UNS S32550 welded tubes and pipes are ideal for applications where you need a combination of super duplex strength and increased resistance to sulfuric acid and abrasive conditions. Known as Ferralium 255 or Alloy 255, this grade consists of 24-27% chromium, 2.9-3.9% molybdenum and 1.5-2.5% copper. Importantly, the high content of copper makes it possible for UNS S32550 to resist sulfuric acid and wear due to abrasive slurries. Amardeep Steel supplies welded pipes and tubes according to ASTM A789, A790 and A928 specifications, ensuring the highest quality product. See our Ferralium 255 round bars, compare UNS S32520 welded pipes and tubes, or browse all super duplex steel pipes and tubes. Every order includes an EN 10204 3.1 mill test certificate and full heat traceability.
What Are UNS S32550 Welded Pipes and Tubes?
S32550 was one of the first super duplex stainless steels. It combines a 550 MPa minimum yield with good resistance to chloride pitting, chloride stress corrosion cracking, sulfuric acid and erosion corrosion. It is used where both acid attack and wear are a problem, such as phosphoric acid slurries and scrubber systems. Service is generally kept below about 300°C.
Welding S32550
S32550 is welded with matching or over alloyed duplex filler and nitrogen bearing shielding gas to hold the austenite and ferrite balance in the seam. Welded pipe and tube are solution annealed and rapidly cooled after welding, as ASTM A789 and A790 require. Large bores are supplied as EFW pipe to ASTM A928; confirm the grade listing in the edition on your order.
S32550 Welded Pipe Specifications
Parameter | Details |
|---|---|
Grade | Super Duplex S32550 (Ferralium 255) |
UNS | S32550 |
Standards | ASTM A789 / ASME SA789 (tube), ASTM A790 / ASME SA790 (pipe), ASTM A928 (EFW pipe) |
Type | Welded tube and pipe, longitudinal seam, TIG or plasma welded; larger bores as EFW pipe with filler |
Size Range | Tube and pipe sizes to the purchase specification |
Schedules | SCH 5S, 10S, 40S, 80S and specified wall |
Length | Random, fixed and cut lengths |
Ends | Plain end and bevelled end |
Heat Treatment | Solution annealed and rapidly cooled after welding |
Test Certificate | EN 10204 3.1, with 3.2 available on request |
S32550 Chemical Composition
Element | Content (%) |
|---|---|
Carbon (C) | 0.04 max |
Manganese (Mn) | 1.50 max |
Phosphorus (P) | 0.040 max |
Sulfur (S) | 0.030 max |
Silicon (Si) | 1.00 max |
Nickel (Ni) | 4.5 to 6.5 |
Chromium (Cr) | 24.0 to 27.0 |
Molybdenum (Mo) | 2.9 to 3.9 |
Nitrogen (N) | 0.10 to 0.25 |
Copper (Cu) | 1.50 to 2.50 |
Limits are per ASTM A790. S32550 allows slightly more carbon (0.04%) than most other super duplex grades (0.030%).
S32550 Mechanical Properties
Property | Value |
|---|---|
Tensile Strength, min | 760 MPa (110 ksi) |
Yield Strength (0.2% offset), min | 550 MPa (80 ksi) |
Elongation in 50 mm, min | 15% |
Hardness, max | 297 HBW / 31 HRC |
S32550 Equivalent Grades
Standard | Designation |
|---|---|
UNS | S32550 |
Common name | Ferralium 255, Alloy 255 |
Closest EN grade | 1.4507 (X2CrNiMoCuN25-6-3), a close match, not identical |
ASTM pipe / tube | A790 / A789 / A928 |
EN 1.4507 is also matched to UNS S32520. Treat it as a close match for S32550 and check the drawing before switching standards.
