Duplex Bolts

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Duplex Bolts
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Introduction to Duplex Bolts

• Duplex fasteners are made from austenitic-ferritic
  stainless steels that contain equal proportions
  of austenite and ferrite, resulting in superior
  mechanical strength and enhanced corrosion
  resistance. This unique composition makes duplex
  fasteners ideal for demanding applications in
  industries such as petrochemical, offshore, and
  construction, where high strength and resistance
  to stress corrosion cracking are crucial.

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Types of Duplex Bolts

• DSS J-Bolts

• Duplex Hex Bolts

• J-bolts are used for anchoring and fastening in
  concrete, providing stability and support in
  construction projects.

• Hex bolts made of duplex stainless steel are
  known for their high strength and corrosion
  resistance, ideal for structural applications.

• Duplex Friction Grip Bolts

• Duplex U-Bolts

• These bolts are designed to provide an enhanced
  grip in high-stress applications, reducing the
  risk of loosening due to vibrations.

• U-bolts feature a U-shaped design and are
  commonly used to secure pipes and other
  cylindrical objects in place.

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Specifications and Standards

• Sizes

• Grades

• Temperature Ranges

• Duplex fasteners are available in various sizes
  including imperial (1/4" to 4") and metric (M1.2
  to M48) with lengths ranging from 12mm to 1200mm.

• Common grades of duplex fasteners include Duplex
  2205, ASTM A182 F51, and ASTM A182 F60, each
  providing specific mechanical properties and
  corrosion resistance.

• Duplex fasteners are suitable for temperature
  ranges between -50 C to 300 C, making them
  versatile for different industrial applications.

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Chemical and Mechanical Properties

• Chemical Composition

• Duplex stainless steel typically contains 19-28
  chromium for corrosion resistance.
• Nickel content ranges from 4.5-8 which enhances
  toughness and ductility.
• Molybdenum is present in 2-3 to improve
  resistance to pitting and crevice corrosion.
• Typical grades include UNS S31803 and S32205 with
  specific elemental limits defined.

• Mechanical Properties

• Yield strength for Duplex 2205 is around 448 MPa,
  offering superior strength.
• Tensile strength can reach up to 650-880 MPa,
  making them suitable for high-stress
  applications.
• Elongation percentage is about 25 in 50mm,
  indicating good ductility.
• These fasteners exhibit excellent resistance to
  stress corrosion cracking, enhancing reliability.

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Comparing Duplex Eye and U Bolts

• Duplex Eye Bolts

• Duplex U Bolts

• Feature a loop at one end, allowing for easy
  attachment of a hook or rope, making them ideal
  for lifting applications.
• Provide versatility for connecting to a single
  point, often used in rigging and anchoring
  scenarios.
• Available in various sizes and grades,
  accommodating different load capacities and
  environmental conditions.

• Require a nut on each end for secure fastening,
  which may complicate installation in tight
  spaces.
• Primarily designed for specific applications,
  often limiting their versatility compared to eye
  bolts.
• May not be suitable for applications requiring
  quick attachment or detachment due to their
  threaded design.

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Conclusion

• Duplex Bolts are essential components in various
  industries due to their superior mechanical
  strength and excellent corrosion resistance.
  Their unique austenitic-ferritic structure allows
  them to withstand harsh environments, making them
  ideal for applications in petrochemical plants,
  offshore structures, and automotive industries.
  Understanding the specifications and diverse
  types of duplex fasteners enables engineers and
  procurement professionals to select the right
  fasteners for their specific applications,
  enhancing safety and durability in construction
  and manufacturing.