Which ASTM and ASME Standards Cover Alloy 400 Pipe?
Alloy 400, designated UNS N04400, is a nickel-copper alloy that is ordered to different specifications depending on the product form and the method of manufacture. The documents that appear most often on mill certificates are listed below.
ASTM B165 - seamless nickel-copper alloy pipe and tube. This is the specification normally quoted for hot-finished or cold-drawn seamless pipe.
ASME SB165 - the ASME equivalent of ASTM B165. The technical content is the same, and either designation may be shown on the certificate.
ASTM B725 - welded nickel-copper alloy pipe, covering pipe produced with a longitudinal weld seam, with ASME SB725 as its ASME counterpart.
ASTM B163 - seamless nickel and nickel-alloy condenser and heat-exchanger tubes, applied when the item is a small-diameter tube rather than line pipe.
ASTM B164 - nickel-copper alloy rod, bar and wire, used when the same material is required in solid section.
Dimensions for pipe are usually taken from the ASME B36.10M and B36.19M tables or from the ordering dimensions agreed in the purchase specification, and the material certificate should state both the product specification and the dimensional basis used.
Chemical Composition of UNS N04400
Alloy 400 is a single-phase nickel-copper solid solution. Copper is the only deliberate major addition, and the balance between nickel and copper is what gives the grade its combination of strength, ductility and resistance to seawater.
| Element | Requirement (weight %) |
|---|---|
| Nickel (Ni) | 63.0 minimum (typically 66–67) |
| Copper (Cu) | 28.0–34.0 |
| Iron (Fe) | 2.5 maximum |
| Manganese (Mn) | 2.0 maximum |
| Carbon (C) | 0.30 maximum |
| Silicon (Si) | 0.50 maximum |
| Sulphur (S) | 0.024 maximum |
The high nickel content keeps the structure austenitic and non-magnetic, while copper raises resistance to reducing acids and to seawater. The restricted carbon and sulphur limits are important for welded pipe, because they reduce the risk of hot cracking and intergranular attack in the weld heat-affected zone.
Mechanical Properties Required by ASTM B165
| Property | Minimum value |
|---|---|
| Tensile strength | 550 MPa |
| Yield strength, 0.2% offset | 240 MPa |
| Product condition | Annealed, as supplied |
| Structure | Austenitic, non-magnetic |
These figures describe the annealed condition that ASTM B165 covers. Seamless and welded pipe owe their useful toughness to this combination of moderate strength and high elongation, which allows cold bending, flaring and expansion without cracking. Tensile requirements are verified on each lot by the mill, and the test results are reported on the material certificate.
Dimensions, Tolerances and End Finishes
Alloy 400 pipe and tube are produced over a wide range of nominal sizes. Typical availability for seamless product includes:
Outside diameter from 6.35 mm to 254 mm
Wall thickness from 0.6 mm to 20 mm
Nominal bore from DN 15 to DN 150, expressed as millimetre nominal size
Lengths: single random, double random and cut to length
Ends: plain end, bevelled end or threaded
Forms: round tube and hydraulic tube
Wall thickness and diameter tolerances follow the product specification, and closer tolerances are normally agreed at the time of order because they affect both weight and pressure rating.
Corrosion Performance and Temperature Limits
Alloy 400 was developed for seawater service and still handles high-velocity seawater, brackish water and brine better than most copper alloys. It also resists hydrofluoric acid, neutral and alkaline salt solutions and many reducing acids, and it performs well in caustic soda environments where stress-corrosion cracking would attack other materials. Stagnant seawater in crevices and under deposits is the known weak point, so piping layouts should avoid dead legs and uncontrolled biofouling.
The nominal density is 8.80 g/cm³ and the melting range is approximately 1300–1350 °C. Continuous service in air is generally limited to about 480 °C. Above that temperature the oxide film becomes less protective, and sulphur-bearing atmospheres should be avoided at elevated temperature because nickel-rich alloys are sensitive to sulphidation.
Applications and Product Availability
Typical applications include seawater piping and desalination plant, chemical processing equipment, heat exchangers, condensers, boiler feed systems, pharmaceutical process lines, petrochemical and gas processing units, and pulp and paper mills. The grade is supplied as seamless, welded and ERW pipe, as fabricated assemblies and as matching fittings, flanges and plate, so a project can be built from a single material family with consistent corrosion behaviour.
Frequently Asked Questions
Q: What is the ASTM standard for Alloy 400 pipe?
A: Seamless pipe and tube are covered by ASTM B165, with ASME SB165 as the ASME equivalent. Welded pipe is covered by ASTM B725 with ASME SB725 as its ASME counterpart, and small-diameter heat-exchanger tube is covered by ASTM B163.
Q: What is Alloy 400 pipe made of?
A: It is a nickel-copper alloy with a minimum of 63% nickel, normally about 66–67%, balanced by 28–34% copper, with iron, manganese, carbon, silicon and sulphur held below tightly specified maximum limits.
Q: What are the minimum mechanical properties?
A: Annealed Alloy 400 pipe to ASTM B165 must reach a minimum tensile strength of 550 MPa and a minimum 0.2% offset yield strength of 240 MPa, with the ductility and toughness needed for bending and flaring.
Q: Is Alloy 400 pipe suitable for seawater?
A: Yes. It is one of the standard choices for high-velocity seawater and brine, and it resists chloride stress-corrosion cracking far better than austenitic stainless steel. Crevices, stagnant water and heavy deposits should be avoided because they promote localised attack.
Q: What is the maximum service temperature?
A: The melting range is about 1300–1350 °C, but continuous service in air is normally limited to approximately 480 °C. Sulphur-containing gases at high temperature should be avoided because they attack nickel-rich alloys.
Q: What sizes and ends are available?
A: Seamless pipe is commonly supplied from 6.35 mm to 254 mm outside diameter with 0.6 mm to 20 mm wall thickness, in nominal bores from DN 15 to DN 150, in random, double-random or cut lengths with plain, bevelled or threaded ends.
