Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175 / ISO 15156-2
- NORSOK M-650 Qualified
- API 6A Certified
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Super Duplex 2507 Stud Bolts
From TorqBolt (Mumbai, India): Super Duplex 2507 stud bolts (UNS S32750 / EN 1.4410) are the standard fastener for high-pressure flange connections in seawater, sour-service, and oil-and-gas piping. The bolting material itself is ASTM A1082 / API 20F; dimensional patterns follow ASME B18.31.2 (continuously threaded studs). Companion components are heavy hex nuts and flat washers in matching S32750 chemistry per A1082.
The dedicated standard for super duplex bolting is ASTM A1082/A1082M (high-strength precipitation hardening and duplex stainless steel bolting material), supplemented by API 20F for corrosion-resistant bolting in petroleum and natural gas service. TorqBolt manufactures under WPS qualified to NORSOK M-650 at the Mumbai facility, with hardness restricted to 28 HRC max for NACE MR0175 / ISO 15156-3 sour-service compliance.
Super Duplex 2507 Stud Bolts Size Range
Stud bolts are supplied to ASME B16.5 raised-face flange standard lengths. Diameter range is 1/2 inch through 3 inches under ASME B16.5, and up to 6 inches for B16.47 Series A/B large-bore flanges. Length is fixed by flange class (150, 300, 600, 900, 1500, or 2500) and bore size, not by user preference. Threading is full thread (no shank) per ASME B16.5 and TC-04-0001 (ExxonMobil practice). Pitch is 8UN above 1 inch diameter and UNC below 1 inch. Every stud is furnished with two ASTM A194 Grade 2H heavy hex nuts as a matched set, heat-numbered together.
| Flange Class | Bore | Stud Size | Length | Quantity |
|---|---|---|---|---|
| 300 | 4 inch | 7/8-9 UNC | 6.25 inch | 16 |
| 600 | 6 inch | 7/8-9 UNC | 8.5 inch | 16 |
| 900 | 8 inch | 1-1/8-8 UN | 11.75 inch | 20 |
| 1500 | 4 inch | 1-1/4-8 UN | 10.25 inch | 12 |
Super Duplex 2507 Stud Bolts Standards
| Standard | Scope |
|---|---|
| ASTM A1082 / A1082M | Dedicated standard, High-Strength Precipitation Hardening and Duplex Stainless Steel Bolting Material. Covers UNS S32750 (Type 2507) explicitly. |
| API 20F | Corrosion-Resistant Bolting for Petroleum and Natural Gas Industries (BSL-2, BSL-3) |
| ASTM A962/A962M | General requirements for stainless steel bolting (A1082 §1.2 companion) |
| ASTM A479 | Bar stock chemistry and properties (raw stock for machining) |
| ASTM A276 | Bar and shapes (alternate raw stock) |
| ASME B18.31.2 | Dimensional specification |
| ASME B1.1 / ISO 261 | Inch / metric thread call-outs |
| NORSOK L-005 | Compact flange connections (NCS reference) |
| NORSOK M-630 | Material data sheet (MDS D55, D57) |
| NORSOK M-650 | Manufacturer qualification (QTR) |
| NACE MR0175 / ISO 15156-3 | Sour-service compliance, 28 HRC max |
| API 6A PSL 3 / 3G | Wellhead and christmas tree fasteners |
| API 17D | Subsea wellhead and tree fasteners |
Super Duplex 2507 Mechanical Properties (per ASTM A1082)
| Property | Minimum | Typical |
|---|---|---|
| Tensile strength | 800 MPa (116 ksi) for ≤ 2 in. / 760 MPa (110 ksi) for > 2 in. | 800 to 1000 MPa |
| Yield strength (0.2 percent offset) | 550 MPa (80 ksi) for ≤ 2 in. / 515 MPa (75 ksi) for > 2 in. | 620 to 720 MPa |
| Elongation in 4D | 15 percent | 25 to 35 percent |
| Reduction of area | 33 percent | 40 percent |
| Hardness (A1082) | 310 HBN max | 250 to 300 HBN |
| Hardness (NACE sour-service) | 28 HRC max | 25 to 28 HRC |
| Charpy V-notch at minus 46 degrees Celsius | 45 J min | 60 to 100 J |
| PREN | 40 min | 41 to 43 |
Heat Treatment
Solution annealing at 1025 to 1125 degrees Celsius per A1082 (NORSOK M-630 narrows to 1040 to 1100 degrees Celsius), followed by rapid water quench. There is no aging or precipitation hardening; strength comes from the duplex austenite-ferrite microstructure itself. Final hardness check confirms 28 HRC maximum for NACE MR0175 compliance.
