The Monel K500 hex head bolt is a precipitation-hardened nickel-copper fastener for marine, offshore, chemical-processing, pump, valve, and oilfield assemblies requiring higher strength than Monel 400. MONEL® is a registered trademark of the Special Metals Corporation group of companies; the generic designation is Alloy K-500, UNS N05500, also associated with W.Nr. 2.4375. ASTM F468-23(2026) includes Alloy 500 for inch finished fasteners, while ASTM F468M-06(2025) covers metric products from M6 to M36. Hex-head geometry is specified separately.
Product Overview and Key Features
Alloy K-500 adds aluminum and titanium to a nickel-copper base and develops higher strength through precipitation hardening.
- Age-hardened nickel-copper alloy: solution treatment and aging develop significantly higher strength than annealed Monel 400.
- Marine-service capability: K-500 is widely used for fasteners, shafts, springs, pumps, valves, and other components exposed to seawater and marine environments.
- High finished-fastener strength: ASTM F468 Alloy 500 specifies a 130 ksi minimum tensile strength for covered inch sizes.
- Multiple dimensional systems: ASME B18.2.1 can define inch hex-bolt geometry, while ISO 4014 or ISO 4017 may be specified for metric products.
- Matching alloy hardware: ASTM F467 Alloy 500 nuts are available for compatible inch-series assemblies.
Monel K500 Hex Head Bolt Specifications
Specification Overview
| Item | Specification / Common Requirement |
|---|---|
| Material | Alloy K-500 / UNS N05500 / W.Nr. 2.4375 |
| Alloy family | Precipitation-hardenable nickel-copper-aluminum-titanium alloy |
| Current inch fastener standard | ASTM F468-23(2026), Alloy 500 |
| Current metric fastener standard | ASTM F468M-06(2025), Alloy 500 |
| Raw material reference | ASTM B865-25 for UNS N05500 bar, rod, wire, forgings, and forging stock |
| Inch dimensional reference | ASME B18.2.1-2012 (R2021) hex bolt geometry |
| Metric dimensional options | ISO 4014 partial thread or ISO 4017 full thread, when specified |
| Common inch thread forms | UNC or UNF to ASME B1.1 |
| Common surface condition | Natural / uncoated alloy; project-specified lubricant where required |
Selected Inch Hex Bolt Dimensions
The table shows selected ASME B18.2.1 plain hex-bolt dimensions within the ASTM F468 range. s is basic width across flats and k is basic head height. Thread length depends on diameter and bolt length.
| Nominal Thread | UNC TPI | s Basic (in.) | k Basic (in.) |
|---|---|---|---|
| 1/4-20 | 20 | 7/16 | 11/64 |
| 3/8-16 | 16 | 9/16 | 1/4 |
| 1/2-13 | 13 | 3/4 | 11/32 |
| 5/8-11 | 11 | 15/16 | 27/64 |
| 3/4-10 | 10 | 1-1/8 | 1/2 |
| 7/8-9 | 9 | 1-5/16 | 37/64 |
| 1-8 | 8 | 1-1/2 | 43/64 |
| 1-1/4-7 | 7 | 1-7/8 | 27/32 |
| 1-1/2-6 | 6 | 2-1/4 | 1 |
ASTM F468 Alloy 500 fasteners from 1/4 through 7/8 inch have 130-180 ksi tensile strength, 90 ksi minimum yield strength, and 24-37 HRC hardness. For 1 through 1-1/2 inch, tensile strength remains 130-180 ksi while minimum yield strength is 85 ksi. Minimum elongation for machined specimens is 20%.
Material, Heat Treatment and Surface Condition
Alloy K-500 Material
UNS N05500 contains 63-70% nickel, copper as the balance element, 2.30-3.15% aluminum, and 0.35-0.85% titanium, with controlled residual elements. Aluminum and titanium enable precipitation hardening while preserving nickel-copper corrosion behavior.
Heat Treatment and Strength Condition
ASTM F468 Alloy 500 fasteners are solution annealed and aged. ASTM B865 covers N05500 mill products, but raw-material compliance alone does not establish finished-fastener compliance. State the finished-bolt standard when mechanical properties are controlled.
Finish and Lubrication Options
Natural or cleaned K-500 is common because corrosion resistance comes from the alloy. Zinc plating is not normally required. Project-specific anti-seize or lubricant may control friction and thread damage. Confirm compatibility with process fluid and mating hardware.
Typical Applications and Selection Considerations
- Marine pumps, valves, shafts, propeller-related equipment, and seawater handling systems.
- Oil and gas valves, well tools, instrumentation, and offshore equipment.
- Chemical-processing pumps, valve components, and corrosion-resistant machinery.
- Industrial assemblies requiring greater strength than Monel 400 with similar nickel-copper corrosion behavior.
Flybear’s hex bolt versus hex cap screw guide explains why geometry and material should be specified separately. Buyers can also review industry fastening solutions for marine, oil and gas, and fluid-system applications. Final selection should consider exposure, temperature, stress, mating material, and design requirements.
Ordering and Quality Documentation
An RFQ should identify UNS N05500 / Alloy K-500, ASTM F468 or F468M when required, dimensional standard, diameter, thread, length, partial or full thread, quantity, mating nut, surface condition, lubricant, and documentation. Buyers may request chemical analysis, heat-treatment records, tensile and yield results, hardness, dimensional inspection, and thread gauging. Flybear’s quality control and inspection page describes available inspection support; exact records should be agreed before production.
Frequently Asked Questions
Is Monel K-500 the same as UNS N05500?
MONEL® K-500 is the trademarked alloy name, while UNS N05500 is the generic material designation. For multi-source procurement, specify UNS N05500 together with the applicable finished-fastener and dimensional standards.
How is Monel K-500 different from Monel 400?
K-500 is based on the nickel-copper chemistry of Monel 400 but adds aluminum and titanium so it can be precipitation hardened. This produces substantially higher strength and hardness while retaining much of the corrosion resistance associated with Monel 400.
Which ASTM standard applies to K-500 hex bolts?
ASTM F468-23(2026) covers inch nonferrous bolts, hex cap screws, socket head cap screws, and studs and includes Alloy 500 / N05500. ASTM F468M-06(2025) is the metric companion covering M6 through M36.
What nuts should be paired with K-500 bolts?
ASTM F467 Alloy 500 nuts provide a compatible inch-series option. For metric assemblies, ASTM F467M covers matching nonferrous nuts. The nut proof strength, thread, geometry, and surface condition should match the specified bolt assembly.
What information should I include in a quotation?
Provide material designation, finished-fastener standard, dimensional standard, diameter, thread series or pitch, length, thread length, quantity, matching hardware, surface condition, lubricant, operating environment, and inspection requirements. Include a drawing for special geometry.
Request a Quote for Monel K500 Hex Head Bolts
Send Flybear Industrial your Monel K500 hex head bolt diameter, length, thread, dimensional standard, UNS N05500 requirement, quantity, mating hardware, surface condition, lubricant, and documentation needs. Include drawings for custom geometry or controlled marine and process-service applications. Submit the details through the Flybear fastener RFQ page for technical review and quotation.
