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Monel 400 Seamless Pipe and Tube (SB-165, UNS N04400)
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Monel 400 is a nickel-copper alloy supplied as seamless pipe and tube under ASME SB-165 for UNS N04400. Its nominal 67/30 nickel-copper chemistry gives resistance to flowing sea water, steam, and alkalis, and it remains a reference material for marine, refinery, and chemical process installations.
Specification Coverage
SB-165 covers nickel-copper alloy UNS N04400 in the form of cold-worked seamless pipe and tube in the conditions shown in Table 1 and Table X1.1. Related forms are covered by SB-127 for plate, sheet and strip, SB-164 for rod, bar and wire, and SB-366 for factory-made wrought fittings; SB-564 covers forgings. Buyers should specify SB-165 explicitly when the purchasing specification references ASME Section II.
Grade Comparison
| Grade | UNS | Ni | Cu | Mo | Fe | Service Characteristic |
|---|---|---|---|---|---|---|
| Monel 400 | N04400 | 63.0 min | 28.0-34.0 | – | 2.5 max | General corrosion, seawater, alkali |
| Monel K-500 | N05500 | 63.0 min | 28.0-34.0 | – | 2.5 max | K-500 adds Al + Ti, age hardens |
| Nickel 200 | N02200 | 99.0 min | 0.25 max | – | 0.40 max | Pure nickel, caustic service |
| Inconel 625 | N06625 | 58.0 min | – | 8.0-10.0 | 5.0 max | Mo-rich, chloride pitting |
Monel 400 and Monel K-500 share the same nominal base chemistry. K-500 is aluminium and titanium stabilised and age-hardenable, giving higher strength and hardness where Monel 400 remains annealed and relatively soft. Monel 400 remains the correct selection for general corrosive duty where higher strength is not required and where the softer condition gives better resistance to stress corrosion cracking.
Chemical Composition (ASME SB-165 Table 2)
| Element | Max (%) | Variation from Max, max (%) |
|---|---|---|
| Nickel (by difference) | 63.0 min | 0.45 |
| Copper | 34.0 max | 0.20 |
| Iron | 2.5 max | 0.05 |
| Manganese | 2.0 max | 0.04 |
| Carbon | 0.3 max | 0.02 |
| Silicon | 0.5 max | 0.03 |
| Sulfur | 0.024 max | 0.005 |
Nickel shall be determined arithmetically by difference. The variation column gives the maximum permitted departure from the stated maximum when a product (check) analysis is performed by the purchaser.
Mechanical Properties (ASME SB-165 Table 1)
| Condition and Size | Tensile Strength min, psi (MPa) | Yield Strength (0.2% offset) min, psi (MPa) | Elongation in 2 in. or 50 mm (4D) min, % |
|---|---|---|---|
| Annealed, 5 in. (127 mm) OD and under | 70 000 (480) | 28 000 (195) | 35 |
| Annealed, over 5 in. (127 mm) OD | 70 000 (480) | 25 000 (170) | 35 |
| Stress-relieved, all sizes | 85 000 (585) | 55 000 (380) | 15 |
Tensile properties for small-diameter tube with specified wall thickness of 3 % or less of the specified outside diameter shall be in accordance with Table X1.1 of SB-165.
Size Range and Condition
SB-165 covers cold-worked seamless pipe and tube in annealed and stress-relieved conditions. Permissible variations for outside diameter and wall thickness are given in Table 3, and length variations for cut-to-length material in Table 4. Ends are plain cut and deburred. For small-diameter tube ordered to a specified wall thickness, the special diameter and wall tolerance provisions of Table X1.2 apply.
Applications
Monel 400 seamless pipe and tube are specified in seawater cooling and heat exchanger systems, fire-fighting water systems on offshore platforms, oil refinery sour-water and acid-handling units, pulp and paper processing equipment, and caustic and alkali service lines. Marine applications include piping to ISO 13680 and seawater systems covered by classification society rules, where resistance to flowing seawater and low galling tendency are the deciding factors.
Certification and Inspection
Each pipe or tube is subjected to either a hydrostatic test or a nondestructive electric test, with the choice of test at the manufacturer’s option unless otherwise specified on the purchase order. Material is supplied with a mill test certificate to ASME SB-165 including heat number, chemical analysis, mechanical properties, and dimensions. Supplementary requirements including eddy current testing, ultrasonic testing, and intergranular corrosion testing are available on request.
Ordering Information
For a quotation please specify: product form (seamless pipe or seamless tube), outside diameter and wall thickness or schedule, length and whether cut-to-length is required, delivery condition (annealed or stress-relieved), quantity, and destination port. State any additional testing, third-party inspection, or certification requirement. We will reply with availability, lead time, and FOB pricing ex Hefei, China.
Related specifications and products. Monel 400 is also supplied as butt weld fittings and as plate, sheet and strip. See nickel alloy round pipe and tube products Monel 400 butt weld fitting range Monel 400 plate, sheet and strip for the dimensional and material basis behind this page.
