Hastelloy C276
Bolts
UNS N10276
Why C276 Has the Highest Molybdenum in Its Class
Hastelloy C276 (UNS N10276) was engineered to solve the single most common problem in corrosion-resistant bolt selection: the alloy that resists oxidising acids often fails in reducing acids, and vice versa. C276 resolves this by combining 15–17% molybdenum — the highest Mo content in any commercial Ni-Cr-Mo alloy — with 14.5–16.5% Cr and 3–4.5% W to provide simultaneous protection across both oxidising and reducing media.
Molybdenum is the key element for reducing acid resistance (HCl, H₂SO₄). Chromium is the key element for oxidising acid resistance (HNO₃, hypochlorite). C276 has enough of both to perform across the full spectrum — unlike C22 which optimises for oxidising chloride at the expense of reducing acid resistance, and unlike B3 which optimises for reducing acids at the expense of oxidising resistance. For chemical plant that handles both — or where the process fluid composition varies — C276 bolts provide the only single-alloy solution.
For bolted connections specifically: C276’s ultra-low carbon (≤0.010%) and silicon (≤0.08%) prevent sensitisation at weld heat-affected zones, making C276 bolts the correct choice when the bolt sits adjacent to a welded structure in corrosive service — even if the weld was made without heat treatment. Matched C276 hex nuts and C276 washers from same certified heat on request.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel (Ni) | Balance | — | ~57% |
| Molybdenum (Mo) | 15.0 | 17.0 | ~16% |
| Chromium (Cr) | 14.5 | 16.5 | ~15.5% |
| Tungsten (W) | 3.0 | 4.5 | ~4% |
| Iron (Fe) | 4.0 | 7.0 | ~5.5% |
| Cobalt (Co) | — | 2.5 | — |
| Carbon (C) | — | 0.010 | — |
| Silicon (Si) | — | 0.08 | — |
| Vanadium (V) | — | 0.35 | — |
Choose the Right Hastelloy Grade for Your Bolt Application
Use this matrix to select the correct Hastelloy grade for your specific corrosion environment. Akbar Fasteners Pvt. Ltd. supplies all three grades as hex bolts, stud bolts, nuts, and washers from ISO 9001:2015 certified Mumbai facility.
| Corrosion Environment | C276 (N10276) This Page | C22 (N06022) | B3 (N10675) |
|---|---|---|---|
| Mixed / Unknown Acid Media | ✔ Best Choice | Acceptable | Not Ideal |
| Oxidising Acids (HNO₃, HClO₄) | Good | ✔ Best Choice | Avoid |
| Oxidising Chloride / FGD Service | Good | ✔ Best Choice | Avoid |
| Reducing HCl (all concentrations) | Moderate | Poor | ✔ Best Choice |
| Dilute H₂SO₄ (reducing) | Good | Moderate | ✔ Best Choice |
| Chlorinated Solvents / Wet Cl₂ | ✔ Best Choice | Good | Avoid |
| Seawater (all temperatures) | Excellent | ✔ Excellent | Good |
| Hypochlorite / Bleach | Good | ✔ Best Choice | Avoid |
| NACE H₂S Sour Service | ✔ Compliant | ✔ Compliant | Check hardness |
| Phosphoric Acid (H₃PO₄) | ✔ Excellent | Good | Moderate |
| Organic Acids (acetic, formic) | ✔ Excellent | Good | Good |
| Multipurpose / Variable Media | ✔ Best Choice | Limited range | Limited range |
Need grade selection advice? Contact sales@akbarfasteners.in — our technical team specifies the correct Hastelloy grade for your process conditions.
Hastelloy C276 Bolt Types & Applications
All forms machined from ASTM B574 certified UNS N10276 solution-annealed bar. PMI-verified before production. Matched C276 nuts and washers from same heat on request.
Full Thread Hex Bolts
Thread runs complete length. Standard for chemical reactor access covers, agitated vessel body bolts, heat exchanger channel head bolts, and multipurpose process equipment closures in mixed or undefined acid environments. M6–M100. Most common C276 bolt form for general chemical plant service.
Partial Thread Hex Bolts
Unthreaded plain shank carries shear load across joint — required for chemical plant structural connections, equipment skid base bolts, and reactor support structure bolting in mixed acid splash zones where shear capacity and broad corrosion resistance are both needed. M6–M100.
Heavy Hex Bolts
Wider across-flats and greater head height than DIN 933 — for high-torque tightening on large chemical reactor covers, agitated vessel covers, and large-diameter equipment access flanges in mixed acid service. Matched C276 heavy hex nuts from same ASTM B574 certified heat. M12–M100.