S32550 Welded Pipe Size and Weight Chart
NPS | OD (mm) | SCH 10S wall / weight | SCH 40S wall / weight |
|---|---|---|---|
1/2" | 21.34 | 2.11 mm / 1.00 kg/m | 2.77 mm / 1.26 kg/m |
3/4" | 26.67 | 2.11 mm / 1.27 kg/m | 2.87 mm / 1.68 kg/m |
1" | 33.40 | 2.77 mm / 2.08 kg/m | 3.38 mm / 2.49 kg/m |
1 1/2" | 48.26 | 2.77 mm / 3.09 kg/m | 3.68 mm / 4.03 kg/m |
2" | 60.33 | 2.77 mm / 3.91 kg/m | 3.91 mm / 5.41 kg/m |
3" | 88.90 | 3.05 mm / 6.42 kg/m | 5.49 mm / 11.24 kg/m |
4" | 114.30 | 3.05 mm / 8.33 kg/m | 6.02 mm / 15.99 kg/m |
6" | 168.28 | 3.40 mm / 13.75 kg/m | 7.11 mm / 28.12 kg/m |
8" | 219.08 | 3.76 mm / 19.86 kg/m | 8.18 mm / 42.33 kg/m |
Wall thickness to ASME B36.19. Weights in kg/m, worked out as (OD minus wall) x wall x π x 7.81 / 1000. Heavier schedules and specified walls on request.
S32550 vs S32520 vs S32750
Property | S32550 | S32520 | S32750 |
|---|---|---|---|
Chromium | 24.0 to 27.0% | 24.0 to 26.0% | 24.0 to 26.0% |
Molybdenum | 2.9 to 3.9% | 3.0 to 4.0% | 3.0 to 5.0% |
Nitrogen | 0.10 to 0.25% | 0.20 to 0.35% | 0.24 to 0.32% |
Copper | 1.50 to 2.50% | 0.50 to 2.00% | 0.50% max |
Min. tensile / yield | 760 / 550 MPa | 770 / 550 MPa | 800 / 550 MPa |
Min. elongation | 15% | 25% | 15% |
PREN (spec range) | 35.2 to 43.9 | 37.1 to 44.8 | 37.7 to 47.6 |
PREN is worked out as Cr + 3.3 Mo + 16 N, using the minimum and maximum of each specified range. Strength values are ASTM A790 minimums.
For more nitrogen and a higher minimum PREN, see our UNS S32520 welded pipes and tubes. For seamless super duplex in seawater, see our UNS S32750 and S32760 super duplex pipes.
Applications of S32550 Welded Pipes and Tubes
- Sulfuric and phosphoric acid plant piping
- Abrasive slurry lines in mining and fertilizer plants
- Flue gas scrubber and FGD systems
- Offshore seawater and produced water lines
- Pulp and paper bleach plant piping
Testing and Documentation
Every order of S32550 welded pipe and tube goes through the checks below at our testing facility or approved third party labs.
- Chemical analysis and PMI
- Tension and hardness tests
- Flattening test, with flange test on tube
- Hydrostatic or eddy current test on every length
- Weld seam radiography for ASTM A928 classes that call for it
- ASTM G48 pitting test and ferrite content check on request
- Visual and dimensional inspection, including weld bead height
Mill test certificates are issued to EN 10204 3.1, with 3.2 available on request. You can view our approvals on the certificates page.
Packing and Marking
Each length is marked with the standard, UNS S32550, size, heat number and manufacturer name. Ends are capped, and pipes are kept apart from carbon steel and packed in bundles or wooden boxes. Read more about our packing and despatch process.
Request a Quote for UNS S32550 Welded Pipes & Tubes
Send us the OD or NB, wall or schedule, standard (A789, A790 or A928), length and quantity, and our team will reply with price and delivery. Use the enquiry form or reach us through the contact page.
Frequently Asked Questions
What is UNS S32550?
UNS S32550, known as Ferralium 255 or Alloy 255, is a super duplex stainless steel with 24% to 27% chromium, 4.5% to 6.5% nickel, 2.9% to 3.9% molybdenum, 0.10% to 0.25% nitrogen and 1.5% to 2.5% copper.
Is Ferralium 255 the same as UNS S32550?
Yes. Ferralium 255 is a trade name for alloy made to UNS S32550.
What are the mechanical properties of S32550 pipe?
ASTM A790 sets 760 MPa (110 ksi) minimum tensile strength, 550 MPa (80 ksi) minimum yield, 15% minimum elongation and 297 HBW maximum hardness.
Why does S32550 contain so much copper?
The 1.5% to 2.5% copper improves resistance to sulfuric acid and other reducing acids, and helps in erosion corrosion service such as acid slurries.
Which standards cover S32550 welded pipe?
ASTM A790 covers welded pipe, ASTM A789 covers welded tube and ASTM A928 covers electric fusion welded pipe.
