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Inconel 625 fasteners are precision-engineered nickel-chromium-molybdenum alloy fastening components designed for service in high-temperature, high-pressure, and severely corrosive environments. Conforming to ASTM B446 / UNS N06625, these fasteners deliver exceptional resistance to oxidation, pitting, crevice corrosion, and stress-corrosion cracking — making them the specified choice for offshore oil & gas platforms, marine engineering, chemical processing plants, and aerospace structural assemblies.
| Material | Inconel 625 (UNS N06625), Nickel-Chromium-Molybdenum Alloy |
| Grade Options | Annealed, Solution Annealed, Cold Worked |
| Size Range | M3 to M100 | 1/4" to 4" diameter |
| Thread Type | Metric (ISO), UNC, UNF, BSW |
| Standards | ASTM B446, ASTM B564, ASME SB446, DIN, ISO |
| Surface Finish | Bright, Pickled, Passivated, Polished |
| Types | Bolts, Nuts, Washers, Studs, Socket Head Cap Screws |
| Tensile Strength | Up to 827 MPa (Annealed condition) |
| Hardness | Up to 90 HRB (typical range) |
| Grade | C | Mn | Si | S | Cu | Fe | Ni | Cr |
| Inconel 625 | 0.10 max | 0.50 max | 0.50 max | 0.015 max | - | 5.0 max | 58.0 min | 20.0 - 23.0 |
| Element | Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
| Inconel 625 | 8.4 g/cm3 | 1350 °C (2460 °F) | Psi – 1,35,000 , MPa – 930 | Psi – 75,000 , MPa – 705 | 42.5 % |
| STANDARD | WERKSTOFF NR. | UNS | JIS | BS | GOST | AFNOR | EN |
| Inconel 625 | 2.4856 | N06625 | NCF 625 | NA 21 | ХН75МБТЮ | NC22DNB4M | NiCr22Mo9Nb |
| Class 150 Flanges ASME B16.5 (Stud bolt sizes) | Length of Stud Bolts | |||||||
| NPS | Outside Diameter of Flange | The diameter of Bolt Circle | The diameter of Bolt Holes | Number of Bolts | Diameter of Bolts | Raised Face 0.06 in |
Ring Joint | |
| 1/2 | 3 1/2 | 2 3/8 | 5/8 | 4 | 1/2 | 2 1/4 | – | |
| 3/4 | 3 7/8 | 2 3/4 | 5/8 | 4 | 1/2 | 2 1/2 | – | |
| 1 | 4 1/4 | 3 1/8 | 5/8 | 4 | 1/2 | 2 1/2 | 3 | |
| 1 1/4 | 4 5/8 | 3 1/2 | 5/8 | 4 | 1/2 | 2 3/4 | 3 1/4 | |
| 1 1/2 | 5 | 3 7/8 | 5/8 | 4 | 1/2 | 2 3/4 | 3 1/4 | |
| 2 | 6 | 4 3/4 | 3/4 | 4 | 5/8 | 3 1/4 | 3 3/4 | |
| 2 1/2 | 7 | 5 1/2 | 3/4 | 4 | 5/8 | 3 1/2 | 4 | |
| 3 | 7 1/2 | 6 | 3/4 | 4 | 5/8 | 3 1/2 | 4 | |
| 3 1/2 | 8 1/2 | 7 | 3/4 | 8 | 5/8 | 3 1/2 | 4 | |
| 4 | 9 | 7 1/2 | 3/4 | 8 | 5/8 | 3 1/2 | 4 | |
| 5 | 10 | 8 1/2 | 7/8 | 8 | 3/4 | 3 3/4 | 4 1/4 | |
| 6 | 11 | 9 1/2 | 7/8 | 8 | 3/4 | 4 | 4 1/2 | |
| 8 | 13 1/2 | 11 3/4 | 7/8 | 8 | 3/4 | 4 1/4 | 4 3/4 | |
| 10 | 16 | 14 3/4 | 1 | 12 | 7/8 | 4 1/2 | 5 | |
| 12 | 19 | 17 | 1 | 12 | 7/8 | 4 3/4 | 5 1/4 | |
| 14 | 21 | 18 3/4 | 1 1/8 | 12 | 1 | 5 1/4 | 5 3/4 | |
| 16 | 23 1/2 | 21 1/4 | 1 1/8 | 16 | 1 | 5 1/4 | 5 3/4 | |
| 18 | 25 | 22 3/4 | 1 1/4 | 16 | 1 1/8 | 5 3/4 | 6 1/4 | |
| 20 | 27 1/2 | 25 | 1 1/4 | 20 | 1 1/8 | 6 1/4 | 6 3/4 | |
| 24 | 32 | 29 1/2 | 1 1/4 | 20 | 1 1/4 | 6 3/4 | 7 1/4 | |
| Class 300 Flanges ASME B16.5 | Length of Stud Bolts | |||||||
| NPS | Outside Diameter of Flange | The diameter of Bolt Circle | The diameter of Bolt Holes | Number of Bolts | Diameter of Bolts | Raised Face 0.06 in |
Ring Joint | |
| 1/2 | 3 3/4 | 2 5/8 | 5/8 | 4 | 1/2 | 2 1/2 | 3 | |
| 3/4 | 4 5/8 | 3 1/4 | 3/4 | 4 | 5/8 | 3 | 3 1/2 | |
| 1 | 4 7/8 | 3 1/2 | 3/4 | 4 | 5/8 | 3 | 3 1/2 | |
| 1 1/4 | 5 1/4 | 3 7/8 | 3/4 | 4 | 5/8 | 3 1/4 | 3 3/4 | |
| 1 1/2 | 6 1/8 | 4 1/2 | 7/8 | 4 | 3/4 | 3 1/2 | 4 | |
| 2 | 6 1/2 | 5 | 3/4 | 8 | 5/8 | 3 1/2 | 4 | |
| 2 1/2 | 7 1/2 | 5 7/8 | 7/8 | 8 | 3/4 | 4 | 4 1/2 | |
| 3 | 8 1/4 | 6 5/8 | 7/8 | 8 | 3/4 | 4 1/4 | 4 3/4 | |
| 3 1/2 | 9 | 7 1/4 | 7/8 | 8 | 3/4 | 4 1/4 | 5 | |
| 4 | 10 | 7 7/8 | 7/8 | 8 | 3/4 | 4 1/2 | 5 | |
| 5 | 11 | 9 1/4 | 7/8 | 8 | 3/4 | 4 3/4 | 5 1/4 | |
| 6 | 12 1/2 | 10 5/8 | 7/8 | 12 | 3/4 | 4 3/4 | 5 1/2 | |
| 8 | 15 | 13 | 1 | 12 | 7/8 | 5 1/2 | 6 | |
| 10 | 17 1/2 | 15 1/4 | 1 1/8 | 16 | 1 | 6 1/4 | 6 3/4 | |
| 12 | 20 1/2 | 17 3/4 | 1 1/4 | 16 | 1 1/8 | 6 3/4 | 7 1/4 | |
| 14 | 23 | 20 1/4 | 1 1/4 | 20 | 1 1/8 | 7 | 7 1/2 | |
| 16 | 25 1/2 | 22 1/2 | 1 3/8 | 20 | 1 1/4 | 7 1/2 | 8 | |
| 18 | 28 | 24 3/4 | 1 3/8 | 24 | 1 1/4 | 7 3/4 | 8 1/4 | |
