Nicorex Alloys is a certified ISO 9001 and ISO 14001 supplier and stockist of fasteners in Mumbai, India. We maintain fastener inventory in accordance with the required ASTM/ASME standards, from Hastelloy C276 and Inconel 625 to Super Duplex S32750 and Monel 400, in sizes from M6 to M100 (metric) and ¼” to 4” (imperial). We supply fasteners such as stud bolts, hex bolts, hex nuts, washers, threaded rods, socket head cap screws, U-bolts and anchor bolts in nickel alloy, duplex, super duplex and speciality steel grades.
A fastener is a hardware component that mechanically joins two or more parts. In process piping and pressure vessel service, stress corrosion cracking often strikes high-strength fasteners in chloride service. Selecting the correct nickel alloy grade ensures joint integrity and prevents sudden, catastrophic failures in offshore or chemical processing plants. Each type serves a different joint configuration, and the right choice depends on service environment, temperature, and corrosive media.
Fastener Material Grades
Hastelloy Fasteners
Inconel Fasteners
Incoloy Fasteners
Monel Fasteners
Nickel Fasteners
Duplex Steel Fasteners
Super Duplex Steel Fasteners
Fastener Specification
| Parameter | Details |
|---|---|
| Product | Stud Bolts, Hex Bolts, Hex Nuts, Washers, Threaded Rods, Socket Head Cap Screws, U-Bolts, Anchor Bolts |
| Dimensional Standards | ASME B18.2.1 (hex bolts), B18.2.2 (hex nuts), B18.3 (socket head), B18.21.1 (lock washers), B18.22.1 (plain washers) |
| Size Range | M6 to M100 (metric) / ¼” to 4” (imperial) |
| Length | 30 mm to 1000 mm+ (custom lengths available) |
| Thread | UNC, UNF, 8UN (≥1” per A193/A320), Metric coarse & fine per ISO 261 |
| Coating | Bare (standard), PTFE/Xylan coated, Hot-dip galvanised, Phosphate, Cadmium (on request) |
| Testing | Tensile, Proof Load (nuts), Hardness, PMI, Charpy (low-temp), NACE MR0175 |
| Standard | Scope | Grades Covered | Size Range | Service |
|---|---|---|---|---|
| ASTM F468/F468M | Non-ferrous bolts, hex cap screws, studs | Monel 400/K500, Inconel 625, Ni 200, C276, Cu-Ni | ¼”–1½” | General corrosion-resistant service |
| ASTM F467/F467M | Non-ferrous nuts | Same alloys as F468 | ¼”–1½” | Matching nuts for F468 bolts |
| ASTM F2281 | SS & Ni alloy bolts/studs, high-temp | N06625, N10276, N06022, N06600, N08825, etc. | ¼”–4” | High-temp corrosion-resistant |
| ASTM A1014 | PH Ni alloy bolting (718) | UNS N07718 only | ½”–4” | High-strength high-temp (turbine, subsea) |
| ASTM A1082 | PH & Duplex SS bolting | S31803, S32205, S32750, S32760, N09925 | ½”–4” | High-strength special purpose |
| ASTM A193 | Alloy steel & SS bolting, high-temp | B7 (4140), B8 (304), B8M (316), B16 (CrMoV) | ¼”–4”+ | Pressure vessels, valves, flanges |
| ASTM A194 | Nuts for high-pressure/temp bolts | Gr 2H, 4, 7, 8, 8M | ¼”–4”+ | Matching nuts for A193 bolts |
| ASTM A320 | Alloy steel & SS bolting, low-temp | L7, L7M, L43, B8, B8M | ¼”–4” | Cryogenic and low-temp service |
| ASTM A453 | High-temp bolting (expansion matching) | Gr 660 (A286) Class A/B/C/D | ¼”–4” | Austenitic flange bolting |
Fastener Standard: ASME / DIN / ISO / BS
Please refer to the table below for fastener standards across ASME, DIN, ISO, and BS industrial specifications.
