Specifications

  • Alloy 255
  • 1.4507
  • X2CrNiMoCuN 25-6-3
  • Z3 CNDU 25-07 Az
  • Norsok MDS D59
  • ASTM A276/A476
  • UNS S32550
  • ASME A182 F61
View Data Tables For This Product

Ferralium 255 – FG46 Fastener Grade (UNS S32550)

Ferralium® 255 – FG46 is a super duplex stainless steel which is supplied in the strain hardened condition (Condition S). It is optimised for fastener applications, matching the mechanical properties of the B7 grade alloy carbon steel which is most commonly used for high-pressure bolting applications.

As a variant of our unique Ferralium® 255 – SD50 product, it is a 25% Cr alloy with significant additions of Cu, delivering excellent corrosion resistance in a variety of corrosive chemicals including sulphuric, nitric and phosphoric acid.

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

The product retains its excellent ductility and impact strength at both ambient and sub-zero temperatures, despite the elevated strength levels. These are combined with a high resistance to abrasion, erosion and cavitation erosion.

Ferralium® 255-FG46 is tested to the highest degree using tests designed to guarantee that the trade-marked product possesses high integrity, a correct phase balance and the absence of sigma and other deleterious phases.

Ferrallium 255

Specifications

  • Alloy 255
  • 1.4507
  • X2CrNiMoCuN 25-6-3
  • Z3 CNDU 25-07 Az
  • Norsok MDS D59
  • ASTM A276/A476
  • UNS S32550
  • ASME A182 F61
View Data Tables For This Product

Data Tables

Chemical Composition:

CrNiMoCoNb (+Ta)TiVWCuCMnNSiPSFeAl
Min24.505.503.101.500.800.20
Max26.506.503.802.000.0251.200.250.700.0250.005Balance

Mechanical Properties:

Bars up to and including 4.0” diameter or section
0.2% Proof Stress720 N/mm2104.4 ksi
Tensile Strength860 N/mm2124.7 ksi
Elongation, 5.65√S0 and 4D16%
Reduction of Area50%
Hardness (Brinell)220-335
Impact Strength (Room Temp)80J59 ft.lb
Impact Strength (-46degC)45J av (35J min)33 ft.lb av (25.8 ft.lb min)

Notes:

  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. ASTM G48A corrosion test (at 50°C)  no pitting and < 0.8g/m2 weight loss
  5. Ferrite content  35-55%
  6. 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)220
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

Product Features

Key Features:

  • High Strength – the minimum 0.2% Proof Stress of 720 N/mm2 to match B7 carbon steel
  • Ferralium® was originally developed in 1960’s, pioneering the addition of nitrogen, to create the first super duplex stainless steel
  • Throughout the 1990’s, further developments were completed to extend PREN > 40, and more recently to increase its mechanical properties
  • Outstanding resistance to pitting and crevice corrosion in seawater and other chloride containing environments
  • Excellent corrosion resistance in a wide variety of corrosive chemicals including sulphuric, phosphoric and nitric acids
  • Excellent ductility and impact strength at both ambient and sub-zero temperatures
  • High resistance to abrasion, erosion and cavitation erosion
  • Excellent resistance to stress corrosion cracking in chloride containing environments
  • High structural integrity, optimised phase balance and the absence of sigma and other deleterious phases

Applications:

  • Ferralium® 255 – FG46 has been optimised for fastener applications, complementing where Ferralium® 255 – SD50 is routinely used
  • 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
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