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Installation/Set-Up Challenges for Duplex Fasteners

Duplex fasteners, which are made from duplex stainless steel that combines features of both austenitic and ferritic stainless steels, are known for their corrosion resistance and strength. However, some common installation or setup challenges when using duplex fasteners include:

  1. Galling: Duplex stainless steel fasteners have a tendency to gall, which is the process where the bolt and nut seize together during tightening due to friction. To mitigate this issue, lubricants or anti-galling coatings can be used during installation.

  2. Work Hardening: Duplex stainless steel can work harden when forming threads during installation, leading to increased hardness and potential brittleness. Care should be taken to use the appropriate tools and techniques to prevent work hardening.

  3. Hydrogen Embrittlement: During the manufacturing process or service conditions, duplex fasteners can be exposed to hydrogen, leading to hydrogen embrittlement which can reduce the material's toughness. Proper heat treatment and handling procedures should be followed to minimize the risk of hydrogen embrittlement.

  4. Differential Thermal Expansion: Due to the dual-phase microstructure of duplex stainless steel, differential thermal expansion between the austenite and ferrite phases can occur during temperature changes. This can result in stress accumulation and potential joint failure. Design considerations should account for thermal expansion differences to prevent issues.

  5. Optimal Torque and Tension: Achieving the correct torque and tension is crucial when installing duplex fasteners to ensure proper clamping force and structural integrity. Using calibrated torque tools and following manufacturer guidelines for tightening procedures is essential.

  6. Corrosion Protection: While duplex stainless steel is highly corrosion-resistant, proper installation techniques and surface finishes should be employed to avoid contaminant entrapment which can lead to localized corrosion issues.

By addressing these common challenges with proper installation techniques, tools, and maintenance practices, the performance and longevity of duplex fasteners can be maximized.