Standards
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175 / ISO 15156-2
- NORSOK M-650 Qualified
- API 6A Certified
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 925 Hex Bolts (UNS N09925)
Integral hex-head bolts ASME B18.2.1 / ISO 4014 — sour-service NACE MR0175 stamped
Incoloy 925 hex bolts (UNS N09925) are single-piece fasteners with an integral hexagonal head and a partial- or fully-threaded shank, used with one nut to clamp two or more components together. The integral head distinguishes them from stud bolts (which are threaded at both ends and use two nuts) and from socket head cap screws (which use an internal hex drive). Hex bolts are the dominant fastener type for one-time structural connections, machinery assembly, valve bonnet bolting where the head is to remain installed, and bolted joints where the bolt rotates during make-up. TorqBolt manufactures Incoloy 925 hex bolts in sizes 1/4" to 2" diameter (M6 to M48 metric) ASME B18.2.1 / ISO 4014 dimensional standards, in the solution-annealed and aged condition (per heat-treatment specification) with 100% hardness inspection ensuring the 35 HRC NACE MR0175 sour-service cap. Every order ships with EN 10204 3.1 manufacturer's MTC documenting actual heat-lot chemistry, mechanical results and heat-treatment cycle vs ASTM B805 requirements; 3.2 with TPI witness on request.
Need Incoloy 925 hex bolts? Email info@torqbolt.com with diameter × length, thread reach (full or partial), thread series (UNC / UNF / metric), quantity, applicable standards (NACE MR0175 stamp, ASME B18.2.1 vs ISO 4014 head dimensions). WhatsApp +91-22-66157017.
Hex Bolt Designs Manufactured
| Design | Description | Standard | Typical Use |
|---|---|---|---|
| Hex bolt (partial thread) | Plain shank under head + threaded section at tip; thread length ASME B18.2.1 Table 11 | ASME B18.2.1 / ISO 4014 | Structural connections; bearings against the plain shank reduce shear |
| Hex bolt (fully threaded / tap bolt) | Threaded the entire length under head; same head as standard hex bolt | ASME B18.2.1 / ISO 4017 | Adjustable-grip joints; thin-flange bolting; tapped-hole connections |
| Heavy hex bolt | Larger across-flats hex head dimension than standard; thicker head | ASME B18.2.6 / heavy-hex-bolts page | High-load pressure-vessel bolting; flange joints requiring more wrench-engagement |
| Hex flange bolt | Integral flange (washer face) under hex head; eliminates separate washer | ASME B18.2.1 / EN 1665 | Vibration service; sheet-metal joining; low-clearance applications |
| Hex cap screw | Tighter dimensional tolerance than hex bolt; chamfered end + washer face | ASME B18.2.1 / ISO 4014 / hex-cap-screws page | Precision bolting; rotating-machinery service |
Standard Size Range & Thread Series
| Diameter | UNC (inch) | UNF (inch) | Metric Coarse (mm) | Across-Flats (AF) | Length Range |
|---|---|---|---|---|---|
| 1/4" / M6 | UNC 20 | UNF 28 | M6 × 1.0 | 7/16" / 10 mm | 16 to 100 mm |
| 5/16" / M8 | UNC 18 | UNF 24 | M8 × 1.25 | 1/2" / 13 mm | 20 to 120 mm |
| 3/8" / M10 | UNC 16 | UNF 24 | M10 × 1.5 | 9/16" / 17 mm | 20 to 150 mm |
| 7/16" / M12 | UNC 14 | UNF 20 | M12 × 1.75 | 5/8" / 19 mm | 25 to 200 mm |
| 1/2" / M14 | UNC 13 | UNF 20 | M14 × 2.0 | 3/4" / 22 mm | 25 to 250 mm |
| 9/16" / M16 | UNC 12 | UNF 18 | M16 × 2.0 | 13/16" / 24 mm | 30 to 300 mm |
