Unifit Fastener manufactures and supplies Inconel 625 Fasteners (UNS N06625 / WNR 2.4856) for demanding industrial applications where high corrosion resistance, mechanical performance, and reliable material traceability are required. Our range includes hex bolts, heavy hex bolts, stud bolts, nuts, socket cap screws, washers, threaded rods, and custom fasteners, subject to product and size availability.
Inconel 625 fasteners are specified for marine, offshore, subsea and chemical processing service because the alloy's 8-10% molybdenum and 3.15-4.15% niobium content gives a PREN of approximately 50, and because it resists chloride stress corrosion cracking in service where 316L and duplex bolting are crevice-attacked. Unlike age-hardened nickel alloys, annealed 625 is not susceptible to hydrogen embrittlement under cathodic protection, which is why it is used for subsea bolting. We supply fasteners in customer-specified sizes, thread configurations, and requirements, with applicable manufacturing and inspection options based on the product specification.
Every consignment ships with an EN 10204 3.1 material test certificate showing heat number, chemical analysis and mechanical results. 3.2 certification and third-party inspection by SGS, TÜV, BV or Lloyd's are available on project specification. For broader material selection, explore our Inconel Fasteners range, or contact our team for a 625-specific requirement.
To quote, send us: fastener type, diameter and length, thread specification, quantity, governing standard (ASTM F468 / F467 or DIN), any additional testing (IGC per ASTM G28 Method A, PMI, UT), and delivery port. We return a priced offer with lead time within one working day.
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Inconel 625 Fastener Product Range
Unifit Fastener supplies Alloy 625 bolts, nuts, washers, screws, threaded rods, and studs for critical assemblies in offshore, marine, chemical, aerospace, and power generation environments.
Inconel 625 Bolts
Inconel 625 Nuts
Inconel 625 Washers
Inconel 625 Screws
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Technical Data
Inconel 625 Fastener Specifications: ASTM F468, F467 and B446
| Attribute | Detail |
|---|---|
| Grade / Alloy | Inconel 625, Alloy 625 |
| UNS Number | N06625 |
| Werkstoff No. | 2.4856 |
| Bolt / screw / stud standard | ASTM F468 / F468M |
| Nut standard | ASTM F467 / F467M |
| Bar and rod stock | ASTM B446 / ASME SB-446 (Grade 1 annealed, Grade 2 solution annealed) |
| Forged fastener stock | ASTM B564 / ASME SB-564 |
| Aerospace | AMS 5666 |
| British | BS 3076 NA21 |
| Thread standards | ASME B1.1 (UNC/UNF), ASME B1.13M (metric M profile) |
| Dimensional standards | ASME B18.2.1, B18.2.2, DIN 931 / 933 / 934, ISO 4014 / 4017 / 4032 |
| Size range | M3 to M100; 1/8" to 4" (custom sizes to specification) |
| Material condition | Annealed (Grade 1) or solution annealed (Grade 2) — specify on enquiry |
| Max hardness | 35 HRC (as required by NACE MR0175 / ISO 15156 for sour service) |
Inconel 625 Chemical Composition (UNS N06625)
| Element | Symbol | Content (%) |
|---|---|---|
| Nickel | Ni | 58.0 min |
| Chromium | Cr | 20.0 - 23.0 |
| Molybdenum | Mo | 8.0 - 10.0 |
| Niobium + Tantalum | Nb + Ta | 3.15 - 4.15 |
| Iron | Fe | 5.0 max |
| Carbon | C | 0.10 max |
| Manganese | Mn | 0.50 max |
| Silicon | Si | 0.50 max |
| Sulfur | S | 0.015 max |
| Phosphorus | P | 0.015 max |
| Aluminum | Al | 0.40 max |
| Titanium | Ti | 0.40 max |
| Cobalt | Co | 1.00 max |
Composition limits per ASTM B446 / ASME SB-446. The molybdenum and niobium content is what distinguishes 625 from 600 and 601, and is the reason the alloy resists pitting and chloride stress corrosion cracking. Actual heat analysis is reported on the EN 10204 3.1 certificate.
