Monel K500
Fasteners
UNS N05500
Monel K500 — When Monel 400 Strength Is Not Enough
Both Monel 400 (UNS N04400) and Monel K500 (UNS N05500) are nickel-copper alloys with identical seawater and HF acid corrosion immunity. The critical difference is mechanical strength. Monel K500 is produced by adding aluminium (2.30–3.15%) and titanium (0.35–0.85%) to the Monel 400 Ni-Cu base, then applying a two-stage heat treatment — solution anneal at 980°C followed by age hardening at 593°C. The resulting Ni₃(Al,Ti) gamma-prime precipitate raises tensile strength to ≥1000 MPa with ≥690 MPa yield — more than three times the strength of annealed Monel 400.
For fastener engineering, this means K500 is specified when bolt load calculations require strength beyond ≥480 MPa (Monel 400) — specifically for ASME B16.5 Class 1500/2500 pressure flanges, subsea wellhead bolting, FPSO riser clamps, offshore structural connections, and high-pressure marine pump flanges where high bolt load and permanent seawater corrosion immunity must be achieved simultaneously. K500 delivers strength equivalent to Grade 8.8 carbon steel bolts with Ni-Cu alloy corrosion immunity that no stainless steel grade can replicate in seawater and HF acid environments.
NACE MR0175 hardness limit (≤35 HRC) for H₂S sour service is met by the age-hardened condition. All K500 fasteners from Akbar Fasteners carry NABL-accredited Rockwell HRC test reports confirming compliance. Matched K500 stud bolts, hex nuts, and washers from the same ASTM B865 certified heat are available — single MTC, single PMI, single COC for the complete assembly.
| Element | Min % | Max % | Typical |
|---|---|---|---|
| Nickel + Cobalt | 63.0 | — | ~65% |
| Copper (Cu) | — | Balance | ~30% |
| Aluminium (Al) | 2.30 | 3.15 | ~2.7% |
| Titanium (Ti) | 0.35 | 0.85 | ~0.6% |
| Iron (Fe) | — | 2.0 | ~1.5% |
| Manganese (Mn) | — | 1.5 | — |
| Carbon (C) | — | 0.25 | — |
| Silicon (Si) | — | 0.50 | — |
Monel K500 Fasteners — All Product Forms
All product forms manufactured from ASTM B865 certified UNS N05500 bar stock, age-hardened, PMI-verified. Complete matched sets from the same heat — one MTC, one PMI, one COC for the assembly.
K500 Stud Bolts
Fully threaded and double-end. Class 150–2500. M12–M100, lengths to 3,000mm. The primary K500 fastener for ASME B16.5 pressure flanges in seawater and HF acid service. Heavy hex nuts from same heat on request.
View Stud Bolts →K500 Hex Bolts
Full thread (DIN 933), partial thread (DIN 931), heavy hex (ASME B18.2.3.6M). M6–M100. For offshore equipment covers, marine structural connections, and seawater pump flanges requiring K500’s high-strength corrosion immunity.
View Hex Bolts →K500 Hex Nuts
Standard hex (DIN 934), heavy hex (ASME B18.2.2), and coupling nuts (DIN 6334) in age-hardened K500. M6–M100. Matched material from same ASTM B865 heat eliminates galvanic risk in seawater and offshore service.
View Hex Nuts →K500 Washers
Plain flat (DIN 125 A/B) and spring helical (DIN 127) in age-hardened K500. M5–M100. Same-heat as stud bolts for matched assembly — zero galvanic corrosion at bearing face in seawater, offshore, and HF acid service.
View Washers →K500 Threaded Rods
Full thread DIN 975 and end-thread DIN 976. M6–M100, lengths to 3,000mm. For marine hanger systems, offshore equipment support tie-rods, and structural systems in seawater splash zones requiring K500’s high-strength immunity.
View Threaded Rods →Socket Cap Screws
Hex socket cylindrical head for confined-access marine equipment bolting. M4–M36. Used in seawater pump internals, subsea instrument enclosures, and offshore equipment where hex head clearance is unavailable in corrosive service.