| 5/8" / M18 | UNC 11 | UNF 18 | M18 × 2.5 | 15/16" / 27 mm | 35 to 350 mm |
| 3/4" / M20 | UNC 10 | UNF 16 | M20 × 2.5 | 1-1/8" / 30 mm | 40 to 400 mm |
| 7/8" / M22 | UNC 9 | UNF 14 | M22 × 2.5 | 1-5/16" / 32 mm | 45 to 450 mm |
| 1" / M24 | UNC 8 | UNF 12 | M24 × 3.0 | 1-1/2" / 36 mm | 50 to 500 mm |
| 1-1/8" / M30 | UNC 7 | UNF 12 | M30 × 3.5 | 1-11/16" / 46 mm | 60 to 500 mm |
| 1-1/4" / M33 | UNC 7 | UNF 12 | M33 × 3.5 | 1-7/8" / 50 mm | 65 to 500 mm |
| 1-3/8" / M36 | UNC 6 | UNF 12 | M36 × 4.0 | 2-1/16" / 55 mm | 70 to 500 mm |
| 1-1/2" / M39 | UNC 6 | UNF 12 | M39 × 4.0 | 2-1/4" / 60 mm | 75 to 500 mm |
| 1-3/4" / M45 | UNC 5 | M45 × 4.5 | 2-5/8" / 70 mm | 90 to 500 mm | |
| 2" / M48 | UNC 4.5 | M48 × 5.0 | 3" / 75 mm | 100 to 500 mm |
Head dimension standards differ: ASME B18.2.1 (inch series) and ISO 4014 (metric series) specify different across-flats (AF) dimensions for nominally-equivalent diameters, e.g., ASME 1/2" hex bolt = 3/4" AF, while ISO M14 = 22 mm AF. Specify the dimensional standard at RFQ stage so the wrench-engagement matches the customer's tool inventory.
Mechanical Property Requirements
| Property | Aged Condition (ASTM B805 min) |
|---|---|
| Tensile Strength | 165 ksi (1140 MPa) min |
| 0.2% Yield Strength | 110 ksi (760 MPa) min |
| Elongation in 4D | 18% min |
| Reduction of Area | 25% min |
| Hardness | 32–35 HRC (NACE sour-service cap) |
| Charpy V-notch at -46°C | 40 J min (NACE sour service) |
See full mechanical properties page for elevated-temperature data and Charpy envelope. Hex bolts are stamped on the head face with the heat number and standard reference ASME B18.2.1 marking provisions.
Applicable Standards
- ASTM B805, UNS N09925 forgings & forging stock (input bar / billet)
- ASME B18.2.1, Square, Hex, Heavy Hex, and Askew Head Bolts (inch-series dimensional)
- ASME B18.2.6, Fasteners for Use in Structural Applications (heavy hex variants)
- ISO 4014, Hexagon Head Bolts, Product Grades A and B (metric, partial thread)
- ISO 4017, Hexagon Head Screws, Product Grades A and B (metric, full thread)
- EN 1665, Hexagon Bolts with Flange (heavy series)
- ASTM A193 Grade B8N, Bolting Materials for High-Temperature or High-Pressure Service
- ASTM F2281, Standard Specification for Stainless Steel and Nickel-Alloy Bolts
- API 6A, Wellhead and Tree Equipment, when used as wellhead body or bonnet bolting
- NACE MR0175 / ISO 15156-3, Table A.10 sour-service qualification (35 HRC max)
- NORSOK M-630 MDS A30, Norwegian Continental Shelf bolting
- ASME B1.1 / B1.13M, thread tolerance and series (inch / metric)
- EN 10204 3.1 / 3.2, manufacturer / third-party witnessed certification
API 6A PSL Documentation Levels
| PSL | Pressure Class | Charpy Test Temperature | NDE Required |
|---|---|---|---|
| PSL-1 | 2,000–5,000 psi | Not required | Visual |
| PSL-2 | 5,000–10,000 psi | Not required | UT or MT (per heat lot) |
| PSL-3 | 10,000–15,000 psi | 27 J at -29°C (-20°F) | 100% UT |
| PSL-3G | 10,000–15,000 psi (gas / cryogenic) | 27 J at -46°C / -101°C | 100% UT + grain size |
| PSL-4 | 15,000–20,000 psi | 40 J at -46°C | 100% UT + 100% MT + TPI witness |
Manufacturing Sequence
- Bar input: Incoloy 925 round bar per ASTM B805 in the annealed condition. Bar diameter selected to give the head + shank dimensions after upset / machining.
