Ferralium 255 – SD50 (UNS S32550)

Description:

Ferralium® 255 – SD50 is a super duplex stainless steel supplied in the hot worked and annealed condition. It achieves higher strengths than most other stainless steels and alternative corrosion resistant alloys, offering the potential to reduce section size and therefore weight and cost.

As a 25% Cr alloy, with significant additions of copper, it offers 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 at both ambient and sub-zero temperatures combine 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-SD50 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:

  • 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
  • First super duplex stainless steel to achieve 586N/mm2 as a minimum 0.2% Proof Stress, up to 12” (300mm) section sizes
  • 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 Duplex grades

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 0.025 1.20 0.25 0.70 0.025 0.005 Balance

Mechanical Properties:

Bars up to and including 4.0” (100mm) diameter or section Bars greater than 4.0” (100mm) and up to 12.0” (300mm) diameter or section Bars greater than 12.0” (300mm) diameter or section
0.2% Proof Stress 586 N/mm2 85ksi 586 N/mm2 85ksi 570 N/mm2 83ksi
Tensile Strength 790 N/mm2 114.5ksi 790 N/mm2 114.5ksi 760 N/mm2 110ksi
Elongation, 5.65√S0 and 4D 25% 25% 25%
Reduction of Area 50% 50% 50%
Hardness (Brinell) 220-270 220-270 220-270
Impact Strength (Room Temp) 80J 59 ft.lb 80J 59 ft.lb 80J 59 ft.lb
Impact Strength (-46degC) 45J av (35J min) 33 ft.lb av (25.8 ft.lb min) 45J av (35J min) 33 ft.lb av (25.8 ft.lb min) 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. 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 (Ω-m) 0.80 x 10-6
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

Downloads

Datasheet - SD-Ferralium 255 SD50 Bar

Datasheet - SD-Ferralium 255 SD50 Bar

Brochure - Ferralium 255-SD50 - Detailed product information

Brochure - Ferralium 255-SD50 - Detailed product information

Brochure - Ferralium 255-SD50 - Machining Guidelines

Brochure - Ferralium 255-SD50 - Machining Guidelines

Brochure - Ferralium 255-SD50 - Welding Guidelines

Brochure - Ferralium 255-SD50 - Welding Guidelines

Brochure - Ferralium 255, The reliable alloy choice for acid production processes

Brochure - Ferralium 255, The reliable alloy choice for acid production processes