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 Eye Bolts
From TorqBolt (Mumbai, India): Super Duplex 2507 eye bolts in UNS S32750 are forged-head lifting fasteners for marine, offshore, and chemical-plant lifting points where chloride and sour-service exposure rules out carbon steel. Material conforms to ASTM A1082 (forged eye section) with safe working load (SWL) tested per ASME B30.26 or EN 13155.
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 Eye Bolts Size Range
Eye bolts are forged to ASTM F541 (lifting eye bolts) and DIN 580 (forged ring bolt). Thread shank diameters cover 1/4 inch through 3 inches UNC (US series) and M6 through M48 metric per DIN 580. Two head styles are produced: shouldered (rated for angle loading down to 45 degrees) and shoulderless (straight pull only). The eye is hot upset on the bar end, then the complete bolt is solution annealed at 1040 to 1100 degrees Celsius and water quenched in one batch alongside the parent material. Shoulder thickness and eye internal diameter follow the dimensional standard. The Working Load Limit (WLL) is published for three pull directions: straight pull (full rating), 45 degrees (50 percent of WLL), and 90 degrees (25 percent of WLL).
| Size | Standard | Style | WLL straight pull | WLL at 45 degrees | WLL at 90 degrees |
|---|---|---|---|---|---|
| M16 | DIN 580 shouldered | Shouldered | 700 kg | 350 kg | 175 kg |
| 1/4 in. to 3 in. UNC | ASTM F541 | Shouldered or shoulderless | per F541 Table 2 | 50 percent of WLL | 25 percent of WLL |
| M6 to M48 | DIN 580 | Shouldered or shoulderless | per DIN 580 Table 1 | 50 percent of WLL | 25 percent of WLL |
Super Duplex 2507 Eye 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 B18.15, DIN 580 / 582 | 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 Eye Bolts Applications
Eye bolts in Super Duplex 2507 are specified wherever chloride attack would defeat a carbon steel or 304L lifting eye. Typical service locations include offshore module lifting and rigging on FPSO topsides, subsea jumper installation hardware, lifting points on seawater pump skids, deck cargo tie-down hardware for chemical tanker fittings, desalination plant skid relocation eyes, and lifting points on splash-zone vessels where salt-water wash-down is constant.
- Offshore and subsea, FPSO topside module lifting, subsea jumper installation, BOP rigging eyes per API 17D
- Seawater service, seawater pump skid lifting points, sea-chest cover handling eyes, fire-water pump rigging
- Chemical tanker deck hardware, cargo tie-down eyes, hose-handling crane eyes per API 20F
- Desalination, RO skid relocation eyes, brine pump lifting points
- FGD and splash-zone vessels, wet absorber tower internal lifting lugs, splash-zone platform rigging
- Chemical processing, reactor cover handling eyes, heat exchanger bundle lifting
Super Duplex 2507 Eye Bolts FAQ
What is the working load limit (WLL) of a Super Duplex 2507 eye bolt versus carbon steel?
The WLL of a 2507 eye bolt is lower in absolute MPa than a quenched and tempered carbon steel eye bolt because 2507 is an austenite plus ferrite duplex with a yield of 550 MPa, while a quenched and tempered alloy steel eye bolt yields around 800 MPa. The designed safety factor is 5 to 1 per ASME B30.26 in both cases, so the WLL ratio tracks the yield ratio. The trade is corrosion resistance: a 2507 eye bolt remains in service in chloride splash zones where a carbon steel eye bolt would be condemned within months.
When do I need a shouldered eye bolt versus shoulderless?
A shouldered eye bolt is required for any lift where the rigging may pull at an angle to the shank axis. The shoulder seats against the load surface and reacts the side load, allowing rated capacity down to 45 degrees off vertical. A shoulderless (eye nut style) eye bolt is permitted only for straight vertical pull. Using a shoulderless eye bolt at any angle is a rigging violation under ASME B30.26.
Are Super Duplex 2507 eye bolts proof-load tested?
Yes. A representative sample from each heat is proof-load tested at twice the WLL per ASTM F541 Section 11. The proof test is non-destructive at this load and verifies both the forged eye and the threaded shank. Every shipment is supplied with the proof-test certificate referenced to the heat number on the mill test certificate.
What is the chloride pitting margin advantage over 316L eye bolts?
Super Duplex 2507 has a PREN of 42 versus 26 for 316L, which corresponds to roughly twice the chloride threshold concentration before pitting initiates. Measured Critical Pitting Temperature (CPT) per ASTM G48 Method E is approximately 50 degrees Celsius for 2507 versus 15 degrees Celsius for 316L. In seawater splash service the practical outcome is that 316L eye bolts pit within months while 2507 eye bolts survive the design life of the host structure.
Can the eye thread be supplied as metric M-series with a UNC shank for retrofit?
Yes on quotation. Combination threading (metric M-series in the eye end with UNC in the shank, or the inverse) is supplied as a special order for retrofit into existing equipment where the host thread is not negotiable. Combination threading requires an NDE re-check on the transition shoulder because the forging flow lines change at the thread change-over, and a revised proof-test certificate is issued against the as-built combination geometry.
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