Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASTM A1082/A1082M Grade S32550 | Ferralium 255 Super Duplex Steel
High-strength super duplex alloy providing superior resistance in aggressive media
Grade S32550 (UNS S32550) is a high-alloyed super duplex stainless steel, widely recognized as Ferralium 255, containing 25% chromium, 5% nickel, 3% molybdenum, and 2% copper to provide exceptional resistance to corrosion in aggressive acidic and chloride-rich environments. Designated as ASTM A1082/A1082M F61, this grade features a dual-phase microstructure that delivers nearly double the yield strength of standard austenitic stainless steels, combined with superior resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC). S32550 is specifically engineered for demanding applications in the chemical processing, offshore oil and gas, marine, and pulp and paper industries where mechanical durability and long-term structural integrity are required. Its unique copper addition enhances resistance to non-oxidizing acids like sulfuric and phosphoric acid, making it ideal for pumps, valves, fasteners, and complex marine hardware.
ASTM A1082/A1082M Grade S32550 Chemical RequirementsA
| Grades | UNS Designation | Type | C | Mn | P | S | Si | Cr | Ni | Mo | N | Other ElementsB |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ASTM A1082/A1082M Duplex (Ferritic-Austenitic) Grades | S32550 | 255 | 0.040 | 1.50 | 0.040 | 0.030 | 1.00 | 24.0-27.0 | 4.5-6.5 | 2.9-3.9 | 0.10-0.25 | Cu 1.50-2.50 |
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ASTM A1082/A1082M Grade S32550 Mechanical Properties
| UNS Designation | Solution Temperature, °F [°C] (B, C) | Tensile Strength, min, ksi [MPa] | Yield Strength, 0.2% offset, min, ksi [MPa] | Elongation in 2" [50 mm] or 4D, min, % | Rockwell HRC, max | Brinell max (D) |
|---|---|---|---|---|---|---|
| S32550 | 1900 [1040] | 110 [760] | 80 [550] | 15 | 31 | 297 |
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ASTM A1082/A1082M Markings
| UNS Designation | Type | Grade Symbol |
|---|---|---|
| S32550 | 255 | TB 32550 |
Frequently Asked Questions
What is Ferralium 255 (S32550)?
Ferralium 255 (S32550) is a stainless steel grade covered under ASTM A1082/A1082M for high-strength bolting in special-purpose applications such as pressure vessels. UNS designation S32550. Available as bolts, studs, screws and nuts manufactured by TorqBolt for global oil/gas/nuclear/power/marine sectors.
What are the mechanical properties of Ferralium 255 (S32550) per ASTM A1082?
Mechanical property requirements for S32550 are defined in ASTM A1082 Table 2 (PH grade solution treatment) or Table 4 (duplex annealed condition). Properties vary by treatment condition - refer to the bolting specification for the H-condition (PH) or annealed yield/tensile/elongation/hardness requirements applicable to your order.
Is Ferralium 255 (S32550) suitable for sour service (NACE MR0175)?
Refer to NACE MR0175 / ISO 15156 Tables A.16-A.19. Most A1082 duplex grades are permitted at ≤28 HRC; PH grades require condition-specific qualification (typically H1150 for 17-4 PH at 28 HRC). TorqBolt supplies sour-service certified product on request with full PMI + hardness traceability.
What ASME / ISO dimensional standards can Ferralium 255 (S32550) be supplied to?
This grade is available across the full ASME and ISO bolting dimensional standards covered on this site - ASME B18.2.1 (hex bolts, hex cap screws, lag screws), B18.2.2 (hex nuts, square nuts, lock nuts), B18.3 (socket head cap screws), B18.31.2 (clamping studs), B16.5 (flange stud bolts), ISO 4032 / 4033 / 4035 (metric nuts), and metric B18.2.3.xM / B18.2.4.xM series.
References & Standards
- ASTM A1082 / A1082M - Standard Specification for High-Strength Precipitation-Hardening and Duplex Stainless Steel Bolting for Special-Purpose Applications (current edition 2016, active)
- ASTM A962 / A962M - General Requirements for Special-Purpose Bolting Materials
- ASTM A370 - Mechanical Testing of Steel Products
- NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum & natural gas industries
- ASME B18 series - Dimensional standards for bolts, screws, nuts, studs
- ISO 4032 / 4033 / 4035 - Metric hexagon nut dimensional standards
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