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 2205 Properties: Mechanical, Physical, Corrosion

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

Duplex 2205 (UNS S31803 / S32205, EN 1.4462) is the most-specified standard duplex stainless steel grade. Properties are roughly twice as strong as 316L austenitic stainless at room temperature (yield 450 MPa vs 170 MPa for 316L), with comparable corrosion resistance to 317L and significantly better than 304/316L in chloride-bearing service. PREN ~35 places Duplex 2205 below the super-duplex threshold; for service beyond Duplex 2205 limits, super-duplex grades like Ferralium 255 are required.

Duplex 2205 Mechanical Properties

Property	Minimum	Standard
Yield strength (Rp0.2)	450 MPa (65 ksi)	ASTM E8
Ultimate tensile strength (Rm)	620 MPa (90 ksi)	ASTM E8
Elongation (A5)	25%	ASTM E8
Hardness (Brinell), max	293 HBW (~32 HRC NACE)	ASTM E10 / E18
Charpy V-notch impact at −46 °C, min	45 J (NORSOK M-630)	ASTM E23 / ISO 148-1
Density	7.80 g/cm³	none
Modulus of elasticity	200 GPa (29 × 10³ ksi)	none

Property

Minimum

Standard

Yield strength (Rp0.2)

450 MPa (65 ksi)

ASTM E8

Ultimate tensile strength (Rm)

620 MPa (90 ksi)

ASTM E8

Elongation (A5)

25%

ASTM E8

Hardness (Brinell), max

293 HBW (~32 HRC NACE)

ASTM E10 / E18

Charpy V-notch impact at −46 °C, min

45 J (NORSOK M-630)

ASTM E23 / ISO 148-1

Density

7.80 g/cm³

none

Modulus of elasticity

200 GPa (29 × 10³ ksi)

none

Duplex 2205 Physical Properties

Property	Value (Duplex 2205)
Density	7.80 g/cm³
Melting range	1385–1445 °C
Thermal conductivity at 20 °C	15 W/m·K
Coefficient of thermal expansion (20–100 °C)	13.0 × 10−6/°C
Specific heat at 20 °C	500 J/kg·K
Electrical resistivity at 20 °C	0.80 µΩ·m
Magnetic permeability	~50–100 (slightly magnetic, ferrite phase)

Property

Value (Duplex 2205)

Density

7.80 g/cm³

Melting range

1385–1445 °C

Thermal conductivity at 20 °C

15 W/m·K

Coefficient of thermal expansion (20–100 °C)

13.0 × 10−6/°C

Specific heat at 20 °C

500 J/kg·K

Electrical resistivity at 20 °C

0.80 µΩ·m

Magnetic permeability

~50–100 (slightly magnetic, ferrite phase)

Duplex 2205 Corrosion Properties

PREN = %Cr + 3.3·%Mo + 16·%N ≈ 35 typical per Duplex 2205 heat. Critical Pitting Temperature (CPT) per ASTM G48 method A: ~25 °C typical. Resistance to general corrosion in seawater, low-CO₂ oil & gas, organic-acid chemical processing. NACE MR0175 / ISO 15156 sour-service compliant when supplied solution-annealed with hardness ≤ 32 HRC and ferrite content 35–55% per NORSOK M-630.

Duplex 2205 Properties vs Super Duplex (Ferralium 255)

Property	Duplex 2205	Ferralium 255
Yield strength, min	450 MPa	550 MPa
Tensile strength, min	620 MPa	760 MPa
Elongation, min	25%	15%
PREN typical	~35	~40–42
CPT (ASTM G48 method A)	~25 °C	≥ 35 °C
Density	7.80 g/cm³	7.81 g/cm³
Reducing-acid resistance	Limited	Improved (2% Cu)

Property

Duplex 2205

Ferralium 255

Yield strength, min

450 MPa

550 MPa

Tensile strength, min

620 MPa

760 MPa

Elongation, min

25%

15%

PREN typical

~35

~40–42

CPT (ASTM G48 method A)

~25 °C

≥ 35 °C

Density

7.80 g/cm³

7.81 g/cm³

Reducing-acid resistance

Limited

Improved (2% Cu)

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 2205 Properties: Mechanical, Physical, Corrosion

Duplex 2205 Mechanical Properties

Duplex 2205 Physical Properties

Duplex 2205 Corrosion Properties

Duplex 2205 Properties vs Super Duplex (Ferralium 255)

Specifications

Surface Finish

Certifications

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