Core Parameter Comparison
The table below outlines the fundamental differences between 2205 and 2507 duplex steel flanges for a quick overview.
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Feature
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2205 Duplex Steel Flange
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2507 Duplex Steel Flange (Super Duplex)
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|---|---|---|
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Key Alloy Composition
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Approx. 22% Chromium, 3% Molybdenum, 0.15-0.18% Nitrogen
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Approx. 25% Chromium, 4% Molybdenum, 0.24-0.32% Nitrogen
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|
Yield Strength
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≥450 MPa
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≥550 MPa
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|
Pitting Resistance (PREN)
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~34-38
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>40
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Corrosion Resistance
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Excellent, particularly resistant to chloride stress corrosion cracking
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Superior, with stronger resistance to pitting, crevice, and general corrosion
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Typical Applications
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Chemical processing, oil & gas, standard seawater environments, wastewater treatment
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Harsh environments: Seawater desalination, offshore oil platforms, high-concentration chlorides or acidic media
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|
Cost Consideration
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More cost-effective, offering good value
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Higher material and processing costs, larger initial investment
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🔬 Detailed Performance and Selection Guidance
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Corrosion Resistance: The Primary DifferentiatorThe key difference lies in their ability to withstand corrosive environments. While 2205 offers excellent resistance to chloride stress corrosion cracking and performs well in many chemical and seawater applications , 2507 is significantly more robust. Its higher content of chromium, molybdenum, and nitrogen provides it with exceptional resistance to pitting and crevice corrosion, making it the preferred choice for more aggressive environments like concentrated chloride solutions, acidic conditions, and seawater desalination plants .
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Mechanical Strength and Weight Implications2507 duplex steel has a higher mechanical strength compared to 2205. Its yield strength can exceed 550 MPa, which is approximately twice that of standard austenitic stainless steels like 316L and also higher than 2205 . This high strength allows for the design of thinner and lighter components without compromising safety or pressure ratings, which is particularly advantageous in high-pressure applications and for reducing overall structural weight, such as in offshore platforms .
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Application-Based Selection Guidelines
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For highly corrosive media: If the application involves high concentrations of chloride ions, sulfides, or strong acids (e.g., in seawater desalination, offshore oil and gas equipment, or harsh chemical processing), 2507 is the more reliable and often the necessary choice due to its superior corrosion resistance .
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For standard corrosive conditions: For environments with general corrosion, mildly chlorinated water, or wastewater treatment, 2205 is typically sufficient and more economical .
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Considering total cost: Although 2507 has a higher initial cost, its longer service life and reduced maintenance needs in extreme conditions can lead to a lower total cost of ownership over the project’s lifecycle .
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Special Considerations for Fabrication and UseBoth grades require controlled heat treatment, typically involving solution annealing at around 1040-1100°C followed by rapid cooling (e.g., water quenching) to prevent the precipitation of brittle intermetallic phases that can impair toughness and corrosion resistance . It is important to note that 2507 is not recommended for prolonged use at temperatures above 300°C (570°F), as embrittlement can occur .
In summary, the choice between 2205 and 2507 duplex steel flanges boils down to finding the optimal balance between the specific corrosion demands and mechanical requirements of your application and your budget constraints. For environments where 2205 is adequate, it represents a cost-effective and reliable solution. However, for extreme conditions where safety and longevity are paramount, investing in 2507 is essential.