What Is a Seamless Monel K500 Tube?
Seamless Monel K500 Tube — UNS N05500 — is the precipitation-hardening member of the Monel family: the nickel–copper base of Monel 400 plus 2.30–3.15% aluminum and 0.35–0.85% titanium, specified to ASTM B865 and supplied seamless from a solid billet.
Controlled aging precipitates sub-microscopic gamma-prime Ni3(Al,Ti) particles throughout the matrix, lifting yield strength to roughly three times that of annealed Monel 400 while retaining the excellent corrosion resistance of the 400 base. K500 is also nonmagnetic down to about −100 °C. For cathodically protected hardware in seawater, hardness and strength should be capped — typically to 35 HRC per NACE MR0175 — to guard against hydrogen embrittlement.
Key Features and Advantages
Seamless UNS N05500 tube combines Monel 400 corrosion resistance with roughly tripled yield strength:
Precipitation Hardening by Gamma-Prime Ni3(Al,Ti): sub-microscopic particles formed during aging deliver the strength of a heat-treatable alloy inside a corrosion-resistant Ni-Cu matrix.
Approximately Three Times the Yield of Annealed Monel 400: 690 MPa (100 ksi) minimum yield in the aged condition versus 193 MPa (28 ksi) for annealed N04400.
Corrosion Resistance Equal to Monel 400: the base chemistry is unchanged, so seawater, HF and reducing-acid performance carries over.
Low Magnetic Permeability: essentially nonmagnetic down to about −100 °C in the aged condition, even at high strength.
Sour-Service Flexibility with Hardness Control: aging cycles can be tailored to keep hardness at or below 35 HRC for NACE MR0175 service.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for UNS N05500 seamless tube.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| N05500 | Monel K-500 | 2.4375 | NiCu30Al3Ti | Not listed in grade index | NS6500 / Ni68Cu28Al (legacy) |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
UNS N05500 seamless tube chemistry is tightly controlled so the corrosion and mechanical performance below is repeatable:
| Grade | Ni+Co | Cu | Al | Ti | Fe | Mn | C | Si | S |
|---|---|---|---|---|---|---|---|---|---|
| UNS N05500 | 63.0 min | 27.0–33.0 | 2.30–3.15 | 0.35–0.85 | ≤2.0 | ≤1.5 | ≤0.25 | ≤0.50 | ≤0.010 |
Chemical requirements per ASTM B865, Table 1 (Standard Specification for Precipitation-Hardening Nickel-Copper-Aluminum Alloy). K500 adds 2.30–3.15% aluminum and 0.35–0.85% titanium to the Monel 400 base; nickel is reported as Ni+Co minimum. Sulfur is held to 0.010% maximum.
Typical Mechanical Properties
Values below are specification minimums for the delivery condition; they define the acceptance basis for UNS N05500 seamless tube.
| Condition | Tensile Strength, min, ksi (MPa) | Yield Strength (0.2% Offset), min, ksi (MPa) | Elongation in 2 in. or 50 mm, min, % |
|---|---|---|---|
| Hot-finished and aged | 140 (965) | 100 (690) | 20 |
| Cold-drawn and aged | 145 (1000) | 105 (724) | 15 |
Mechanical properties per ASTM B865, Table 2, in the precipitation-hardened (aged) condition. Monel K500 has no dedicated ASTM seamless-tube product specification: chemistry follows B865 and dimensions follow the general requirements of ASTM B829-24, while tube mechanical properties are confirmed by agreement between manufacturer and purchaser against the B865 aged-condition minimums above. Values vary with section size and the applied aging cycle.
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably across a range of environments.
| Density | Melting Range | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity | Magnetic Permeability |
|---|---|---|---|---|---|---|
| 8.44 g/cm3 | 1315 – 1350 °C | 13.7 μm/m·°C (20–100°C) | 17.5 W/m·K (20°C) | 179 GPa | 0.615 μΩ·m (20°C) | < 1.0005 (200 Oe, aged) |
Size Tolerance Chart (mm)
Permissible variations for seamless nickel alloy tube in accordance with ASTM B829-24, Table 2:
| Nominal Outside Diameter, mm | Permissible Variation in OD, mm | Average Wall, % | Minimum Wall |
|---|---|---|---|
| 10.0 to 15.9, excl | ±0.13 | ±15 | +30% / −0 |
| 15.9 to 38.1, incl | ±0.19 | ±10 | +22% / −0 |
| over 38.1 to 76.2, incl | ±0.25 | ±10 | +22% / −0 |
| over 76.2 to 88.9, incl | ±0.38 | ±10 | +22% / −0 |
Notes (dimensions per ASTM B829-24, Table 2): tolerances apply to individual measurements and include ovality. For thin-wall tube (nominal wall 3% or less of the OD), the mean OD shall comply with the table and individual measurements are increased by 0.5% of the nominal OD. Wall variation in any cross section (eccentricity) shall not exceed ±10% of the actual average wall.
Length Tolerance
- When tube is ordered cut-to-length, length variation is +3.2 mm / −0 for OD under 50.8 mm and +4.8 mm / −0 for larger sizes (ASTM B829-24, Table 5); for lengths over 24 ft, an additional +3.2 mm per 10 ft applies, up to a maximum of +12.7 mm.
- Tube is normally supplied in mill lengths or specific cut lengths as agreed in the order.
Disclaimer: Dimensional data above are summarized from ASTM B829-24, Table 2. The full and most current specification documents must always be consulted for official design and procurement purposes.
Common Industrial Applications
The combination of corrosion resistance, mechanical strength and manufacturing quality makes UNS N05500 seamless tube a preferred choice for:
Pump Shafts and Valve Stems
High-strength rotating and trim components in seawater and chemical pump duty.
Oil-Well Tools and Downhole Equipment
Drill collars, instrument bodies and sour-gas components where strength plus corrosion resistance is required.
Springs, Fasteners and Machined Parts
Aged-condition springs, bolts and precision components for marine and chemical service.
Marine Propeller Shafts and Hardware
Shafting and fasteners combining seawater resistance with high fatigue strength.
Ordering Guide
When specifying UNS N05500 seamless tube, please include: quantity, outside diameter and wall (nominal or minimum), delivery condition, length, and any third-party inspection or supplementary requirements — our sales team will confirm the production schedule and send a formal quotation.
Frequently Asked Questions
What sizes are available for Monel K500 seamless tube?
The overall range is OD 6–257 mm; WT 0.5–35 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs Monel K500 seamless tube?
ASTM B865 / ASME SB865 is the governing specification for Monel K500 seamless tube. The edition in force at order time is stated on the quotation and purchase order; chemistry, mechanical properties, heat treatment, dimensions and testing are reported against the ordered standard and material heat.
What inspection documents are provided?
Each order is documented with a mill test certificate stating heat chemistry and mechanical test results. EN 10204 3.1 certification, hydrostatic testing, eddy-current or ultrasonic inspection and PMI are performed when specified in the purchase order.
Ready to Request a Quotation?
Send the NPS and schedule (or actual OD and wall), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
