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Shanghai COCESS Special Alloys Co., Ltd. supplies High Quality Incoloy 925 (UNS N09925) Fasteners for sour oil & gas, subsea, and severe corrosion services. Our Incoloy 925 bolting—including hex head bolts, heavy hex bolts, double-end stud bolts, socket head cap screws, hex nuts, and washers—is machined from ASTM B805/B637 precipitation-hardenable bar stock, solution-annealed and aged to meet NACE MR0175 / ISO 15156 sour-service requirements (maximum HRC 35). Every shipment is accompanied by EN 10204 3.1 Mill Test Certificate, PMI verification, and full heat traceability.
Alloy 925 Fasteners — Sour-Service High-Strength Bolting
Incoloy 925 is a precipitation-hardenable nickel-iron-chromium alloy (Ni 42–46%, Cr 19.5–22.5%, Mo 2.5–3.5%, Cu 1.5–3.0%, Ti 1.9–2.4%, Al 0.10–0.50%). The Ti+Al addition enables γ′-Ni₃(Al,Ti) phase precipitation during aging, delivering yield strength ≥758 MPa (110 ksi) while retaining the excellent resistance to H₂S-induced sulfide stress corrosion cracking (SSC), pitting, and crevice corrosion found in Alloy 825.
This makes Incoloy 925 fasteners the preferred choice for:
Sour Oil & Gas (Upstream): wellhead stud bolts, Christmas tree flange bolts, subsurface safety valve fasteners, packer tie-down studs
Subsea & Offshore: manifold flange bolting, riser connector studs, seawater pump housing fasteners
Chemical Process: high-strength bolting for acid-handling vessels, heat exchanger channels exposed to H₂S/CO₂/chlorides
Fastener Types & Dimensional Standards
|
Fastener Type |
Size Range |
Dimensional Standard |
|---|---|---|
|
Hex Head Bolt (Hex Cap Screw) |
M6–M64 / 1/4"–2-1/2" |
ASME B18.2.1, ISO 4014/4017, DIN 931/933 |
|
Heavy Hex Bolt (for high-pressure flanges) |
M16–M64 / 5/8"–2-1/2" |
ASME B18.2.6, DIN 6914, EN 14399 |
|
Double-End Stud Bolt (Threaded Rod both ends) |
M10–M100 / 3/8"–4" |
ASME B16.5 flange companion, HG/T 20613 |
|
Socket Head Cap Screw (SHCS) |
M5–M36 / 1/4"–1-1/2" |
ASME B18.3, DIN 912 |
|
Hex Nut (Heavy / Regular) |
Matching bolt sizes |
ASME B18.2.2, DIN 934, ISO 4032 |
|
Plain Washer / Spring Washer |
Matching bolt sizes |
ASME B18.22.1, DIN 125/127 |
|
Specials: Eye bolt, U-bolt, anchor bolt, tap-end stud |
Per drawing |
— |
Thread forms: UNC, UNF, 8UN (flange studs), Metric coarse/fine
Surface finish: pickled & passivated (no electroplating—hydrogen embrittlement risk in sour service)
Head/stamp marking: UNS N09925 + Heat No. + NACE标识 per customer requirement
Chemical Composition — ASTM B805 / B637 (wt%)
|
Element |
Ni |
Cr |
Fe |
Mo |
Cu |
Ti |
Al |
C (max) |
Mn (max) |
Si (max) |
S (max) |
P (max) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Content (%) |
42.0–46.0 |
19.5–22.5 |
Bal. |
2.5–3.5 |
1.5–3.0 |
1.9–2.4 |
0.10–0.50 |
0.03 |
1.00 |
0.50 |
0.03 |
0.03 |
Mechanical Properties — Aged (Precipitation-Hardened) Condition
|
Condition |
Tensile Strength σb |
0.2% Yield Strength σ₀.₂ |
Elongation (4D) |
Hardness |
|---|---|---|---|---|
|
Solution Annealed |
≥ 685 MPa (99 ksi) |
≥ 270 MPa (39 ksi) |
≥ 30% |
≤ HRB 95 |
|
Solution Annealed + Aged* |
≥ 965 MPa (140 ksi) typ. 1030–1150 MPa |
≥ 758 MPa (110 ksi) typ. 790–860 MPa |
≥ 18–20% |
HRC 28–35 (NACE cap ≤ HRC 35) |
*Typical aging: 730–750°C soak + controlled cooling per ASTM B805 practice. Hardness is 100% batch-inspected to ensure compliance with NACE MR0175 / ISO 15156 Table A.10 for sour-service bolting.
Density: 8.08 g/cm³
Melting Range: 1311–1366°C (2400–2490°F)
Service Temp.: −196°C to 540°C continuous; short-term to ~650°C in low-corrosion environments
Quality Assurance & Certification
Mill Test Certificate: EN 10204 3.1 standard; 3.2 with TPI (SGS/BV/TÜV) available on request
PMI Testing: 100% positive material identification before dispatch
Hardness Verification: full-lot hardness mapping to confirm HRC ≤ 35 for sour-service application
Optional NDT: Magnetic Particle Inspection (MPI) per ASTM E709, Ultrasonic Test per ASTM A388 on critical studs
Traceability: heat number marked on bolt head / nut face, cross-referenced to MTC
Why Source Incoloy 925 Fasteners from Shanghai COCESS
Raw Material Control: Incoloy 925 bar stock sourced from qualified special melt mills, fully traceable to melt shop
NACE Compliance: dedicated hardness control & documentation for MR0175 sour-gas projects
Custom Machining: non-standard lengths, fine-pitch threads, reduced shank studs, counterbored nuts per drawing
Global Export: experienced in offshore-project packaging, dual-certification, and multi-language documentation
One-Stop Nickel Alloys: Incoloy 800H/825/926, Monel 400, Hastelloy C-276/C-22 fasteners available from same stock
Need a quote on Incoloy 925 stud bolts for API 6A flange, aged heavy hex bolts NACE MR0175, or full flange bolt/nut/washer sets?
Contact Shanghai COCESS Special Alloys Co., Ltd. for stock availability, MTC sample, and competitive export pricing.
???? Email: sales@cocessalloys.com