| Product | ASME/ASTM | DIN | ISO | BS | Notes |
|---|---|---|---|---|---|
| Hex Bolt (full thread) | B18.2.1 | DIN 933 | ISO 4017 | BS 1768 | Full thread to head |
| Hex Bolt (partial thread) | B18.2.1 | DIN 931 | ISO 4014 | BS 1768 | Unthreaded grip length |
| Heavy Hex Bolt | B18.2.1 | – | – | – | Larger AF, US standard only |
| Stud Bolt (double-end) | B16.5 / A193 | DIN 938/939 | ISO 4734 | – | DIN 938 = equal thread both ends |
| Heavy Hex Nut | B18.2.2 | DIN 6915 | ISO 4033 | BS 1769 | Heavy series, flange bolting |
| Hex Nut (standard) | B18.2.2 | DIN 934 | ISO 4032 | BS 1768 | Normal height |
| Socket Head Cap Screw | B18.3 | DIN 912 | ISO 4762 | BS 4168 | Allen bolt |
| Flat Washer | B18.22.1 | DIN 125A | ISO 7089 | BS 4320A | Standard flat |
| Spring (Lock) Washer | B18.21.1 | DIN 127B | – | BS 4464 | Split ring |
| Threaded Rod | – | DIN 975 | ISO 4734 | – | Full-length threaded |
| U-Bolt | B18.31.5 | DIN 3570 | – | – | Pipe clamp type |
| Eye Bolt | – | DIN 444 / DIN 580 | ISO 3266 | BS 4278 | Lifting point |
| Set Screw (grub) | B18.3 | DIN 913/914/915/916 | ISO 4026–4029 | – | Various point types |
Fastener Thread Types
| Thread System | Standard | Designation | Use |
|---|---|---|---|
| UNC (Unified National Coarse) | ASME B1.1 | e.g., ¾”-10 UNC (10 TPI) | General purpose, most common in US/process piping |
| UNF (Unified National Fine) | ASME B1.1 | e.g., ¾”-16 UNF (16 TPI) | Higher tensile, aerospace, vibration-prone |
| 8UN (8-Thread Series) | ASME B1.1 | e.g., 1¼”-8UN (8 TPI) | Mandatory for ≥1” per ASTM A193/A320 |
| Metric Coarse | ISO 261/262 | e.g., M20 × 2.5 | Standard metric, most common globally |
| Metric Fine | ISO 261/262 | e.g., M20 × 1.5 | Higher tensile, precision |
| BSP (British Standard Pipe) | BS 21 | e.g., G½ | Pipe connections (not structural bolting) |
| Class | Tolerance | Use |
|---|---|---|
| 2A/2B (inch) | Standard | General-purpose bolting |
| 3A/3B (inch) | Tight | Aerospace, precision |
| 6g/6H (metric) | Standard | General purpose (equivalent to 2A/2B) |
Fastener Dimensions Chart
| Size | AF (mm) | AC (mm) | Head Height (mm) | Wrench Size |
|---|---|---|---|---|
| M10 | 17 | 19.6 | 6.63 | 17 mm |
| M12 | 19 | 21.9 | 7.76 | 19 mm |
| M16 | 24 | 27.7 | 10.18 | 24 mm |
| M20 | 30 | 34.6 | 12.72 | 30 mm |
| M24 | 36 | 41.6 | 15.26 | 36 mm |
| M30 | 46 | 53.1 | 18.7 | 46 mm |
| M36 | 55 | 63.5 | 22.5 | 55 mm |
| M42 | 65 | 75.1 | 26 | 65 mm |
| M48 | 75 | 86.6 | 30 | 75 mm |
| M56 | 85 | 98.1 | 35 | 85 mm |
| M64 | 95 | 109.7 | 40 | 95 mm |
| Size | AF (mm) | AC (mm) | Height (mm) | Wrench Size |
|---|---|---|---|---|
| M10 | 18 | 20.8 | 10.4 | 18 mm |
| M12 | 21 | 24.2 | 12.6 | 21 mm |
| M16 | 27 | 31.2 | 16.4 | 27 mm |
| M20 | 34 | 39.3 | 20 | 34 mm |
| M24 | 41 | 47.3 | 23.8 | 41 mm |
| M30 | 50 | 57.7 | 30.4 | 50 mm |
| M36 | 60 | 69.3 | 36.6 | 60 mm |
| M42 | 70 | 80.8 | 42 | 70 mm |
| M48 | 80 | 92.4 | 48 | 80 mm |
| M56 | 90 | 103.9 | 56 | 90 mm |
| M64 | 100 | 115.5 | 64 | 100 mm |
| Size | ID (mm) | OD (mm) | Thickness (mm) |
|---|---|---|---|
| M10 | 11 | 24 | 2.5 |
| M12 | 14 | 28 | 3.0 |
| M16 | 18 | 34 | 3.0 |
| M20 | 22 | 40 | 3.5 |
| M24 | 26 | 50 | 4.0 |
| M30 | 33 | 60 | 4.5 |
| M36 | 39 | 72 | 5.0 |
| M42 | 45 | 85 | 6.0 |
| M48 | 52 | 98 | 6.0 |
Get Fasteners at Competitive Prices
Types of Fasteners
Stud Bolt (Double-End Stud)
Strong hex nuts on dual-threaded headless rod. Most popular process piping flange joiner. For ASME B16.5 flanges, utilise 8UN thread for ≥1” diameter.