- Head forging (cold or warm upset): Hex head formed by upset forging on a header press. The bar is fed into a die cavity and an axial force creates the integral hex profile. Cold upset preferred for diameters ≤1"; warm upset (~1500°F) for >1" to reduce die wear.
- Shank machining: Plain-shank diameter turned to nominal bolt size; chamfer applied at thread end ASME B18.2.1.
- Thread cutting / rolling: Threads applied in the SOLUTION-ANNEALED condition. Thread rolling preferred for ≤1-1/2" diameter (residual compressive stress at root improves fatigue life); single-point thread cutting for >1-1/2" or for special pitches.
- Solution anneal + age cycle: Per heat-treatment specification, 1900°F WQ + 1365°F × 8h FC + 1150°F × 8h AC. Head and shank both reach equilibrium during the 8-hour soak.
- Final inspection: Head dimensional check (across-flats, across-corners, head height) ASME B18.2.1; thread gauging Go / No-Go ASME B1.3; 100% Rockwell hardness per ASTM E18 (within 32–35 HRC); sample tensile + Charpy.
- Marking: Each bolt head stamped (low-stress die) with heat number, UNS N09925, applicable standard, NACE MR0175 stamp (sour orders), API 6A PSL level (wellhead orders).
Companion Components
- Incoloy 925 hex nuts, standard hex nuts ASME B18.2.2
- Heavy hex nuts, thicker / wider AF nuts for high-load joints
- Flat washers, load distribution under head + nut
- Spring washers / lock washers, vibration-loosening prevention (where allowed by code)
- Thread compound, sulphur-free, copper-free anti-seize per API RP 7A1 (Loctite 8009 nickel anti-seize)
Application Examples
- Pressure-vessel bonnet bolting: Where the bolt head must remain accessible from one side
- Pump casing bolts: Sour-service centrifugal pumps in oilfield production
- Compressor cylinder head bolts: Reciprocating sour-gas compressors
- Heat exchanger channel cover bolts: Sour-duty shell-and-tube exchangers
- Valve bonnet bolts (where bolt rotates during make-up): See surface safety valve internals
- Subsea connector bolting (one-time installation): Where studs are not preferred due to handling complexity
- Topside structural connections: Brackets, padeyes, j-tube clamps in marine service
- Refinery process piping: Sour-duty piping clamps, support brackets, instrument mounts
Standard Coatings & Finishes
- Bare (passivated): Per ASTM A380 / A967, standard sour-service finish
- PTFE coating: Xylan 1424 / 1070, low-friction make-up + wear protection on the head bearing surface
- Phosphate + oil: Manganese phosphate per MIL-DTL-16232 + light oil for storage protection
- Cad plate: NOT recommended for sour service (cadmium causes embrittlement of nickel alloys in H₂S)
- Hot-dip galvanise: NOT applicable (Incoloy 925 is corrosion-resistant; zinc adds galvanic risk)
Frequently Asked Questions
When should I use a hex bolt vs a stud bolt? Use a hex bolt when one side of the joint will not be accessible after assembly (the head sits on the inaccessible side and a single nut tightens from the accessible side), or when the bolt itself rotates during make-up (e.g., into a tapped hole). Use a stud bolt when both sides of the joint are accessible and the joint may need repeated disassembly, the same stud can be reused with new nuts. API 6A wellhead and Christmas tree bolting almost always uses studs; structural fasteners and machinery bolting more often use hex bolts.
What's the difference between a hex bolt and a hex cap screw? Dimensionally identical externally, but ASME B18.2.1 specifies tighter tolerance for hex cap screws (closer-toleranced head + shank dimensions, washer face under head, chamfered thread end). Hex cap screws are used for precision applications like rotating machinery; hex bolts for general structural use. See hex cap screws for the precision variant.
