ASTM A890 5A | CE3MN & J93404 | Duplex 2507

ASTM A890 5A is a casting duplex stainless steel alloy known for its high strength and excellent corrosion resistance. It is designated as UNS J93404 or ACI CE3MN. Grade 5A has the nominal composition of 25Cr-7Ni-Mo-N, which is equivalent to Duplex 2507 (UNS S32750). ASTM A890 5A castings, either furnished in the product form of valve, bar or pump, are characterized by outstanding resistance to pitting corrosion, crevice corrosion, stress corrosion cracking, and high mechanical strength. They are particularly suitable for applications in harsh environments such as marine applications, chemical reactors, oil and gas pipelines, and seawater pumps.

A ball valve made from ASTM A890 Gr.5A castings, 4″ 150LB floating type.

Chemical Composition Requirements

Mechanical Properties

Corrosion Resistance

The ASTM A890 5A cast impeller for a slurry pump.

One of the major advantages of ASTM A890 Grade 5A is its outstanding corrosion resistance. It has significant resistance to pitting corrosion, crevice corrosion, and stress corrosion cracking, making it particularly suitable for marine, chemical, and oil & gas industries. The primary contributors to its corrosion resistance are the high levels of chromium (Cr), molybdenum (Mo), and nitrogen (N).

• Pitting and Crevice Corrosion: The high molybdenum content (4.0 – 5.0%) provides excellent resistance to pitting and crevice corrosion, especially in chloride environments.
• Stress Corrosion Cracking: The duplex microstructure (austenite + ferrite) enhances the material’s ability to resist stress corrosion cracking, making it ideal for harsh marine and petrochemical environments.
• Seawater Corrosion Resistance: The molybdenum addition significantly improves its resistance to seawater, making it highly reliable for use in marine engineering.

Manufacture & Heat Treatment

ASTM A890 round bars ready for dispatch to Saudi Arabia.

ASTM A890 5A castings shall be made by the electric furnace process usually with separate refining such as argon-oxygen-decarburization (AOD). Due to its high strength and hardness, Grade 5A requires carbide tools and careful control of cutting speeds to avoid excessive wear on tooling. After casting, the material is usually subjected to a solution treatment, in which it is heated to a temperature no less than 1120°C, held for sufficient time to heat the casting uniformly, furnace cooled to no less than 1045°C, then quenched in water. This heat treatment is conducted to prevent the formation of detrimental phases (such as sigma phase) and ensure the best mechanical and corrosion properties.

Applications

Thanks to its unique mechanical properties and corrosion resistance, ASTM A890 Grade 5A is widely used in various industries:

• Marine Engineering: Components such as offshore platforms, seawater pumps, and propellers.
• Chemical Industry: Reactors, pipelines, and heat exchangers for handling corrosive chemicals.
• Oil and Gas: Oil and gas pipeline systems, pumps, and downhole equipment.
• Desalination: Seawater reverse osmosis units and seawater desalination plants.
• Desulfurization & Dechlorination: Equipment for handling corrosive gases.