Inconel 625 Fastener Mechanical Properties
| Property | Grade 1 (annealed) | Grade 2 (solution annealed) |
|---|---|---|
| Tensile strength, min | 827 MPa (120 ksi) | 690 MPa (100 ksi) |
| Yield strength 0.2% offset, min | 414 MPa (60 ksi) | 276 MPa (40 ksi) |
| Elongation in 2 in. / 50 mm, min | 30% | 30% |
| Typical hardness | Up to 35 HRC max for sour service per NACE MR0175 | Up to 35 HRC max for sour service per NACE MR0175 |
Caption to sit under the table: Values are specification minima per ASTM B446 / ASME SB-446. Typical annealed bar results are approximately 930 MPa tensile and 517 MPa yield. Certified results for your heat are stated on the EN 10204 3.1 MTC supplied with each consignment.
Physical Properties of Inconel 625 (UNS N06625)
| Property | Unit | Value |
|---|---|---|
| Density | g/cm³ | 8.44 |
| Density | lb/in³ | 0.305 |
| Melting Range | °F | 2350–2460 |
| Melting Range | °C | 1290–1350 |
| Curie Temperature | °C | Below -196 |
| Relative Permeability | - | 1.0006 (measured at 15.9 kA/m) |
| Modulus of Elasticity | GPa | 207 |
Inconel 625 Fasteners International Equivalent Standards
| Standard Body | Designation |
|---|---|
| UNS (American) | N06625 |
| Werkstoff Nr. (German/European) | 2.4856 |
| AFNOR (French) | NC22DNB4M |
| JIS (Japanese) | NCF 625 |
| BS (English) | NA 21 |
| GOST (Russian) | XH75MBTIO |
| EN | NiCr22Mo9Nb |
| Trade Names | Altemp 625, Chronin 625, Nickelvac 625 |
Inconel 625 Bolt Torque Chart
| Bolt Diameter | Threads per Inch (TPI) | Dry Torque (ft-lb) | Lubricated Torque (ft-lb) |
|---|---|---|---|
| 1/4" | 20 - 28 | 7.8 - 8.9 | 5.8 - 6.6 |
| 5/16" | 18 - 24 | 15.9 - 17.6 | 12.0 - 13.2 |
| 3/8" | 16 - 24 | 28.2 - 32.0 | 21.2 - 23.9 |
| 7/16" | 14 - 20 | 45.1 - 50.4 | 33.9 - 37.8 |
| 1/2" | 13 - 20 | 68.8 - 77.6 | 51.6 - 58.2 |
| 9/16" | 12 - 18 | 99.2 - 110.8 | 74.5 - 83.1 |
| 5/8" | 11 - 18 | 137.0 - 155.2 | 102.8 - 116.4 |
| 3/4" | 10 - 16 | 244 - 271 | 183 - 204 |
| 7/8" | 9 - 14 | 392 - 433 | 294 - 324 |
| 1" | 8 - 14 | 588 - 659 | 441 - 495 |
| 1-1/4" | 7 - 12 | 1024 - 1133 | 767 - 849 |
| 1-1/2" | 6 - 12 | 1780 - 2003 | 1335 - 1502 |
Where Are Inconel 625 Fasteners Used?
Inconel 625 fasteners are the material of choice across demanding industrial sectors where standard stainless steel or carbon steel fasteners fail.