| 20 | 30 1/2 | 27 | 1 3/8 | 24 | 1 1/4 | 8 | 8 3/4 | |
| 24 | 36 | 32 | 1 5/8 | 24 | 1 1/2 | 9 | 10 | |
Inconel 625 fasteners are used wherever standard austenitic stainless steel fasteners fail due to corrosion, elevated temperature, or combined stress and chemical attack. Their primary service environments span offshore structures, chemical process plants, aerospace systems, and cryogenic equipment.
Inconel 625 fasteners at KK Fasteners are produced through a combination of hot forging (for larger diameters above M30) and CNC cold heading or turning (for smaller precision fasteners). Thread rolling — rather than cutting — is applied wherever tolerances and surface finish requirements demand it, as rolled threads in Alloy 625 exhibit a 15–20% improvement in fatigue life versus cut threads.
Every production lot undergoes dimensional inspection per ISO 4759-1, hardness testing per ASTM E18, PMI (Positive Material Identification) verification via XRF, and hydrostatic or proof load testing on request. Material is sourced from qualified mills with full EN 10204 Type 3.1 or 3.2 certification traceability. KK Fasteners operates under an ISO 9001:2015 certified quality management system, and third-party inspection by SGS, BV, or TÜV can be accommodated at the client’s direction.
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Inconel 625 fasteners are bolts, nuts, studs, and threaded rods manufactured from UNS N06625 nickel-chromium-molybdenum alloy. They are specified for high-temperature, high-pressure, and severely corrosive applications — including offshore, chemical processing, and aerospace service — where standard stainless steel fasteners lack sufficient corrosion or heat resistance.
Inconel 600 (UNS N06600) contains no molybdenum and offers moderate corrosion resistance, primarily for high-temperature oxidizing atmospheres. Inconel 625 adds 8–10% Mo and niobium, giving it dramatically superior resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride-containing environments. For subsea, sour gas, or mixed acid service, Alloy 625 is the correct choice; Alloy 600 is adequate for dry high-heat applications without aggressive chemical exposure.
The primary material standard is ASTM B446 (bar and wire for fasteners), with ASME SB446 as the pressure vessel code equivalent. For finished fasteners used in ASME-code construction, the relevant dimensional standards are ASME B18.2.1 (hex bolts, inch series), ASME B18.2.2 (hex nuts), and ASME B16.5 (stud bolts for flanges). For sour service qualification, ISO 15156-3 / NACE MR0175 applies.
Selection depends on three factors: service temperature, chemical environment, and mechanical load. For temperatures above 650°C in oxidizing conditions, standard annealed Grade 1 (ASTM B446 Gr. 1) is appropriate. For cryogenic or sub-ambient service down to –196°C, the same grade is rated suitable. For joints requiring higher preload than the annealed condition provides, inquire about cold-worked or strain-hardened material to ASTM B446 Gr. 2, which achieves minimum yield strength of 758 MPa. Always confirm ISO 15156-3 compliance documentation is available when fasteners will contact H₂S-containing media.
When evaluating suppliers, prioritize: (1) documented EN 10204 Type 3.1 or 3.2 mill certification on every order, (2) in-house PMI and hardness testing capability — not just reliance on mill certificates, (3) demonstrated export experience to your specific trade corridor with appropriate documentation, and (4) ISO 9001:2015 quality system certification. KK Fasteners meets all four criteria and offers third-party inspection coordination through SGS, BV, or TÜV for clients whose project specifications require independent verification.
Every Inconel 625 fastener order from KK Fasteners ships with full EN 10204 Type 3.1 mill traceability and in-house PMI verification — not as an optional upgrade, but as standard practice. If your project requires a material certification package, third-party inspection, or a custom dimensional specification, contact our technical team with your drawing or enquiry and we’ll provide a detailed quote within 24 hours.
