The Hastelloy C276 hex bolt is a corrosion-resistant nickel-molybdenum-chromium fastener for chemical processing, pollution control, marine, oil and gas, and other aggressive-service assemblies. HASTELLOY® is a Haynes International trademark; the generic alloy designation is Alloy C-276, UNS N10276, also associated with Werkstoff 2.4819. For inch-series finished bolts, ASTM F468-23(2026) includes Alloy 276 / N10276, while ASTM B574-23 covers N10276 rod and bar. Hex-head geometry is specified separately, commonly to ASME B18.2.1 for inch products or ISO 4014/4017 for metric products.
Product Overview and Key Features
Alloy C-276 combines nickel with substantial molybdenum and chromium plus tungsten. It is selected primarily for resistance to severe corrosion rather than for the strength-class system used with carbon or alloy steel bolts.
- Ni-Cr-Mo-W alloy: UNS N10276 provides broad resistance to oxidizing and reducing corrosive environments.
- Localized-corrosion resistance: the alloy is recognized for resistance to pitting, crevice corrosion, and chloride-related stress-corrosion cracking.
- Uncoated service: corrosion resistance normally comes from the base alloy rather than zinc or sacrificial plating.
- Multiple dimensional systems: inch ASME and metric ISO hex-head geometries can be specified by drawing.
- Matching alloy hardware: ASTM F467 Alloy 276 nuts can be specified for compatible inch assemblies.
Hastelloy C276 Hex Bolt Specifications
Specification Overview
| Item | Specification / Common Requirement |
|---|---|
| Material | Alloy C-276 / UNS N10276 / Ni-Cr-Mo-W nickel alloy |
| Trademark name | HASTELLOY® C-276 when material is supplied under the Haynes trademark |
| Inch fastener material standard | ASTM F468-23(2026) Alloy 276 |
| Metric fastener material standard | ASTM F468M-06(2025) Alloy 276, when specified |
| Raw material reference | ASTM B574-23 for UNS N10276 rod and bar |
| Inch hex-bolt dimensions | ASME B18.2.1-2012 (R2021) |
| Metric dimensional options | ISO 4014:2022 partial-thread bolt or ISO 4017 full-thread screw, when ordered |
| Common inch thread | UNC or UNF to ASME B1.1 as specified |
| Common surface condition | Natural / uncoated alloy, cleaned or project-specified finish |
Common Inch Hex Bolt Dimensions
The table gives selected ASME B18.2.1 plain hex-bolt dimensions within the 1/4 to 1-1/2 inch ASTM F468 bolt range. s is basic width across flats, k is basic head height, and LT is nominal thread length for bolts 6 inches and shorter. These are dimensional references, not a Flybear stock matrix.
| Nominal Thread | UNC TPI | s Basic (in.) | k Basic (in.) | LT Nom. ≤6 in. (in.) |
|---|---|---|---|---|
| 1/4 | 20 | 7/16 | 11/64 | 0.75 |
| 3/8 | 16 | 9/16 | 1/4 | 1.00 |
| 1/2 | 13 | 3/4 | 11/32 | 1.25 |
| 5/8 | 11 | 15/16 | 27/64 | 1.50 |
| 3/4 | 10 | 1-1/8 | 1/2 | 1.75 |
| 1 | 8 | 1-1/2 | 43/64 | 2.25 |
| 1-1/4 | 7 | 1-7/8 | 27/32 | 2.75 |
| 1-1/2 | 6 | 2-1/4 | 1 | 3.25 |
When ASTM F468 Alloy 276 is specified, finished fasteners have a tensile-strength range of 110-140 ksi, minimum yield strength of 45 ksi, minimum elongation of 25%, and hardness range of 20-32 HRC. ASTM B574 raw-material compliance alone does not establish finished-bolt compliance.
Material, Surface Condition and Mating Hardware
Alloy C-276 Material
Typical C-276 composition is nickel balance with approximately 16% chromium, 16% molybdenum, 4% tungsten, and about 5% iron. Material certificates should identify UNS N10276 when that chemistry is required.
Finish and Lubrication Options
Natural, uncoated alloy is common because the corrosion performance comes from the nickel alloy itself. Cleaning, pickling, polishing, or project-specific lubricants may be requested. Coatings should only be applied when the joint specification calls for friction control, isolation, identification, or another defined purpose.
Matching Nuts and Galling Considerations
For inch ASTM assemblies, ASTM F467 Alloy 276 nuts provide a material-compatible option. Nickel-alloy threaded joints can gall under unfavorable assembly conditions, so lubricant, surface condition, tightening speed, thread fit, and approved torque procedure should be considered together.
Typical Applications and Selection Considerations
- Chemical reactors, heat exchangers, scrubbers, piping supports, and processing equipment.
- Pollution-control and waste-treatment systems exposed to aggressive chemical media.
- Marine, offshore, and chloride-bearing environments requiring resistance beyond conventional stainless steel.
- Oil and gas or sour-service equipment where the project specifically approves UNS N10276.
Buyers can review Flybear’s hex bolt versus hex cap screw guide before choosing ASME geometry, and the industry fastening solutions page for corrosion-critical applications. Final material selection must consider chemical concentration, temperature, load, mating material, and the applicable engineering code.
Ordering and Quality Documentation
An RFQ should state UNS N10276 / Alloy C-276, material specification, dimensional standard, diameter, thread series or pitch, length, partial or full thread, quantity, mating nut requirement, surface condition, lubricant, and documentation. Buyers may request chemical analysis, material certificates, tensile and hardness results, dimensional inspection, and thread gauging. Flybear’s quality control and inspection page outlines available inspection support; exact tests should be agreed for the order.
Frequently Asked Questions
Is Hastelloy C276 the same as UNS N10276?
HASTELLOY® C-276 is a Haynes trademark for Alloy C-276, while UNS N10276 is the generic Unified Numbering System designation. For multi-source procurement, identify UNS N10276 and the applicable ASTM specification.
Which ASTM standard applies to C276 hex bolts?
ASTM F468-23(2026) includes Alloy 276 / UNS N10276 for inch nonferrous bolts and hex cap screws used in general service. ASTM B574-23 covers N10276 rod and bar but should not replace finished-fastener requirements when F468 is specified.
Are metric C276 hex bolts available?
Metric Alloy C-276 fasteners can be specified to ASTM F468M where applicable, with a separate dimensional standard such as ISO 4014 or ISO 4017. Do not mix ASTM F468 inch dimensions with metric ISO geometry.
Does C276 require a protective coating?
Usually the alloy itself provides the corrosion resistance, so natural or cleaned C-276 is common. A coating or lubricant may still be specified for friction control, electrical isolation, identification, or another assembly requirement.
What should I include in a quotation request?
Provide material designation, governing standards, diameter, thread, length, thread length, quantity, matching hardware, finish, lubricant, operating environment, and required inspection documents. Include a drawing when nonstandard geometry or critical tolerances apply.
Request a Quote for Hastelloy C276 Hex Bolts
Send Flybear Industrial your Hastelloy C276 hex bolt diameter, length, thread, dimensional standard, UNS N10276 requirement, quantity, mating hardware, surface condition, and documentation needs. Include drawings for custom geometry or controlled chemical-service applications. Submit the details through the Flybear fastener RFQ page for technical review and quotation.