| Industry | Specific Application |
|---|---|
| Offshore Oil and Gas | Wellhead assemblies, subsea manifolds, riser clamps, BOP systems |
| Chemical Processing | Reactor vessels, heat exchanger flanges, acid-handling pipelines |
| Aerospace and Defense | Engine exhaust mounts, airframe structural fasteners, nacelle hardware |
| Marine and Naval | Propeller shaft bolting, seawater intake systems, hull penetrations |
| Nuclear Power | Reactor coolant system bolts, control rod mechanisms, containment structures |
| Power Generation | Gas turbine combustion liners, steam generator connections, boiler hardware |
| Desalination Plants | Evaporator vessel closures, pump casing fasteners, brine heater connections |
| Pharmaceutical / Food | Sanitary fittings in CIP/SIP systems requiring full corrosion resistance |
| Cryogenic Applications | LNG plant bolting, cold box connections, cryogenic valve assemblies |
| Pulp and Paper | Digester bolting, bleach plant equipment, recovery boiler attachments |
Inconel 625 vs Inconel 718 vs 316L Fasteners: Selection Comparison
| Property | Inconel 625 | Inconel 718 | SS 316L |
|---|---|---|---|
| UNS No. | N06625 | N07718 | S31603 |
| Condition compared | Annealed (ASTM B446 Gr 1) | Solution treated + aged (ASTM B637) | Annealed (ASTM A193 B8M Cl.1) |
| Tensile strength, min | 827 MPa | 1276 MPa | 515 MPa |
| Yield strength, min | 414 MPa | 1034 MPa | 205 MPa |
| Typical tensile (annealed bar) | 930 MPa | 1375 MPa | 550 MPa |
| PREN (approx.) | 50 | 30 | 25 |
| Chloride SCC resistance | Excellent | Good | Poor — susceptible above approx. 60°C |
| Seawater / subsea bolting | Suitable, including under cathodic protection | Restricted — hydrogen embrittlement risk under CP; see API 20E / 20F and DNV guidance | Not recommended for stagnant or warm seawater — pitting and crevice attack |
| Sour service (NACE MR0175) | Acceptable, annealed, 35 HRC max | Acceptable within stated limits and hardness caps | Acceptable within stated limits |
| Relative cost | High | Highest | Low |
| Typical use | Offshore, subsea, chemical processing, flue gas desulphurisation | Aerospace, high-strength downhole and rotating components | General corrosion service, food, pharma |
Minimum values are specification minima for the stated product form and condition. Typical values are indicative annealed bar results and are not guaranteed. PREN is calculated as Cr + 3.3Mo + 16N and is used for comparison only. Confirm all values against the certified MTC for the supplied heat.
Quality, Inspection & Documentation
Inconel 625 Fasteners can be supplied with quality documentation and inspection records according to the applicable product specification and customer requirements. Available documentation and inspection options may include:
| Quality / Inspection Item | Details |
|---|---|
| Material Test Certificate (MTC) | EN 10204 3.1 / 3.2, where specified and confirmed |
| Material Identification | Positive Material Identification (PMI), where required |
| Dimensional Inspection | Verification of dimensions, thread details and applicable tolerances |
| Mechanical Testing | Hardness and tensile testing, where required by the applicable specification |
| Corrosion / NDT | Corrosion testing and applicable non-destructive testing available on request, subject to specification |
| Third-Party Inspection | Available where required by the customer or purchase specification, subject to confirmation |
| Traceability | Heat/batch and material traceability documentation, where supported by the applicable supply and quality system |
Certifications and Quality Standards
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality management system for manufacturing and supply |
| EN 10204 3.1 / 3.2 | Material test certificates with applicable chemical and mechanical data |
| NACE MR0175 / ISO 15156 | Sour service supply — UNS N06625 in the annealed condition, 35 HRC maximum, within the environmental limits stated in Part 3 |
| ASME BPVC Section II Part B (SB-446 / SB-564) | Material specifications for Alloy 625 bar and forgings used in code construction |
| AMS 5666 | Aerospace specification for applicable Inconel 625 products |
| Third-Party Inspection | Available as required according to customer and project specifications |
| ASTM F468 / F467 | Product specifications for nonferrous bolts, screws, studs and nuts, including UNS N06625. |
| PED 2014/68/EU | where the client actually holds it. Two of the four top-ranking competitors display PED approval. If Unifit holds it, add it; if not, do not. |
Surface Finishes for Inconel 625 Fasteners
| Surface Finish | Typical Application |
|---|---|
| Mill Finish | General mechanical and industrial applications |
| Polished Finish | Pharmaceutical, food processing, and applications requiring a smoother surface |
| Brushed Finish | Marine and architectural applications |
| Passivated Finish | Chemical processing, food and pharmaceutical service where a clean, oxide-free surface is required |
| Phosphating | General industrial applications where specified |
| Xylan / PTFE Coating | Anti-galling and controlled-friction service. Recommended for all 625 stud-and-nut assemblies — nickel alloys gall severely when assembled dry, and the coating also lowers the friction factor used in torque calculation. |
Machining of UNS N06625 Threaded Studs
| Parameter | Ipr (lpr) | Mm/rev | fpm | m/min |
|---|---|---|---|---|
| Surface Speed / Feed | 0.005-0.020 | 0.13-0.51 | 13-35 | 4.0-10.7 |
Inconel 625 work-hardens rapidly during machining. Use sharp, coated carbide or CBN tooling, high coolant flow, and avoid dwelling or rubbing to prevent surface hardening that impairs subsequent operations.
