2507 Super Duplex Stainless Steel: A Comprehensive Analysis of Performance and Applications

Super duplex stainless steel 2507 is a material designed to provide exceptional strength and corrosion resistance under harsh conditions. It contains 25% chromium, 4% molybdenum, and 7% nickel. These components endow the alloy with excellent resistance to chloride pitting and crevice corrosion, while its duplex structure provides unique resistance to chloride stress corrosion cracking. It is recommended to limit the use of 2507 alloy to applications below 600°F (316°C), as prolonged exposure to higher temperatures may reduce its toughness and corrosion resistance.

 

 

1. Performance Characteristics

 

Excellent Corrosion Resistance: Super duplex stainless steel 2507 exhibits extremely high uniform corrosion resistance to organic acids (such as formic acid and acetic acid) and also demonstrates excellent resistance to inorganic acids, especially chloride-containing inorganic acids. The ferrite portion of the alloy makes it resistant to stress corrosion cracking in warm, chloride-containing environments. Increased chromium, molybdenum, and nitrogen content enhances its resistance to localized corrosion (such as pitting and crevice corrosion).

High Strength: The yield strength of 2507 alloy is higher than that of 304 and 316 stainless steel. Thinner layers of 2507 material can often achieve the same structural strength as thicker nickel alloys, significantly reducing overall weight and manufacturing costs.

Good Machinability: Easy to weld using various standard welding methods without the need for preheating or post-weld annealing. It has good cold working properties, but lower plasticity, making forming operations more difficult and requiring higher initial forming pressure.

 

2. Application Areas

 

Seawater Desalination Equipment: Used in the seawater desalination process to manufacture various components that come into contact with seawater, such as pipes, valves, and heat exchangers, resisting seawater corrosion.

Chemical Equipment: Suitable for pressure vessels, pipes, and heat exchangers in chemical processing, resisting corrosion from chemical media.

Marine Applications: Widely used in shipbuilding and marine engineering structures, such as hull components, offshore platforms, and pipeline systems, resisting corrosion from seawater and marine environments.

Flue Gas Desulfurization Equipment: Used in flue gas desulfurization systems in the power industry to manufacture components such as absorption towers, spray layers, and pipelines, resisting corrosion from acidic gases and liquids.

Pulp and Paper Equipment: Used in the pulp and paper production process to manufacture various equipment and components, resisting corrosion from pulp and chemicals.

Oil and Gas Industry Equipment: Used in the oil and gas industry to manufacture oil and gas field pipelines, valves, and equipment, resisting corrosive environments containing hydrogen sulfide and carbon dioxide.

 

3. Machining and Manufacturing

 

Machining: Lower cutting speeds and constant feed rates are recommended to reduce the alloy's work hardening tendency. Due to its higher hardness than 304 and 316 stainless steel, and the longer, fibrous chips, a chip breaker is recommended.

Forming: Due to its high initial yield strength, the forming pressure must be higher than that required for standard 300 series stainless steel. Lower plasticity will make forming operations difficult.

Welding: Various welding techniques, including GTAW, SAW, and GMAW, can be used. Preheating and post-weld annealing are not required. The filler metal should be a modified ferritic/austenitic type, such as 2205, Super duplex stainless steel 2507, or 2304.

Hot Working: The recommended forming method. Heating to 1750-2000°F followed by rapid cooling. For maximum performance, the material should be fully annealed after processing.

Hot Working: The recommended forming method. Heating to 1750-2000°F followed by rapid cooling. For maximum performance, the material should be fully annealed after processing.

 

4. Chemical Composition and Physical Properties

 

Chemical Composition (%): Carbon (C) ≤0.03%, Nitrogen (N) 0.24%-0.32%, Silicon (Si) ≤0.8%, Phosphorus (P) ≤0.035%, Sulfur (S) ≤0.02%, Chromium (Cr) 24.0%-26.0%, Manganese (Mn) ≤1.2%, Iron (Fe) Balance, Nickel (Ni) 6.0%-8.0%, Copper (Cu) ≤0.5%, Molybdenum (Mo) 3.0%-5.0%.

Physical properties: Density 7.75 g/cm³ (room temperature), specific heat capacity 0.12 Kcal/kg・°C (20°C), melting range 1410°C - 1460°C, elastic modulus 200 KN/mm² (20°C), resistivity 80 µΩ・cm (20°C), coefficient of thermal expansion 13.0 µm/m・°C (20°C - 100°C), thermal conductivity 17.0 W/m・°K (20°C).

Super duplex stainless steel 2507 Mechanical properties: Tensile strength 116 ksi, 0.2% yield strength 80 ksi, elongation 15%.