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NAS 185N (UNS S31254) - Super Austenitic Stainless Steel

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 NAS 185N (UNS S31254) - Super Austenitic Stainless Steel

NAS 185N (SUS 312L, UNS S31254) is a high corrosion resistant austenitic stainless steel with a high nickel, high chromium, high molybdenum alloy design,
and provides excellent corrosion resistance in severe corrosion environments such as high temperature seawater. Depending on the environment,
this stainless steel offers high economy combined with corrosion resistance comparable to that of Nickel alloy and pure titanium. Nippon Yakin supplies this product in plate, sheet and strip form.

  • Image: Coil
  • Image: Sheet
  • Image: Plate


The hot and cold workability of NAS 185N is basically the same as that of standard austenitic stainless steels
such as Type 304, Type 316, etc. However, the fact that this is a high strength material must be considered in both cold and hot working.


Various welding methods are applicable in the same manner as with the standard austenitic stainless steels, including shielded metal arc welding, TIG welding,
and plasma welding. Alloy 276 welding consumable should be used.


As a feature of high Ni stainless steels, although machining is difficult in comparison with the standard austenitic stainless steels, it is easier than with Ni-based alloys.
A ultrahard tool should be used in machining if at all possible. It is also advisable to use a slower feed rate and deeper cutting depth.

Heat Treatment

Solution annealing of NAS 185N should be performed at 1150℃ and higher followed by being quenched in water or rapidly cooled by other means. (Conditions provided in ASTM A480/A480M)


A mixture of nitric acid and hydrofluoric acid is used in pickling. However, due to the high corrosion resistance of NAS 185N, scale is somewhat difficult to remove
in comparison with Type 304. Therefore, the material should be immersed in an alkaline solution before pickling, or if possible, shot blasting is extremely effective.


  • Seawater environments: Marine structures, seawater desalination systems, heat exchangers using seawater, condenser tubes, etc.
  • Pulp and paper plants: Various types of bleaching systems, scrubbers, etc.
  • Medical and pharmaceutical product plants: Centrifugal separators, reaction tanks, etc.


It is possible to manufacture UNS S31254 in accordance with the NORSOK standard below. The thickness is up to 40mm.

  • NORSOK M-650
  • NORSOK M-630 MDS R15