Test Methods for Alloy 625 Studs
| Alloy / Product | Test Methods |
|---|---|
| Inconel 625 Fasteners | E38 (Chemical Analysis), E76 (Nickel Alloys), E354 |
| Additional Mechanical Tests | ASTM E8 Tensile, E10 Brinell, E18 Rockwell, E92 Vickers |
| Corrosion Tests | ASTM G28 IGC, G46 Pitting, G61 Crevice Corrosion |
| Non-Destructive Tests | ASME Section V - UT, RT, MT, PT as applicable |
DIN / ISO Standards for Inconel 625 Fasteners
Inconel 625 fasteners can be supplied in different product forms manufactured to applicable DIN and ISO dimensional standards, subject to the required product type, dimensions, and customer specifications.
| Product Type | Applicable DIN / ISO Standards | Typical Product Forms |
|---|---|---|
| Bolts | DIN 931, DIN 933, ISO 4014, ISO 4017 | Hex Bolts / Hex Head Screws |
| Nuts | DIN 934, ISO 4032 | Hex Nuts |
| Washers | As per confirmed DIN / ISO standard | Flat / Plain Washers |
| Screws | As per confirmed DIN / ISO standard | Machine / Socket / Custom Screws |
ASTM / ASME Standards: Applicable ASTM and ASME references should be specified according to the fastener type, material requirements, and customer specification after technical validation.
Commercial Availability & Delivery
| Buyer Information | Details |
|---|---|
| Common Stock Items | Commonly requested Inconel 625 bolts, nuts, stud bolts and other fastener forms may be available from stock |
| Made-to-Order Sizes | Custom diameters, lengths, thread configurations and fastener forms can be manufactured to specification |
| MOQ | Minimum order quantity depends on product type, size, material condition and manufacturing requirements |
| Standard Lead Time | Lead time for standard/regular requirements depends on stock availability and order quantity |
| Custom Lead Time | Custom or made-to-order fasteners require lead time based on drawings, specifications, quantity and manufacturing route |
| Urgent Dispatch | Expedited or urgent dispatch may be available for selected stock items, subject to availability and order confirmation |
| Export Documentation | Export orders can be supplied with applicable commercial and shipping documents, including packing list, commercial invoice and certificate of origin |
How Unifit Manufactures Inconel 625 Fasteners
Step 1: Raw Material Sourcing
We source bar stock, wire, and forgings from approved mills with documented heat and chemical analysis.
Step 2: Forming / Forging
Fasteners are produced via hot forging (M24-M100), cold forging (M3-M24), or CNC precision machining depending on geometry and size.
Step 3: Threading
Threads are rolled or single-point cut to ASME B1.1 (UNC/UNF) and ASME B1.13M (metric) tolerance classes, typically 2A/6g unless the customer specifies otherwise. Threads are rolled after final annealing so the compressive residual stress at the root is retained in the finished part.
