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.

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Ferralium 255 Chemical Composition (UNS S32550)

Ferralium 255 chemical composition per ASTM A479 / EN 10088-3:

Element	Min %	Max %
Carbon (C)	none	0.04
Chromium (Cr)	24.0	27.0
Nickel (Ni)	4.5	6.5
Molybdenum (Mo)	2.9	3.9
Copper (Cu)	1.5	2.5
Nitrogen (N)	0.10	0.25
Manganese (Mn)	none	1.5
Silicon (Si)	none	1.0
Phosphorus (P)	none	0.04
Sulphur (S)	none	0.03

ASTM A479
ASTM A789
ASTM A790
ASTM A815
ASTM A182
ASTM A276
EN 10088-3
EN 10222-5

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

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