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Bumax Capscrews - The Strongest Stainless Steel Fastener

Bumax Capscrews - The Strongest Stainless Steel Fastener

Bumax Capscrews - The Strongest Stainless Steel Fastener

Last Updated: 16/2/24 at 8:52am


Bumax Stainless Steel Capscrew

What is the world’s strongest stainless steel fastener?

Bumax SDX109 fasteners are made from UNS S32750 stainless steel (Super Duplex 2507) and made to a tensile strength of 1000 MPa.

But an even stronger fastener is the Bumax DX129 stainless fastener range which are made from UNS S32205 stainless steel (Duplex 2205) and made to a tensile strength of an incredible 1200 MPa.

How does this compare in strength to other stainless steel fasteners?

As per fastener strength comparison guides, unmarked metric stainless steel fasteners are considered to have a minimum tensile strength of 500 MPa, however most are made to a tensile strength of 700 MPa (as marked A2-70 or A4-70) and some to a tensile strength of 800 MPa (A4-80). Bumax 109 is a version of 316 stainless steel made to a tensile strength of 1000 MPa (the same as the Super Duplex Bumax SDX109 version) but Bumax Duplex DX129 is made to an incredible tensile strength of 1200 MPa.

What are the features of Bumax SDX109 and Bumax DX129?

BUMAX SDX 109 is a high strength super duplex stainless steel fastener with excellent mechanical properties, and exceptional resistance to general crevice, pitting and stress corrosion in aggressive environments.

Typical applications for BUMAX® SDX 109 include heat exchangers in refineries, injection and ballast water systems, petrochemical industries, offshore platforms and power industries.


  • UNS S32760: EN 1.4501
  • UNS S32750: EN 1.4410


  • Excellent resistance– to general corrosion, pitting and crevice corrosion and chloride induced Stress Corrosion Cracking.
  • Lower thermal expansion coefficient– compared to austenitic stainless steels.
  • High strength – up to strength class 12.9.
  • Excellent ductility.
  • Delivery: 2 weeks from Sweden (subject to availability)
  • Excellent fatigue properties.

BUMAX DX 129 is a Duplex Stainless Steel Capscrew that combines strength, corrosion resistance and ductility for the most demanding environments.


  • UNS S32205
  • EN 1.4462


  • Corrosion resistance: significantly better than 316
  • Tensile strength: min 1200 MPa (Class 70 316 has a tensile strength of 700 MPa)
  • Yield strength: min 1080 MPa.
  • Elongation: significantly better than 12.9 carbon steel.
  • Delivery: 2 weeks from Sweden (subject to availability)
  • Sizes: M6–M16 available.

Always select which grade of stainless steel is appropriate for the application and be sure to follow good stainless steel guidelines. For help and advice on stainless steel grade selection, please contact the Nickel Institute or the Australian Stainless Steel Development Association.

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