Step 4: Surface Treatment
Finished fasteners are pickled and passivated to ASTM B600 for nickel alloys — not ASTM A967, which applies to stainless steels — then polished or coated to specification: phosphating, HDG, black oxide, Xylan 1070 or PTFE. Anti-galling coating is recommended on 625 nut-and-bolt assemblies, which gall readily when run dry
Step 5: Testing and Inspection
- Dimensional inspection: CMM / calibrated go-no-go gauges
- Hardness testing to ASTM E18 (Rockwell) or E10 (Brinell), with results held at 35 HRC maximum where NACE MR0175 / ISO 15156 sour service applies
- Tensile, yield and elongation testing to ASTM E8 / E8M, reported against the ASTM B446 minima for the supplied grade and condition
- Intergranular corrosion testing to ASTM G28 Method A (the applicable IGC test for nickel-chromium-molybdenum alloys)
- Ultrasonic / Radiographic testing on request
- Third-party inspection from SGS, TUV, BV, and Lloyds
Step 6: Marking and Packing
All fasteners are stamped or marked with grade, standard, heat number, and manufacturer code. Packing is provided in wooden cases, pallets, or carton boxes with moisture barriers for export.
Full Inspection Capabilities at Unifit Fastener
- Hardness Test (Rockwell HRB/HRC, Brinell)
- Flattening Test
- Pitting Resistance Test
- Chemical Analysis via Spectroscopy (OES/XRF)
- Intergranular Corrosion (IGC) Test
- Positive Material Identification (PMI) - 100% per heat
- Flaring Test
- Micro and Macro Structural Analysis
- Stress Rupture Testing
- Microstructure Testing
Inconel 625 Fastener Weight Calculator
Estimate consignment weight for freight quotation and inventory planning. Select fastener type, thread size and length to calculate approximate weight per piece and per 100 pieces, based on an Alloy 625 density of 8.44 g/cm³.
Formula (round stock, per piece): Weight (kg) = (π / 4) × D² × L × ρ ÷ 1,000,000, where D = diameter in mm, L = length in mm, and ρ = density in g/cm³ (8.44 for Inconel 625).
Density used: Inconel 625 (UNS N06625) — 8.44 g/cm³ / 0.305 lb/in³.
Packing and Delivery
Inconel 625 fasteners are packed for export in VCI-coated polyethylene bags, bundled by size and heat, and loaded into ISPM-15 fumigated wooden crates or pallets with desiccant for sea and air freight.
Lead Time and Delivery Schedule
- We maintain ready stock of standard Inconel fasteners to support urgent project requirements.
- Standard stock items: typically dispatched within 2-5 business days.
- Custom sizes and non-standard specifications: generally supplied within 2-4 weeks, depending on manufacturing requirements.
- Actual delivery schedules may vary depending on quantity, product specification, testing requirements, and destination country.
Export Capability
Unifit Fastener supplies Inconel 625 fasteners to customers in over 50 countries, with regular shipments to the UAE, Saudi Arabia, Qatar, Germany, the USA, Singapore, Australia and South Africa, and other regions. We provide complete export documentation, material test certificates (MTC), and third-party inspection reports upon request.
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FAQ's About Inconel 625 Fasteners
What industries use Inconel 625 fasteners?
They are widely used in aerospace, marine, offshore platforms, chemical processing, nuclear, and high-temperature applications.
Are Inconel 625 fasteners resistant to corrosion?
Yes, they resist pitting, crevice corrosion, and chloride-induced stress corrosion cracking, making them ideal for marine and chemical environments.
What is the melting range of Inconel 625?
Inconel 625 has a melting range of 1290-1350°C, making it suitable for extreme-temperature industrial applications.
Are custom thread pitches available for Inconel 625 fasteners?
Yes, custom threads can be manufactured to meet specific industrial requirements, including metric and imperial standards.
What is the main difference between Inconel 625 and Inconel 825?
Inconel 625 offers higher strength and excellent resistance to chloride and seawater corrosion, while Inconel 825 is primarily selected for resistance to a wide range of acids and chemical environments.