Super Duplex 2507 Chemistry per ASTM A1082
| Element | A1082 Min % | A1082 Max % |
|---|---|---|
| Carbon | (no min) | 0.030 |
| Manganese | (no min) | 1.20 |
| Phosphorus | (no min) | 0.035 |
| Sulfur | (no min) | 0.020 |
| Silicon | (no min) | 0.80 |
| Chromium | 24.0 | 26.0 |
| Nickel | 6.0 | 8.0 |
| Molybdenum | 3.0 | 5.0 |
| Nitrogen | 0.24 | 0.32 |
| Copper | 0.50 max, residual, not intentional | |
Companion Products
All companion components in matching UNS S32750 chemistry per A1082.
- Bolts, A1082 in S32750
- Stud bolts, A1082 in S32750, ASME B18.31.2
- Heavy hex nuts, A1082 in S32750, 8MA pattern
- Flat washers, UNS S32750, F436 dimensional pattern by special order
- Mating flanges, ASTM A182 F53
Super Duplex 2507 Stud Bolts Applications
Stud bolts are the workhorse of ASME B16.5 and B16.47 flange bolting in oil and gas, refining, chemical processing, and seawater service. Super Duplex 2507 takes over wherever ASTM A193 B7 fails on chloride pitting, sour-service hardness limits, or pitting equivalent (PREN) requirements above 40. The top duty cycles run hot, run sour, or run wet, and the matched-set studs and nuts ship under EN 10204 Type 3.1 or 3.2 with PMI tags per ASTM E1476.
- Subsea wellhead and christmas tree connectors, API 17D Material Class HH service
- Topside production manifolds, chloride-laden splash-zone environment per API 20F BSL-3
- FPSO seawater lift caissons, sea-chest and fire-water deluge flange bolting
- Desalination high-pressure RO membrane vessels, brine reject loop flanges at 70 bar
- FGD absorber tower flange joints, wet limestone slurry with chloride concentration up to 30,000 ppm
- Geothermal wellhead bolting, CO2 plus H2S service per NACE MR0175 28 HRC limit
- Heat exchanger tubesheet bolting, reactor and column flanges in pulp bleach plant service
Super Duplex 2507 Stud Bolts FAQ
Why are stud bolts threaded full length rather than partially threaded like hex bolts?
Full thread allows compression of two adjacent raised-face flanges with washers stacked on either side if the joint geometry calls for it. It also lets a single stud diameter cover a range of grip lengths without re-cutting threads. In corroded service, full thread eases breakout: a seized nut can be backed off across the entire shaft length, so the stud rarely shears at the thread runout the way a partially threaded bolt does. ASME B16.5 and TC-04-0001 both mandate full thread for raised-face flange bolting.
How are Super Duplex 2507 stud bolts tensioned in subsea service?
Hydraulic tensioning per API 6A and API 17D, not torque wrench. Stretch the stud to 50 percent of specified minimum yield (275 MPa residual on a 550 MPa yield grade), measured by tensioner gauge pressure and verified by ultrasonic bolt-length measurement. Lubricant practice follows ASTM A193 B7 convention, but always consult NACE MR0175 for galvanic compatibility with the flange material and the subsea coating system.
What lubricant is approved for Super Duplex 2507 stud bolts on duplex flanges?
Nickel-based anti-seize is the industry default for Super Duplex 2507 on F53 flanges. Molybdenum disulfide is also accepted for dry topside service. PTFE-based lubricants are preferred in sour service where sulfide stress cracking risk is high. Avoid copper-based anti-seize on duplex flanges: copper plating sets up a galvanic cell with the duplex ferrite phase under wet chloride exposure and accelerates pitting.
What length stud bolt do I need for a 6 inch class 600 raised-face flange?
Per ASME B16.5 Table II-2, a 6 inch class 600 raised-face flange takes 7/8-9 UNC stud bolts, 8.5 inch length, quantity 16, supplied with 32 matching ASTM A194 Grade 2H heavy hex nuts. Add a spiral wound gasket per ASME B16.20 and the joint is complete. For a 6 inch class 900 RF flange the size jumps to 1-1/8-8 UN, 9.75 inch length, quantity 12.
Can stud bolts and nuts be supplied as matched sets with PMI tags?
Yes. Every order ships studs and nuts heat-numbered together as a matched assembly, with positive material identification per ASTM E1476 using portable X-ray fluorescence on the stud shank and each nut face. Heat traceability is documented per Section 8 of NORSOK M-650 QTR: heat number, melt practice, solution-anneal record, mechanical test results, and PMI scan all referenced on the EN 10204 Type 3.1 certificate. Type 3.2 third-party-witnessed is available on request.
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