High-Performance Duplex & Super Duplex Bolting Technology
Duplex stainless steels possess a balanced two-phase microstructure consisting of approximately 50% austenite and 50% ferrite. This metallurgical design yields roughly twice the mechanical yield strength of standard austenitic grades (such as AISI 304 or 316L), paired with exceptional resistance to pitting, crevice corrosion, and chloride-induced stress corrosion cracking (CSCC).
TorqBolt Inc. is an established manufacturer supplying fully certified Duplex and Super Duplex fasteners for mission-critical assemblies in seawater systems, high-pressure desalination facilities, sour gas wells, and petrochemical process equipment. All products are formed using controlled hot forging or precision CNC machining to maintain grain flow integrity and eliminate hazardous intermetallic phase formations (sigma & chi phases).
Duplex 2205 (UNS S32205 / S31803)
The workhorse industrial grade with a Pitting Resistance Equivalent Number (PREN) ≥ 34–35. Ideal for environments exceeding the corrosion threshold of standard 316L stainless steel.
- Yield Strength: ≥ 450–550 MPa (65–80 ksi)
- Tensile Strength: ≥ 680–880 MPa (98–128 ksi)
- Operating Temp: -50°C to +300°C
- Standard Specs: ASTM A276, ASTM A479, ASME SA-182 F51 / F60
Super Duplex 2507 (UNS S32750)
Highly alloyed with 25% Chromium, 4% Molybdenum, and 0.28% Nitrogen (PREN ≥ 42). Engineered specifically for aggressive chloride-rich topside and subsea marine applications.
- Yield Strength: ≥ 550 MPa (80 ksi)
- Tensile Strength: ≥ 750–1000 MPa (110–145 ksi)
- Charpy Impact: ≥ 80 J at -46°C
- Standard Specs: ASTM A276, ASTM A479, ASME SA-182 F53
Zeron 100 (UNS S32760 / F55)
Enhanced Super Duplex formulated with controlled Tungsten (0.5–1.0%) and Copper additions to provide superior crevice resistance in hot sulfuric and hydrochloric acid streams.
- Yield Strength: ≥ 550 MPa (80 ksi)
- Tensile Strength: ≥ 750–1000 MPa (110–145 ksi)
- PREN: ≥ 42 (Cr + 3.3[Mo + 0.5W] + 16N)
- Standard Specs: ASTM A276, ASTM A479, ASME SA-182 F55
Manufactured Product Form Factors & Size Range
Every fastener is produced in accordance with strict international dimensional and metallurgical guidelines, ready for worldwide deployment.
Hex Head & Heavy Hex Bolts
Engineered for high-pressure flange assemblies. Available in full-thread tap bolts and partial-thread configurations per ASME B18.2.1, DIN 931, DIN 933, and ISO 4014/4017.
Continuous & Engineered Studs
All-thread stud bolts, double-end studs, and collar studs suited for ASME B16.5 and B16.47 piping flanges. Fully compliant with ASTM A193 / A320 dimensional tolerances.
Heavy Hex & Flange Nuts
Hardness-matched mating nuts preventing galling under sustained clamp loads. Manufactured per ASME B18.2.2, ASTM A194 Gr. 8M / Gr. 9C, DIN 934, and ISO 4032.
Washers & Engineered Parts
Through-hardened flat washers, Belleville disc springs, lock washers, and CNC-machined components machined directly from certified bar stock to client drawings.
| Alloy Grade | UNS Number | Cr (%) | Ni (%) | Mo (%) | N (%) | Min. Yield (MPa) | Min. Tensile (MPa) | Hardness (Max) |
|---|---|---|---|---|---|---|---|---|
| Duplex 2205 | S32205 / S31803 | 22.0 – 23.0 | 4.5 – 6.5 | 3.0 – 3.5 | 0.14 – 0.20 | 450 | 655 – 880 | 28 HRC / 290 HBW |
| Super Duplex 2507 | S32750 | 24.0 – 26.0 | 6.0 – 8.0 | 3.0 – 5.0 | 0.24 – 0.32 | 550 | 750 – 1000 | 32 HRC / 310 HBW |
| Super Duplex Zeron 100 | S32760 | 24.0 – 26.0 | 6.0 – 8.0 | 3.0 – 4.0 | 0.20 – 0.30 | 550 | 750 – 1000 | 32 HRC / 310 HBW |
Composition ranges and mechanical limits per ASTM A276/A479. Custom tensile, yield, and cryogenic impact requirements can be accommodated upon request.
Quality Control, Testing & Third-Party Inspection
Given the susceptibility of dual-phase stainless steels to deleterious intermetallic phase precipitation during thermal cycles, TorqBolt enforces exhaustive verification testing on every production lot.
Ferrite Phase Balance
Quantitative point counting per ASTM E562 and Feritscope checking confirming a 40% to 60% phase distribution, preventing localized cracking.
Corrosion Rate Testing
Ferric chloride pitting tests conducted per ASTM A923 Method C (at 25°C for 2205; 40°C for 2507/Zeron 100) ensuring corrosion rate is below 10 mdd.
Sub-Zero Impact Toughness
Charpy V-notch impact testing performed at -46°C (-50°F) per ASTM A370 to ensure ductile-to-brittle transition temperatures comply with NORSOK standards.
Non-Destructive Examination
Liquid penetrant inspection (PT), 100% Positive Material Identification (PMI via XRF spectrometers), and precise optical thread gauging.