Hex Bolt
Hexagonal head on one end, threaded shank. Available fully or partially threaded per ASME B18.2.1 or ISO 4014/4017. Used for structural and equipment mounting.
Heavy Hex Nut
Internally threaded, heavy series (thicker and wider AF than standard). Standard for process piping flange bolting per ASME B18.2.2 and ASTM F467 (Ni alloy) or A194 (alloy steel).
Flat Washer
Undernut or bolt head, flat disc. Protects flange face and distributes clamping load. By ASME B18.22.1 or ISO 7089. Machined from bolt and nut alloy to prevent galvanic corrosion.
Spring Washer (Lock Washer)
Split-ring washer providing spring tension against vibration loosening. Per ASME B18.21.1. Many EPC specs now require Nord-Lock or Superbolt instead. Specify per project requirement.
Threaded Rod (All-Thread / Studding)
Fully threaded along its entire length. Supplied in 1 m, 2 m, and 3 m lengths. Cut to any stud bolt length on site. Same material specs as stud bolts (F468, A193).
Socket Head Cap Screw
Cylindrical head with internal hex (Allen) socket. Per ASME B18.3 / ISO 4762. Used in confined spaces where hex bolt wrench clearance is limited. Inconel 718 SHCS is widely used in aerospace.
Socket Head Cap Screw
U-shaped round bar threaded on both legs. Per ASME B18.31.5 / DIN 3570. Sized by pipe NPS. Used for clamping pipes to supports and hangers. Super Duplex and Inconel 625 U-bolts serve offshore pipe racks.
Anchor Bolt (J-Bolt, L-Bolt)
Anchored in concrete. J-bolt (hook end) and L-bolt (90° bend) cast-in-place. Per ACI 318/ASME B18.31.3. Chemical plant foundations use Hastelloy and Duplex anchor bolts.
Eye Bolt
Looped head for lifting and rigging. Per DIN 444 (plain eye) / DIN 580 (forged eye). WLL must be marked. Inconel 625 and Monel K500 eye bolts serve as offshore lifting points.
Hex Cap Screw
Hex head with a washer face and tighter tolerances than standard hex bolts. Per ASME B18.2.1. Used in tapped-hole applications without a separate nut.
