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The Super Duplex 2507 Hex Domed Cap Nut, manufactured to DIN1587 standard, is a threaded fastener produced from Super Duplex Stainless Steel 2507. This fastener combines a domed cap configuration with duplex stainless steel properties, designed for industrial environments involving chloride exposure, high mechanical loads, and temperature variations. The domed cap structure covers exposed bolt threads, while the duplex microstructure provides balanced mechanical strength and corrosion resistance for commercial procurement across multiple sectors.
The 2507 duplex stainless steel contains a precisely controlled blend of alloying elements:
Alloy | Ni | Cr | Mo | N | C | Mn | Si | S | P | Cu | |
2507 | Min. | 6.0 | 24 | 3.0 | 0.24 | - | - | - | - | - | - |
Max. | 8.0 | 26 | 5.0 | 0.32 | 0.03 | 1.2 | 0.8 | 0.02 | 0.035 | 0.5 |
This chemical formulation creates a dual-phase microstructure consisting of approximately 50% ferrite and 50% austenite, with a Pitting Resistance Equivalent Number (PREN) of 43. The material carries EN10204-3.1B certification and meets NACE MR0175/ISO 15156-3 requirements for sour gas environments.
At room temperature, Super Duplex 2507 exhibits the following minimum mechanical properties:
Tensile strength Rm N/mm² | Yield strength RP0.2 N/mm² | Elongation rate A5% | Brinell hardness HB |
800 | 550 | 15 | 310 |
The material maintains structural integrity within an operating temperature range of -50°C to 300°C and demonstrates resistance to chloride-induced stress corrosion cracking in concentrations up to 20,000 ppm Cl⁻.
Parameter | Specification |
Standard | DIN1587 |
Size Range | M5-M64 or non-standard as requested |
Material | Duplex 2507, UNS S32750, F53, 1.4410 |
Grade | Grade 80 |
Finish | Bright and clean |
Marking | HT and FST or customization |
Certificates | EN10204-3.1B |
Non-standards | OEM available, according to drawings or samples |
The domed cap design incorporates a rounded top with a radius measuring 1.5× thread diameter, covering exposed bolt threads completely. Thread profiles conform to ISO 965-1 for metric sizes and ASME B1.1 for imperial sizes, with Class 2B fit tolerance.
These fasteners secure riser connections, subsea valve assemblies, and platform structural components exposed to continuous seawater contact and H2S/CO2 environments. The material withstands pressures up to 1000 bar in properly tensioned flange connections.
In chlor-alkali production plants, pulp and paper mills, and fertilizer manufacturing operations, the nuts resist corrosion from bleaching agents and ammonium sulfate solutions. They maintain dimensional stability during repeated thermal cycling processes.
Within flue gas desulfurization (FGD) systems and geothermal power plants, the fasteners endure high-chloride steam and acidic condensate exposure. They are used in cooling tower construction, with installation references in power facilities across India, Oman, Bangladesh, Israel, and Mexico.
For bridge construction, port infrastructure, and coastal buildings in salt-laden atmospheres, the nuts provide consistent performance without periodic replacement requirements.
The domed cap covers exposed bolt threads, preventing mechanical damage during handling and installation. It also eliminates flat surfaces where moisture and debris could accumulate.
Installation with dissimilar metals requires non-conductive washers to prevent galvanic corrosion. Optimal performance occurs when paired with bolts manufactured from identical Super Duplex 2507 material.
In properly torqued flange connections tensioned to 10-15% below yield strength, the nuts maintain integrity at pressures up to 1000 bar (14,500 PSI).
Super Duplex 2507 meets NACE MR0175/ISO 15156-3 requirements for H2S environments at temperatures up to 150°C with 3.5% NaCl content.
The material maintains impact toughness down to -40°C. Installation in sub-zero conditions requires proper lubrication during torque application.
Samples are available for evaluation, with packaging provided in bulk boxes within cartons on pallets, or configured according to customer specifications. Custom non-standard dimensions are produced from customer-provided drawings or sample components.
