Surface Treatments
Certifications
- 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
Ferralium 255 Hex Bolts (UNS S32550), ASME B18.2.1
Ferralium 255 hex bolts are machined from ASTM A479 (UNS S32550) bar with ASME B18.2.1 dimensional standard (UNC inch and metric M). Manufactured at TorqBolt's Mumbai & Rajkot, India facilities. Per-heat Mill Test Certificate (EN 10204 type 3.2) certifies hardness ≤ 32 HRC for NACE MR0175 sour-service compliance. NORSOK M-650 QTR available on request for North Sea / Norwegian offshore service.
Dimensional Standards
| Bolt type | Inch series | Metric series |
|---|---|---|
| Hex bolts | ASME B18.2.1 (UNC / UNF) | ASME B18.2.3.1M / DIN 933 (M) |
| Heavy hex bolts | ASME B18.2.1 | ASME B18.2.3.6M |
| Hex cap screws | ASME B18.2.1 | DIN 933 (full thread) / DIN 931 (partial thread) |
Material & Properties
Bar stock per ASTM A479 (UNS S32550): Cr 24–27%, Ni 4.5–6.5%, Mo 2.9–3.9%, Cu 1.5–2.5%, N 0.10–0.25%. Solution-annealed at 1100 °C + water quench. Bolt mechanical properties: yield ≥ 550 MPa, tensile ≥ 760 MPa, elongation ≥ 15%, hardness 25–32 HRC (controlled to NACE MR0175 limit). PREN ≥ 40, CPT ≥ 35 °C per ASTM G48 method A.
Size Range
| Series | Diameter range | Length range |
|---|---|---|
| UNC inch | 1/4" through 4" | up to 36" |
| Metric (M) | M6 through M100 | up to 1000 mm |
Typical Applications
- Seawater service, pump casings, manifold flanges, valve bonnet bolting, firewater system flanges
- Oil & gas downhole, wellhead bolting, X-mas tree internals (NACE MR0175 sour service)
- Subsea offshore, flowline / riser flange bolting, connector studs (NORSOK M-650 qualified)
- Chemical processing, reactor flange bolting in HCl, H2SO4, brine service
- Desalination, reverse-osmosis high-pressure pump flange bolting
Matched Fasteners (full B16.5 flange set)
Hex bolts are typically supplied with paired fasteners for ASME B16.5 flange connections: Ferralium 255 hex nuts (ASTM A479 material per ASME B18.2.2), flat washers (ASTM A479 material per ASME B18.22.1), and where stud bolts are preferred, Ferralium 255 stud bolts (ASTM A193 S6 / ASME B18.31.2). All paired fasteners come from the same heat where possible to ensure matched corrosion behaviour in service.
Documentation
- Per-heat EN 10204 type 3.2 Mill Test Certificate, chemistry, mechanical properties, ferrite content, PREN, hardness
- NORSOK M-650 QTR available on request for offshore projects
- NACE MR0175 / ISO 15156-3 sour-service compliance per heat
- Dimensional inspection report per ASME B18 series
- NDT report (UT / DPT / MPI) when specified
Need Ferralium 255 hex bolts? Email info@torqbolt.com or WhatsApp +91-22-66157017 with form, dimensions, quantity, ASTM/EN spec, MTC level (3.1 / 3.2). NACE MR0175 sour-service stamp on every heat. NORSOK M-650 QTR on request. Per-heat EN 10204 type 3.2 MTC included with every consignment.
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