability can be challenging, but this can be overcome with higher speeds when using high-quality cutting tools. Additionally, its welding characteristics require specific fillers and metals made specifically for duplex steels in order to achieve optimal performance. All things considered, Duplex Steel UNS S32304 is an extremely versatile material whose properties make it suitable for many different types of applications.

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