What is Ferralium 255?

Ferralium 255 (UNS S32550, EN 1.4507, X2CrNiMoCuN25-6-3) is a Cu-bearing super duplex stainless steel with nominal composition 25Cr-5Ni-3Mo-2Cu-0.2N. PREN >= 40, balanced austenite-ferrite microstructure (35-55% ferrite per NORSOK M-630), supplied solution-annealed (no precipitation hardening). Critical Pitting Temperature >= 35 °C per ASTM G48 method A. Used in seawater service, oil & gas downhole, subsea, desalination and chemical processing. Ferralium is a registered trademark of Langley Alloys.

How does Ferralium 255 chemical composition differ from Duplex 2205 chemical composition?

Ferralium 255 (UNS S32550) chemistry: Cr 24-27%, Ni 4.5-6.5%, Mo 2.9-3.9%, Cu 1.5-2.5%, N 0.10-0.25%, balance Fe. Duplex 2205 (UNS S31803/S32205) chemistry: Cr 21-23%, Ni 4.5-6.5%, Mo 2.5-3.5%, N 0.08-0.20%, no Cu. Ferralium 255 has higher Cr, higher Mo, higher N, plus 2% Cu — pushing PREN from ~35 (Duplex 2205) to ~40+ (super duplex threshold).

What is PREN and why is Ferralium 255 super duplex?

PREN (Pitting Resistance Equivalent Number) = %Cr + 3.3 · %Mo + 16 · %N. With nominal 25 Cr, 3 Mo, 0.2 N, Ferralium 255 PREN = 25 + 9.9 + 3.2 = 38.1 minimum, typically 40-42 per heat. PREN >= 40 is the threshold defining super duplex stainless steel grades, distinguishing Ferralium 255 from standard duplex grades like Duplex 2205 (PREN ~35).

What super duplex stainless steel grades exist alongside Ferralium 255?

The commercially significant super duplex stainless steel grades are: Ferralium 255 (UNS S32550, Cu-bearing, EN 1.4507), Super Duplex 2507 (UNS S32750, no Cu, EN 1.4410, slightly higher Cr/Mo), and Zeron 100 (UNS S32760, W-bearing, EN 1.4501). All have PREN >= 40. Standard duplex grades like Duplex 2205 (UNS S31803/S32205, EN 1.4462, PREN ~35) sit below the super duplex threshold.

Which super duplex stainless steel ASTM grades cover Ferralium 255?

ASTM A479 (bar/billet/shapes), ASTM A789 (seamless/welded tube), ASTM A790 (seamless/welded pipe), ASTM A815 (wrought fittings), ASTM A182 (forged flanges/fittings/valves), ASTM A276 (bars/shapes alternative). All under UNS S32550 designation. EN equivalents: EN 10088-3, EN 10222-5, EN 10272.

Is Ferralium 255 NORSOK M-650 qualified?

Ferralium 255 can be supplied with NORSOK M-650 Qualification Test Records (QTR) demonstrating manufacturer qualification per NORSOK M-630 material data sheet MDS D55. The QTR documents heat treatment, ferrite content (35-55% base, 35-65% weld), Charpy >= 45 J at -46 °C, Critical Pitting Temperature per ASTM G48 method A, and microstructural verification. Required for North Sea, Norway and high-criticality offshore projects.

Is Ferralium 255 NACE MR0175 / ISO 15156 compliant for sour service?

Yes. Ferralium 255 is qualified under NACE MR0175 / ISO 15156-3 for sour service when supplied solution-annealed with hardness <= 32 HRC and ferrite content 35-55% per NORSOK M-630. TorqBolt provides per-heat MTC (EN 10204 type 3.2) certifying NACE MR0175 compliance for downhole, wellhead and sour-gas applications.

Where can I buy Ferralium 255 in India?

TorqBolt Pvt Ltd manufactures Ferralium 255 at facilities in Mumbai and Rajkot, India. Bar, plate, sheet, pipe, tube, fittings, flanges, forgings, hex bolts, stud bolts, hex nuts and threaded rod available with per-heat MTC (EN 10204 type 3.2) and optional NORSOK M-650 QTR + NACE MR0175 documentation. Contact info@torqbolt.com or +91-22-66157017.

