• Alloy 255
  • 1.4507
  • Norsok MDS D54
  • UNS S32550 (Super Duplex 32550)
View Data Tables For This Product

Ferralium 255 – 3SF for Forgings (UNS S32550)

Ferralium® 255 – 3SF is a super duplex stainless steel supplied as forgings. As a 25% Cr alloy, with significant additions of Cu, it offers excellent corrosion resistance in a variety of corrosive chemicals including, but not limited to, sulphuric, nitric and phosphoric acid.

In seawater and other chloride contaminated environments it also provides outstanding resistance to pitting and crevice corrosion, with a critical pitting temperature exceeding 50°C.

Excellent ductility and impact strength at both ambient and sub-zero temperatures combine with a high resistance to abrasion, erosion and cavitation erosion.

stainless steels


  • Alloy 255
  • 1.4507
  • Norsok MDS D54
  • UNS S32550 (Super Duplex 32550)
View Data Tables For This Product

Data Tables

Chemical Composition:


Mechanical Properties:

0.2% Proof Stress550 N/mm279.8 ksi
Tensile Strength750 N/mm2108.8 ksi
Elongation, 5.65√S0 and 4D25%
Reduction of Area
Hardness (Brinell)220 - 270
Impact Strength (Room Temp)80J59.0 ft.lb


  1. Testing shall be carried out in accordance with ASTM A370 or EN ISO 6892-1 (tensile), EN ISO 6506-1 (hardness)
  2. Minimum properties quoted (tested at room temperature in a longitudinal direction)
  3. Testing performed on each melt of material per heat treatment batch
  4. Hardness shall be in accordance with NACE MR 1075 with a maximum HRC value of 28 (270HB)
  5. ASTM G48A corrosion test (at 50°C)  no pitting and < 0.8g/m2 weight loss
  6. Ferrite content  35-55%
  7. Microstructure certified free from grain boundary carbides, sigma, chi and laves phases





Physical Properties:

Density (Kg/m3)7810
Magnetic Permeability (20°C)33
Young’s Modulus (kN/mm2)199
Specific Electrical Resistance, 20°C (µΩ-m)0.8
Mean coefficient of thermal expansion, 20-100°C (m/m/degC)11.1 x 10-6
Specific Heat, 20°C (J/kg.K)475
Thermal conductivity, 20°C (W/m.K)14.2
Fracture Toughness, KQ (MPa/m2)98

Product Features

Key Features:

  • Particularly suitable for larger components as the formation of sigma phase is much less likely than it is for other Super Duplexes
  • Ferralium® was originally developed in 1960’s, pioneering the addition of nitrogen, to create the first super duplex stainless steel
  • Continuously developed through 1990’s to extend PREN > 40, and more recently to increase mechanical properties
  • Pitting Resistance Equivalent (PREN) >40, indicating outstanding resistance to pitting and crevice corrosion
  • Higher copper content provides self-healing effect at sites of pitting to inhibit further growth
  • Available as bars, plate, pipe and fittings with complementary weld wire
  • Listed in NACE MR 0175 for sour service


  • Oil & Gas industry pumps, valves, wellhead and subsea equipment
  • Pollution control scrubbers, precipitators, fans and pumps
  • Marine propellers, shafts, rudders, seals, pumps, valves
  • Bolts and fasteners
  • Process industry equipment in sulphuric acid, nitric acid, phosphoric acid, PP / PVC/TiOx production, agrochemicals
  • Grain and vegetable processing plant, sugar cane centrifuges
  • Pulp and paper digester blow vales, feed valves, washers, black liquor heater tubes, bleaching components
  • Copper smelting fans, tuyere bars, wet scrubbers, leaching area precipitators
  • Water and sewage treatment, desalination, swimming pools
Datasheet SD Ferralium 255 3SF Forgings Brochure Ferralium 255 SD50 detailed product information (rev2)
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