Alloy 2304 (UNS S32304) is a 23% chromium, 4% nickel, molybdenum-free duplex stainless steel. The Alloy 2304 has corrosion resistance properties similar to 316L. Furthermore, its mechanical properties, i.e., yield strength, are twice those of 304L/316L austenitic grades. This allows the designer to save weight, particularly for properly designed pressure vessel applications.

Grade Specification

• ASTM/ASME: UNS S32304
• EURONORM: FeMi35Cr20Cu4Mo2
• DIN: 2.4660

Composition

Mechanical Properties

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

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

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.

APPLICATIONS:

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

• Chloride containing environments
• Welded pipe systems within the Pulp and Paper, Chemical and Petrochemical, and Water Treatment industries
• Transportations
• Heat exchanger tubes
• Architecture, building, construction
• Pressure vessels
• Caustic solutions, organic acids
• Food industry