NACE MR0175 / ISO 15156 Hardness Requirements for Fasteners
| Material | UNS | NACE Max Hardness | Condition | Notes |
|---|---|---|---|---|
| Inconel 625 | N06625 | HRC 35 max | Annealed | Most common Ni alloy fastener for sour |
| Inconel 718 | N07718 | HRC 40 max | Age hardened (restricted) | Per ISO 15156-3 Table A.32 |
| Hastelloy C276 | N10276 | HRC 35 max | Annealed | Sour + chloride resistance |
| Hastelloy C22 | N06022 | HRC 35 max | Annealed | Oxidising + reducing acid sour service |
| Monel K500 | N05500 | HRC 35 max | Age hardened (controlled) | Must control aging strictly |
| Monel 400 | N04400 | Not listed | Annealed | Removed from ISO 15156-3 in 2003; restricted to specific equipment per Table A.16 |
| Incoloy 825 | N08825 | HRC 35 max | Annealed | Sulfuric acid sour service |
| Incoloy 925 | N09925 | HRC 35 max | Age hardened (per NACE) | Subsea wellhead bolting |
| Duplex S31803/S32205 | S31803/S32205 | HRC 28 max | SA + quenched | Ferrite 35–65% governs per ISO 15156-3; HRC 28 is common project spec |
| Super Duplex S32750 | S32750 | HRC 32 max | SA + quenched | Ferrite 35–65% required; HRC 32 per industry practice |
| Super Duplex S32760 | S32760 | HRC 32 max | SA + quenched | Offshore sour; ferrite content governs per ISO 15156-3 |
| A193 B7M (4140) | — | HRC 22 max | Q&T with hardness control | NACE-compliant variant; plain B7 is NOT NACE-compliant |
| A453 Gr.660 (A286) | S66286 | HRC 35 max (Class D) | Double aged | High-temp sour service |
Industrial Applications of Fasteners
- Flanged Pipe Joints: Stud bolts, nuts, and washers for every flanged connection. Bolting must match flange grade to prevent galvanic corrosion and leak paths.
- Pressure Vessels and Heat Exchangers: Vessel lid, tubesheet, bonnet, and manway cover bolting in sizes up to M48 to M100. Inconel 625 for sour service, A453 Gr.660 for high-temp expansion matching.
- Oil and Gas: Subsea tree, wellhead flange, BOP, and riser connector bolting. Inconel 718 is used for HPHT, Incoloy 925 for NACE-qualified wellheads, and Super Duplex for topside. Per API 6A and API 20E.
- Chemical and Petrochemical Plants: Reactor, column flange, and heat exchanger bolts in acid service. Hastelloy C276 for mixed acid, Monel 400 for HF acid alkylation units.
- Power Generation and Nuclear: Turbine casing, boiler drum, and reactor vessel bolts. Inconel 718 is used for gas turbines, A453 Gr.660 for steam turbine flanges, and Inconel 600 for nuclear.
- Marine and Offshore Structures: Topside structural bolting, riser clamp bolts, pipe rack U-bolts. Monel K500 is used for subsea (non-magnetic), Super Duplex for structural, and Inconel 625 for splash zone.
- Aerospace and Defence: Engine mount, turbine disc, and airframe fasteners. Inconel 718 at 1240 MPa is the standard aerospace bolt grade. Socket head cap screws for confined engine spaces.
How to Order Fasteners from Nicorex Alloys
- Fastener type (stud, hex, nut, washer)
- Grade + UNS + ASTM spec
- Diameter and length in mm
- Thread type and class
- Quantity in pieces or sets
- Condition (annealed, aged, strain-hardened)
- Coating (bare, PTFE, silver, HDG)
- NACE/API compliance requirements
- Documentation (MTC 3.1, PMI, TPI)
- Packaging (oiled, VCI, heat-separated)
Stock items are dispatched in 2 to 3 days from Mumbai. Nicorex supplies pre-assembled flange bolt sets per ASME B16.5 bolt chart.
Related Products from Nicorex Alloys
Frequently Asked Questions
What is the Maximum Hardness for Nickel Alloy Bolts in Sour Service?
Can I Use Inconel 718 Bolts for Subsea Sour Service?
Yes, with restrictions per the ISO 15156-3 solution annealed + aged, HRC ≤40, and defined H₂S limits. This is not a blanket approval like that for Inconel 625. General subsea sour is safer with Inconel 625. High-strength HPHT requires 718 with a complete NACE qualification per API 20E.
Why do Nickel Alloy Bolts Gall During Tightening?
What is the Price of Fasteners in India?
What Documentation Comes with Every Fastener Shipment?
How to Select the Right Fastener Grade?
What is the formula to calculate the weight of fasteners?
Calculate stud weight using Weight = π/4 × D² × L × Density / 1,000. For alloys, multiply the base weight of carbon steel by the density multiplier.
Examples:
- Stud: M20 × 150mm (Carbon Steel) = 369g
- Alloy Stud: M30 × 250 mm (Monel 400) = 1,387 × 1.125 = 1,560g
- Nut: M24 Heavy Hex (Hastelloy C276) = 183 × 1.133 = 207g