Ferralium 255 – 3AF Aged Grade (UNS S32550)

Description:

Ferralium® 255 – 3AF is a super duplex stainless steel supplied in the hot worked, annealed and aged condition. By subjecting the product to an additional ageing process, it is possible to further increase the tensile strength of the product whilst retaining high levels of ductility. As a variant of our unique Ferralium® 255 – SD50 product, it is a 25% Cr alloy with significant additions of Cu, offering excellent corrosion resistance in a wide variety of corrosive chemicals including sulphuric, nitric and phosphoric acid.  In seawater and other chloride containing environments it also provides outstanding resistance to pitting and crevice corrosion, with Critical Pitting Temperature exceeding 50°C.

Excellent ductility and impact strength are retained 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. Listed in NACE MR 01 75 for sour service and having gained ASME Approval for Pressure Vessel applications, Ferralium® 255-3AF 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.

Key Features:

  • Aged product achieves even higher tensile strength, > 840N/mm2 (121.8 ksi), whilst retaining high ductility
  • 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
  • Very low levels of sulphur minimise the likelihood of inclusions as sites for potential pitting 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
  • Particularly suitable for larger components as the formation of sigma phase is much less likely than it is for other Super Duplexes

Applications:

  • 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

Chemical Composition:

Cr Ni Mo Co Nb (+Ta) Ti V W Cu C Mn N Si P S Fe Al
Min 24.50 5.50 3.10 1.50 0.80 0.20
Max 26.50 6.50 3.80 2.00 0.03 1.20 0.25 0.70 0.025 0.005 Balance

Mechanical Properties:

0.2% Proof Stress 600 N/mm2 87 ksi
Tensile Strength 840 N/mm2 121.8 ksi
Elongation, 5.65√S0 and 4D 23%
Reduction of Area
Hardness (Brinell) 250-330
Impact Strength (Room Temp) 70J 51.6 ft.lb

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. Hardness shall be in accordance with NACE MR 1075 with a maximum HRC value of 28 (270HB)
  5. ASTM A262 corrosion test (Practice B) no pitting and < 0.54g/m2hr 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) 200
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

Downloads

Datasheet - SD-Ferralium 255 3AF Aged

Datasheet - SD-Ferralium 255 3AF Aged

Brochure - Ferralium 255-SD50 - detailed product information (rev2)

Brochure - Ferralium 255-SD50 - detailed product information (rev2)

Brochure - Ferralium 255-SD50 - Machining Guidelines

Brochure - Ferralium 255-SD50 - Machining Guidelines

Brochure - Ferralium 255-SD50 - Welding Guidelines

Brochure - Ferralium 255-SD50 - Welding Guidelines