50 grades of stainless steel

The BSSA has selected 50 Grades of Stainless Steel as its theme for 2014. Each week throughout the year, we will showcase one grade and illustrate the variety of corrosion resistant, mechanical and physical properties which determine its suitability for a wide range of applications.



Superduplex 1.4410/1.4501/1.4507 S32750/S32760/S32550

Cable Protection Fasteners

Cable Protection Fasteners

Courtesy of West Special Fasteners

Filtration Screens from Wedge Wire

Filtration Screens from Wedge Wire

Courtesy of Hempel Wire

Superduplex is a generic term covering a range of highly alloyed grades developed for use in highly aggressive conditions, notably in sea water.

Approximate Composition – 25% Cr 7% Ni 3.5% Mo 0.25% N (nitrogen) plus optional Cu (copper) and W (tungsten). (Exact composition ranges vary between EN and ASTM standards).

This grade combines the following characteristics:

  • Excellent pitting and crevice corrosion resistance (PREN > 40)
  • Excellent stress corrosion cracking resistance
  • Good yield strength (550 MPa minimum)
  • Good impact toughness down to minus 50°C
  • Cu bearing grades excellent resistance to sulphuric acid
  • Knowledge required to maintain properties in fabrication

The superduplex grades are used in extremely aggressive conditions notably in seawater and high chloride or acidic chemical processes. Their complex metallurgy means that the process parameters must be kept within narrow ranges to maintain the required microstructure, corrosion resistance and impact toughness. This is especially true in welding. Therefore, fabricators require relevant training and approvals to work effectively with this material.

Applications include:

Oil and gas subsea, desalination, chemical processing, pulp and paper, valves, pumps, fish stunning electrodes, firewater systems.

Superduplex grades provide a combination of high corrosion resistance and strength in very aggressive conditions.

Find out more about the 50 Grades of Stainless Steel campaign

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British Stainless Steel Association (BSSA): registered in England and Wales as a private company limited by guarantee; registration no. 07547349


Superduplex 1.4410/1.4501/1.4507 S32750/S32760/S32550