What head dimension standard do you supply, ASME or ISO? Both. Specify at RFQ stage. ASME B18.2.1 (inch series) gives across-flats dimensions like 3/4" for a 1/2" diameter bolt; ISO 4014 (metric series) gives 22 mm AF for a nominally-equivalent M14. The head dimensions are NOT interchangeable between standards even at apparently-similar diameters, specify the wrench-engagement requirement of your tool inventory.
Can hex bolts be supplied fully threaded (tap bolts)? Yes, the fully-threaded variant is ASME B18.2.1 (US) or ISO 4017 (metric). Used where the grip length is variable, where the bolt threads into a tapped hole rather than through a clearance hole + nut, or where the joint requires the maximum thread engagement length. Specify "tap bolt" or "fully threaded" at RFQ stage.
What thread compound for Incoloy 925 hex bolts? Sulphur-free, copper-free anti-seize per API RP 7A1: Loctite 8009 (high-purity nickel anti-seize), Henkel Permabond Antiseize 8023 (nickel-graphite-free), or PetroStar Premium Plus (PTFE-based). AVOID copper-bearing (galvanic), graphite-bearing (galvanic + sulfide-attracting), sulphur-bearing EP (SSC initiator) and zinc-bearing (hydrogen-charging during cathodic protection) compounds.
What's the typical lead time for Incoloy 925 hex bolts? Standard sizes (3/8" to 1" / M10 to M24, lengths to 200 mm): 4–6 weeks ex-bar-stock. Larger sizes (1-1/4" to 2" / M30 to M48): 6–8 weeks. Custom long lengths (above 300 mm) or high quantities (above 5,000 pieces): 8–10 weeks. The bottleneck is the 18-hour age cycle plus the head-upset operation, which requires a separate setup per diameter range.
Documentation Package
- EN 10204 3.1 manufacturer's MTC (3.2 with DNV / Bureau Veritas / Lloyd's / TUV / SGS witness on request)
- Heat-lot chemistry vs UNS N09925 limits ASTM B805
- Tensile + RA + elongation results per heat / per heat-treatment lot
- 100% hardness inspection per ASTM E18 (within 32–35 HRC NACE band)
- Charpy V-notch at -46°C / -101°C as applicable
- Heat-treatment furnace chart-recorder traces
- Head dimensional check ASME B18.2.1 / ISO 4014 (across-flats, across-corners, head height, washer-face diameter)
- Thread gauge inspection (Go / No-Go) ASME B1.3
- NACE MR0175 Table A.10 reference (sour-service orders)
- API 6A PSL level reference (wellhead orders) with TPI witness for PSL-4
- Bolt head marking: heat number + UNS N09925 + standard reference + NACE stamp
Related Products
- Hex nuts, standard hex nut companion ASME B18.2.2
- Heavy hex bolts, larger AF + thicker head variant
- Hex cap screws, precision hex bolt with washer face
- Stud bolts, both-end-threaded variant for repeated-disassembly joints
- Washers, flat / lock washer companions
- Full Incoloy 925 datasheet
Request a Quote
For Incoloy 925 hex bolts with full MTC documentation:
- Email: info@torqbolt.com
- Phone: +91-22-66157017
- WhatsApp: +91-22-66157017
Specify diameter, length, thread reach (partial / full / tap bolt), thread series (UNC / UNF / metric), head dimensional standard (ASME B18.2.1 / ISO 4014), quantity, applicable standards (API 6A PSL level, NACE MR0175 stamp, NORSOK MDS A30, ASTM A193 / F2281), required MTC level (3.1 / 3.2 with TPI witness) and any coating / finish requirement.
References: ASTM B805; ASTM A193 / F2281; ASME B18.2.1 (inch hex bolts); ASME B18.2.6 (heavy hex); ISO 4014 / 4017 (metric hex bolts / screws); EN 1665 (hex flange bolts); ASME B1.1 / B1.13M (thread series); ASME B1.3 (thread gauging); API Specification 6A Annex M; NACE MR0175 / ISO 15156-3 Table A.10; NORSOK M-630 / M-650; EN 10204; ASTM A380 / A967 (passivation); MIL-DTL-16232 (phosphate). Special Metals Corporation INCOLOY® alloy 925 Technical Bulletin. INCOLOY® is a registered trademark of Special Metals Corporation.
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