View All Forms →Matched Assembly Sets
Stud bolts + heavy hex nuts + flat washers from same certified UNS N05500 heat. One mill test certificate, one PMI XRF report, one COC covering the complete flanged joint assembly. Simplifies TPI hold plan documentation for offshore and subsea EPC projects.
Request Matched Set →Custom Configurations
Left-hand thread, inch UNC/UNF, non-standard diameters, proprietary head forms, and drawing-specific K500 fasteners. Naval vessel hardware, offshore structural, minesweeper hull fittings, and bespoke marine equipment. Send drawing to sales@akbarfasteners.in.
Send Drawing →Why Engineers Specify Monel K500 Over Monel 400
3× the Bolt Load Capacity
≥1000 MPa UTS versus ≥480 MPa for Monel 400 — same Ni-Cu alloy chemistry and identical seawater and HF acid corrosion immunity, but three times the allowable bolt load from the age-hardening heat treatment cycle. Mandatory for ASME B16.5 Class 1500 and Class 2500 flanges, FPSO riser clamps, and subsea wellhead bolting where Monel 400 is structurally insufficient.
NACE MR0175 Sour Service Compliance
Age-hardened K500 at ≤35 HRC complies with NACE MR0175 / ISO 15156 for H₂S sour service — Akbar Fasteners supplies NABL-accredited Rockwell HRC certificates with every order confirming compliance. Monel K500 delivers the higher strength required for offshore high-pressure sour gas joints while meeting the NACE hardness limit that no austenitic stainless steel high-strength bolt achieves.
Inherently Non-Magnetic
Monel K500 is non-magnetic in the age-hardened condition — a critical specification for minesweeper hull fittings, naval compass binnacle hardware, and marine electronic equipment structural connections where ferromagnetic fasteners cannot be used regardless of corrosion resistance requirements. AMS 4676 specification covers naval procurement.
Single MTC — Complete Assembly
Stud bolts, nuts, and washers from the same certified UNS N05500 heat carry one mill test certificate, one PMI XRF report, and one COC — eliminating the multi-document vendor package required when sourcing fastener components from different suppliers. Critical for offshore project TPI hold plan efficiency and EPC vendor document submission.
Standards We Manufacture & Test To
Same quality system as our Hastelloy B3 stud bolts and complete exotic alloy range. Full heat traceability from mill certificate to dispatch.
Industry Applications
High-strength bolting in permanently corrosive marine environments — where ≥1000 MPa bolt load and permanent seawater or HF acid immunity must be achieved simultaneously.
Offshore Platforms
Class 1500/2500 flanges
Subsea Equipment
subsea manifold flanges
Desalination Plants
Class 900+ pump flanges
HF Alkylation Units
HF acid Class 600+ joints
Oil & Gas
NACE MR0175 assemblies
Naval & Defence
minesweeper hardware
Marine Pumps
high-pressure flange bolts
Power Generation
Class 600+ cooling systems
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · HRC · Charpy
TÜV · BV · Lloyds
Compare Monel Grades & Alloy Alternatives
K500 for high-strength seawater service. Monel 400 for lower-load marine applications. Hastelloy for acid service.
ASTM B865 K500 Overview
Full Monel K500 product range under ASTM B865 — composition, heat treatment, all product forms, and documentation package details at a glance.
View Page →Monel 400 Fasteners
Annealed Ni-Cu for lower bolt-load marine applications. ≥480 MPa UTS — same seawater and HF acid immunity as K500 at lower cost when design bolt loads permit Monel 400.
View Page →Hastelloy B3 Stud Bolts
For reducing HCl and strongly reducing acid environments — the specification where Monel K500 is insufficient for the corrosion environment and HCl-specific Ni-Mo alloy is needed.
View Page →Hastelloy Fasteners India
Complete Hastelloy range — six grades for mixed acid, chlorinated, and reducing acid service where Monel alloys are not the specification. All forms from Mumbai.
View Range →Need Monel K500
Fasteners Now?
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