Flanged Hex Bolts
Integrated flange (washer face) under head — eliminates the need for a separate C276 washer while distributing bearing load. Used in FRP-lined vessel nozzle connections, composite equipment covers, and chemical plant connections through soft substrates in mixed acid environments. M6–M64.
Socket Cap Screws
Cylindrical hex-socket head for confined-access bolting — chemical reactor internals, agitator blade attachment, heat exchanger internal baffle fastening, instrument flange bolting, and sampling port closures in mixed acid and chlorinated solvent service environments. Allen key drive. M4–M48.
Inch Thread UNC / UNF
UNC (coarse) and UNF (fine) thread for US chemical plant, pharmaceutical, and offshore projects in imperial dimensions. ¼”–4″. Same ASTM B574 certified UNS N10276 solution-annealed material. Matched inch-thread C276 nuts from same heat. For US EPC project procurement where metric is not specified.
DIN 931 / DIN 933 C276 Hex Bolt Dimensions
Standard dimensions per DIN 931/933. All in mm. For flanged pressure joints see our C276 stud bolt ASME B16.5 dimension table. Non-standard and fine pitch on request to sales@akbarfasteners.in.
| Size (M) | Pitch | AF (s) mm | Head Ht (k) mm | Full Thread (DIN 933) | Part Thread b (DIN 931) | Heavy Hex AF mm | Condition |
|---|---|---|---|---|---|---|---|
| METRIC HEX BOLTS — UNS N10276 · ASTM B574 · SOLUTION ANNEALED · PRE≈66 | |||||||
| M6 | 1.0 mm | 10.0 | 4.0 | 10–100 mm | 18 mm | — | Sol. Ann. |
| M8 | 1.25 mm | 13.0 | 5.3 | 12–200 mm | 22 mm | — | Sol. Ann. |
| M10 | 1.5 mm | 17.0 | 6.4 | 16–200 mm | 26 mm | — | Sol. Ann. |
| M12 | 1.75 mm | 19.0 | 7.5 | 20–300 mm | 30 mm | 21.0 | Sol. Ann. |
| M16 | 2.0 mm | 24.0 | 10.0 | 30–300 mm | 38 mm | 26.9 | Sol. Ann. |
| M20 | 2.5 mm | 30.0 | 12.5 | 40–300 mm | 46 mm | 33.5 | Sol. Ann. |
| M24 | 3.0 mm | 36.0 | 15.0 | 50–300 mm | 54 mm | 40.4 | Sol. Ann. |
| M30 | 3.5 mm | 46.0 | 18.7 | 60–300 mm | 66 mm | 50.8 | Sol. Ann. |
| M36 | 4.0 mm | 55.0 | 22.5 | 70–300 mm | 78 mm | 60.3 | Sol. Ann. |
| M42 | 4.5 mm | 65.0 | 26.0 | On order | On order | 71.0 | Sol. Ann. |
| M48 | 5.0 mm | 75.0 | 30.0 | On order | On order | 82.6 | Sol. Ann. |
| M56–M100 | 5.5–6.0 | Custom | Custom | On order | On order | Custom | Sol. Ann. |
* Fine pitch metric, UNC/UNF inch — sales@akbarfasteners.in
Standards We Manufacture & Test To
Same quality system as our Hastelloy B3 stud bolts and complete ASTM B574 Hastelloy fastener range. Full heat traceability throughout.
Industry Applications
C276’s dual coverage of oxidising and reducing media makes it the standard choice for any plant where process streams change, mix, or are not definitively characterised.
Multipurpose Chemical Plant
campaign-change reactors
Oil & Gas
chemical injection systems
Offshore Platforms
seawater + acid service
Desalination
mixed media stages
Pulp & Paper
bleach plant connections
Pharmaceutical
variable media reactors
FGD Scrubbers
wet SO₂ + chloride service
Waste Treatment
chlorinated scrubber bolts
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Related C276 & Hastelloy Products
Same-heat C276 stud bolts, washers, and competing grade alternatives — all from one certified source.
Hastelloy C276 Stud Bolts
ASME B16.5 fully threaded and equal-end stud bolts for pressure flange joints. Class 150–2500, M12–M100, lengths to 3,000mm. Matched heavy hex nuts same heat.
View Page →Hastelloy C276 Washers
Plain flat, spring, and large OD washers in C276 from same certified heat — matched alloy throughout the assembly, zero galvanic risk in mixed acid service.
View Page →Hastelloy C22 Stud Bolts
For FGD and oxidising chloride service — C22’s 22% Cr gives superior pitting resistance over C276 when oxidising chloride is the sole concern.
View Page →Hastelloy B3 Stud Bolts
For reducing HCl service — B3’s high Mo without Cr gives near-zero corrosion in HCl at all concentrations where C276 shows moderate resistance.
View Page →Need Hastelloy C276
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