Duplex Stainless Steel: UNS S31803 / S32205 (Duplex 2205)

Name: Ferralium 255 (UNS S32550), Cu-bearing Super Duplex Stainless Steel
Brand: TorqBolt

Duplex Stainless Steel: UNS S31803 / S32205 (Duplex 2205) Reference

Duplex stainless steel is the family of two-phase (austenite + ferrite) stainless steels with balanced microstructure, typically 35–55% ferrite per NORSOK M-630. The most-specified standard duplex grade is Duplex 2205 (UNS S31803 / S32205). Super-duplex grades like Ferralium 255 (UNS S32550) extend the corrosion-resistance envelope above Duplex 2205 limits via higher Cr / Mo / N and Cu addition.

Duplex 2205 (UNS S31803 / S32205): The Standard Duplex Grade

Composition: Cr 22%, Ni 5%, Mo 3%, N 0.15%. PREN ~35. EN designation 1.4462 / X2CrNiMoN22-5-3. Original UNS S31803 specification (1980s) permitted wider Cr / Mo / N ranges; modern UNS S32205 (1996+) narrowed these to guarantee PREN ≥ 35 per heat. Most current mill heats are dual-certified S31803 / S32205 by hitting the narrower S32205 ranges.

Duplex 2205 Chemical Composition

Element	UNS S31803	UNS S32205
Carbon (C), max.	0.030	0.030
Chromium (Cr)	21.0–23.0	22.0–23.0
Nickel (Ni)	4.5–6.5	4.5–6.5
Molybdenum (Mo)	2.5–3.5	3.0–3.5
Nitrogen (N)	0.08–0.20	0.14–0.20
Manganese (Mn), max.	2.00	2.00
Sulphur (S), max.	0.020	0.020
Phosphorus (P), max.	0.030	0.030

Element

UNS S31803

UNS S32205

Carbon (C), max.

0.030

Chromium (Cr)

21.0–23.0

22.0–23.0

Nickel (Ni)

4.5–6.5

Molybdenum (Mo)

2.5–3.5

3.0–3.5

Nitrogen (N)

0.08–0.20

0.14–0.20

Manganese (Mn), max.

2.00

Sulphur (S), max.

0.020

Phosphorus (P), max.

0.030

Duplex 2205 Mechanical Properties

Property	Minimum (Duplex 2205)
Yield strength (Rp0.2)	450 MPa (65 ksi)
Tensile strength (Rm)	620 MPa (90 ksi)
Elongation (A5)	25%
Hardness, max	32 HRC (NACE MR0175)
Density	7.80 g/cm³
Charpy at –46 °C, min (NORSOK)	45 J

Property

Minimum (Duplex 2205)

Yield strength (Rp0.2)

450 MPa (65 ksi)

Tensile strength (Rm)

620 MPa (90 ksi)

Elongation (A5)

25%

Hardness, max

32 HRC (NACE MR0175)

Density

7.80 g/cm³

Charpy at –46 °C, min (NORSOK)

45 J

Duplex 2205 vs Super Duplex Grades

ASTM Specifications for Duplex 2205

Bar: ASTM A479 (UNS S31803, S32205). Plate / sheet: ASTM A240. Pipe: ASTM A790. Tube: ASTM A789. Fittings: ASTM A815. Forgings: ASTM A182 (grade F51 for S31803, F60 for S32205). EN equivalents: EN 10088-3 (1.4462), EN 10222-5 (forgings), EN 10272 (pressure-rated bar). NORSOK M-630 material data sheet MDS D45.

Passivation (ASTM A967)
Pickling (ASTM A380)
Electropolishing
Mill / 2B / 2D / BA finish
Bright bar / centreless ground
Peeled & polished bar
Shot-blast (EN 10088-2)

ISO 9001:2015
NORSOK M-650
NACE MR0175
ISO 15156-3
PED 2014/68/EC
EN 10204 type 3.2
AD 2000 W2/W7/W10

Duplex Stainless Steel: UNS S31803 / S32205 (Duplex 2205) Reference

Duplex 2205 (UNS S31803 / S32205): The Standard Duplex Grade

Duplex 2205 Chemical Composition

Duplex 2205 Mechanical Properties

Duplex 2205 vs Super Duplex Grades

ASTM Specifications for Duplex 2205

Specifications

Surface Finish

Certifications

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