Monel K500
Hex Bolts
UNS N05500
Why Monel K500 for Hex Bolts
Monel K500 (UNS N05500) 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 3× the strength of annealed Monel 400 — while retaining the Ni-Cu alloy’s permanent immunity to seawater, HF acid, and chloride-induced stress corrosion cracking.
For hex bolts in marine, offshore, and chemical plant applications, this means a single alloy delivers what would otherwise require two separate materials: high tensile bolting strength (matching alloy steel grade 8.8) and complete seawater corrosion immunity (matching or exceeding the best stainless grades in chloride service). K500 hex bolts in seawater pump flanges, marine heat exchanger covers, and offshore platform deck equipment show no measurable corrosion after years of service where 316L stainless would pit and seize within months. For reducing acid environments where K500 is not specified, see our Hastelloy B3 stud bolts.
Akbar Fasteners Pvt. Ltd. machines K500 hex bolts from ASTM B865 certified UNS N05500 bar stock, XRF PMI-verifies every lot on receipt against the mill certificate, and dispatches with NABL-accredited mechanical test reports. Matching K500 heavy hex nuts and K500 washers supplied from the same heat on request.
| 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 | — |
| Sulfur (S) | — | 0.010 | — |
| Ultimate Tensile Strength | ≥ 1000 MPa |
| 0.2% Proof Stress (YS) | ≥ 690 MPa |
| Elongation | ≥ 20% |
| Hardness | ≤ 35 HRC |
| Heat Treatment | Age Hardened |
Full Thread Hex Bolts (DIN 933)
Thread runs the complete length from head to end — standard specification for bolted connections through through-holes in flanges and structural members. DIN 933 / ISO 4017 dimensions. The most common K500 bolt for marine seawater pump flanges, offshore platform deck connections, and desalination equipment covers. Available M6–M100 in standard metric pitch. Matched K500 hex nuts from same heat supplied on request.
Compared to our K500 stud bolts, full thread hex bolts are preferred when the joint must be assembled and disassembled regularly from one side, and where tapped holes or through-holes are used rather than flanged pressure joints.
| Spec | Details |
|---|---|
| Material | UNS N05500 / Monel K500 |
| Standard | ASTM B865 · DIN 933 · ISO 4017 |
| Size Range | M6 — M100 |
| Thread | Metric coarse DIN 13 |
| Head | Hex per DIN 933 AF |
| UTS | ≥ 1000 MPa |
| 0.2% YS | ≥ 690 MPa |
| Elongation | ≥ 20% |
| Hardness | ≤ 35 HRC |
| Condition | Age Hardened |
Partial Thread Hex Bolts (DIN 931)
DIN 931 / ISO 4014 — threaded end with a plain (unthreaded) shank between head and thread start. Standard for structural bolted joints where the shank carries shear load across the joint interface. The unthreaded shank also prevents thread engagement into the bearing material of the connected member, which is required in many structural design standards. M6–M100.
Partial thread K500 bolts are common in marine platform structural connections, offshore crane pedestals, and equipment skid base bolting in seawater splash zones where both shear capacity and corrosion immunity are required simultaneously.
| Spec | Details |
|---|---|
| Material | UNS N05500 / Monel K500 |
| Standard | ASTM B865 · DIN 931 · ISO 4014 |
| Size Range | M6 — M100 |
| Shank | Plain (unthreaded) per DIN 931 |
| Thread Length | Per DIN 931 grip length |
| UTS | ≥ 1000 MPa |
| 0.2% YS | ≥ 690 MPa |
| Condition | Age Hardened |
Heavy Hex Bolts (ASME B18.2.3.6M)
ASME B18.2.3.6M heavy hex bolts have wider across-flats and greater head height than DIN 933 — providing increased wrench bearing area for high-torque tightening and greater head strength at elevated temperatures. Specified alongside K500 heavy hex nuts for ASME B16.5 pipe flange connections in Class 150–2500 where stud bolts are not required. M12–M100.
Heavy hex K500 bolts are the standard for large seawater pump casings, HF alkylation unit flanged covers, and desalination plant heat exchanger bonnets — applications requiring high torque capacity combined with seawater and acid corrosion immunity.
| Spec | Details |
|---|---|
| Material | UNS N05500 / Monel K500 |
| Standard | ASTM B865 · ASME B18.2.3.6M |
| Size Range | M12 — M100 |
| Head | Heavy Hex — wider AF, greater height |
| Thread | Full thread or partial thread |
| UTS | ≥ 1000 MPa |
| Nuts | Matched K500 Heavy Hex Nuts |
| Condition | Age Hardened |
Flanged Hex Bolts
Hex bolts with an integrated flange (washer face) under the head — eliminates the need for a separate washer, distributes bearing load over a larger area, and prevents the bolt head from pulling into soft material. Standard per DIN 6921 or ISO 4162. M6–M64.
