UNS S32750, commonly known as 2507, is a super duplex stainless steel (SDSS) that combines austenitic and ferritic microstructures. It is widely recognized for its exceptional strength, superior corrosion resistance, and versatility in harsh industrial environments.

Core Characteristics

Chemical Composition: Typical alloying elements include 24-26% chromium (Cr), 6-8% nickel (Ni), 3-5% molybdenum (Mo), 0.24-0.32% nitrogen (N), and iron (Fe) as the balance. Low carbon content (≤0.03%) minimizes intergranular corrosion risk.

Mechanical Properties: Offers high tensile strength (≥690 MPa) and yield strength (≥450 MPa) at room temperature, roughly twice that of conventional austenitic stainless steels like 316L. It maintains excellent toughness with an elongation rate of ≥25% and impact energy (KV) of ≥47 J at -40℃.

Corrosion Resistance: Excels in resisting pitting, crevice corrosion, and stress corrosion cracking (SCC), especially in chloride-rich environments. Its Critical Pitting Temperature (CPT) is ≥40℃ (20% NaCl solution), and Critical Crevice Corrosion Temperature (CCT) is ≥35℃. It also performs well in seawater, acidic media, and industrial chemicals.

Key Applications

Marine Engineering: Seawater desalination plants, ship hulls, offshore oil and gas platforms, and subsea pipelines.

Petrochemical Industry: Oil and gas exploration equipment, chemical reactors, pipelines for corrosive fluids, and refining facilities.

Other Sectors: Pulp and paper bleaching systems, wastewater treatment plants, high-pressure boilers, and structural components in aggressive chloride environments.

Processing & Usage Notes

Suitable for various processing methods, including hot working (forging, rolling), cold working (stamping, bending), and welding (using matching duplex stainless steel welding wires).

Recommended operating temperature range: -50℃ to 315℃ for long-term service.

Complies with international standards such as ASTM A480/A480M and ASME SA-240M.

1. Core Specifications & Chemical Composition

Chemical Composition (Mass Fraction, %)

Mechanical Properties (Room Temperature, Solution Annealed)

2. Corrosion Resistance Performance

• Pitting Resistance: Critical Pitting Temperature (CPT) ≥40℃ (20% NaCl solution), far exceeding 316L’s ~25℃.

• Crevice Corrosion Resistance: Critical Crevice Corrosion Temperature (CCT) ≥35℃ (20% NaCl solution), suitable for chloride-rich environments.

• Seawater Corrosion: Corrosion rate ≤0.01 mm/year (30℃ artificial seawater, 90-day immersion).

• Acid Resistance: Corrosion rate ≤0.1 mm/year in 5% H₂SO₄ solution (room temperature); resistant to dilute hydrochloric acid and organic acids.

• Stress Corrosion Cracking (SCC): Immune to SCC in chloride-containing environments, a common failure point for austenitic stainless steels.

 4. Key Applications

• Marine Engineering: Seawater desalination plants, offshore oil/gas platforms, subsea pipelines, shipboard equipment.
• Petrochemical Industry: Oil exploration tools, chemical reactors, corrosive fluid pipelines, refining units.
• Pulp & Paper Industry: Bleaching equipment, digesters, and chemical handling systems.
• Other Sectors: Wastewater treatment plants, high-pressure boilers, pharmaceutical equipment, and structural components in chloride-rich environments.

5. Processing & Usage Guidelines

• Processing: Compatible with hot working (forging, rolling, extrusion), cold working (stamping, bending, cutting), and welding (use matching duplex stainless steel wires; preheating not required, post-weld heat treatment optional).
• Operating Temperature: -50℃ to 315℃ (long-term service); short-term use up to 400℃.
• Standards Compliance: Meets ASTM A480/A480M, ASME SA-240M, EN 1.4410, and GB/T 21832-2015.