K500 flanged hex bolts are used in marine GRP (fibreglass) structure bolting, composite hull fitting connections, and equipment bases on soft substrates in seawater environments — where the integrated flange prevents pull-through without requiring a separate K500 washer.
| Spec | Details |
|---|---|
| Material | UNS N05500 / Monel K500 |
| Standard | ASTM B865 · DIN 6921 · ISO 4162 |
| Size Range | M6 — M64 |
| Head | Hex with integral serrated flange |
| Thread | Full thread standard |
| UTS | ≥ 1000 MPa |
| Condition | Age Hardened |
Inch Thread Hex Bolts (UNC / UNF)
Monel K500 hex bolts in UNC (coarse) and UNF (fine) thread forms per ASME B1.1. Head dimensions per ASME B18.2.1 or B18.2.3.1M. ¼”–4″ diameter. For US offshore, naval, and export projects specified in imperial dimensions where metric is not used.
Same ASTM B865 certified UNS N05500 age-hardened material — identical corrosion resistance and mechanical properties. Full thread and partial thread (hex cap screw) available. Supply with matched inch thread K500 nuts from same heat on request.
| Spec | Details |
|---|---|
| Material | UNS N05500 / Monel K500 |
| Standard | ASTM B865 · ASME B18.2.1 |
| Size Range | ¼” — 4″ |
| Thread | UNC · UNF per ASME B1.1 |
| Head | Hex per ASME B18.2.1 AF |
| UTS | ≥ 1000 MPa |
| Condition | Age Hardened |
DIN 931 / DIN 933 Hex Bolt Dimensions — UNS N05500
Standard dimensions per DIN 931/933 and ISO 4014/4017. All sizes in mm. Partial thread shank length (b) per DIN 931 grip length formula. Custom lengths and non-standard sizes to sales@akbarfasteners.in.
| Size (M) | Thread Pitch | AF (s) mm | Head Height (k) mm | Full Thread (DIN 933) | Part Thread b (DIN 931) | Heavy Hex AF mm | Condition |
|---|---|---|---|---|---|---|---|
| METRIC HEX BOLTS — UNS N05500 · ASTM B865 · AGE HARDENED | |||||||
| M6 | 1.0 mm | 10.0 | 4.0 | 10–100 mm | 18 mm | — | Age Hard. |
| M8 | 1.25 mm | 13.0 | 5.3 | 12–200 mm | 22 mm | — | Age Hard. |
| M10 | 1.5 mm | 17.0 | 6.4 | 16–200 mm | 26 mm | — | Age Hard. |
| M12 | 1.75 mm | 19.0 | 7.5 | 20–300 mm | 30 mm | 21.0 | Age Hard. |
| M16 | 2.0 mm | 24.0 | 10.0 | 30–300 mm | 38 mm | 26.9 | Age Hard. |
| M20 | 2.5 mm | 30.0 | 12.5 | 40–300 mm | 46 mm | 33.5 | Age Hard. |
| M24 | 3.0 mm | 36.0 | 15.0 | 50–300 mm | 54 mm | 40.4 | Age Hard. |
| M30 | 3.5 mm | 46.0 | 18.7 | 60–300 mm | 66 mm | 50.8 | Age Hard. |
| M36 | 4.0 mm | 55.0 | 22.5 | 70–300 mm | 78 mm | 60.3 | Age Hard. |
| M42 | 4.5 mm | 65.0 | 26.0 | 80–300 mm | 90 mm | 71.0 | Age Hard. |
| M48 | 5.0 mm | 75.0 | 30.0 | On order | On order | 82.6 | Age Hard. |
| M56 – M100 | 5.5–6.0 mm | Custom | Custom | On order | On order | Custom | Age Hard. |
* Non-standard lengths, fine pitch metric (DIN 13 fine), UNC/UNF inch thread on request. Send drawing to sales@akbarfasteners.in
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.
Monel K500 Bolt Applications
Wherever you need the seawater corrosion resistance of Monel combined with bolt-grade strength — K500 hex bolts are the specification that delivers both without compromise.
Marine & Offshore
equipment skid bases
Seawater Pump Flanges
impeller body bolts
Desalination Plants
vessel nozzle bolts
Oil & Gas
wellhead cover bolts
HF Alkylation Units
HF acid flanges
Naval & Defence
minesweeper structure
GRP / Composite
marine composite joints
Power Generation
condenser cover bolts
Complete Documentation Package
Heat & Lot Traceable
Conformance
100% Lots Verified
Tensile · Hardness
TÜV · BV · Lloyds
Matched Monel K500 Assembly Components
Order bolts, nuts, washers, and stud bolts together from the same certified UNS N05500 heat — one documentation package, zero galvanic risk in the assembly.
Monel K500 Nuts
Standard hex, heavy hex, and coupling nuts in age-hardened K500. Same certified heat as these bolts — identical alloy, no galvanic couple.
View Page →Monel K500 Washers
Plain flat and spring washers in K500. M5–M100. Complete the assembly with matched material washers — eliminate all galvanic corrosion at the joint.
View Page →Monel K500 Stud Bolts
Fully threaded stud bolts, Class 150–2500, M12–M100 up to 3,000mm. For pressure flange joints where stud bolts are preferred over hex bolts.
View Page →Monel 400 Fasteners
Annealed Ni-Cu for lower-strength marine applications. Same seawater resistance as K500 at lower cost when bolt loads don’t require age-hardened strength.
View Page →Need Monel K500
Hex Bolts Now?
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