ASTM B725
ASTM B725 Nickel Alloy Seamless & Welded Tubes
ASTM B725 is the standard specification for Nickel-Copper Alloy (UNS N04400) seamless and welded tubing for general service, marine, and chemical applications. This standard is primarily used in engineering and industrial applications where high corrosion resistance and strength are required, especially in sea water environments.
Key Features
Corrosion Resistance – Outstanding resistance to seawater and corrosive solutions.
High Strength – Suitable for moderate to high-pressure applications.
Excellent Fabricability – Can be formed, welded, and machined easily.
Versatility – Applicable for piping, tubing, condensers, and heat exchangers.
Dimensional Accuracy – Strict tolerances ensure compatibility with industrial systems.
ASTM B725 Technical Specification
| Specification Aspect | Details |
|---|---|
| Standard | ASTM B725 |
| Material Type | Nickel-Copper Alloy (Cu-Ni, typically 70/30) |
| Product Forms | Seamless & Welded Tubes |
| Outer Diameter (OD) | 0.25 in – 12 in (6.35 mm – 300 mm) |
| Wall Thickness | 0.035 in – 0.5 in (0.9 mm – 12.7 mm) |
| Length | Up to 20 ft (6 m) standard; can be customized |
| Finish | Annealed, pickled, or as specified |
| Tolerances | ASTM B575, ASTM B160 |
| Surface Quality | Smooth, free of defects, burrs, and scaling |
Chemical Composition
| Element | UNS N04400 (Cu-Ni 70/30) Typical % |
|---|---|
| Copper (Cu) | 68.0 – 71.0 |
| Nickel (Ni) | 29.0 – 31.0 |
| Iron (Fe) | 0.5 – 2.0 |
| Manganese (Mn) | 0.5 max |
| Carbon (C) | 0.10 max |
| Sulfur (S) | 0.03 max |
| Phosphorus (P) | 0.03 max |
Mechanical Properties
| Property | Value (Typical) |
|---|---|
| Tensile Strength (UTS) | 45,000 – 55,000 psi (310 – 380 MPa) |
| Yield Strength (YS) | 20,000 – 35,000 psi (140 – 240 MPa) |
| Elongation (%) | 30 – 50 |
| Hardness (Brinell) | 80 – 130 |
Physical Properties
| Property | Value (Typical) |
|---|---|
| Density | 8.94 g/cm³ |
| Melting Point | 1240 – 1350 °C |
| Thermal Conductivity | 29 W/m·K |
| Electrical Resistivity | 0.45 μΩ·m |
| Coefficient of Thermal Expansion | 16.5 × 10⁻⁶ /°C |
Type of Products
Seamless tubes – produced by extrusion or rotary piercing.
Welded tubes – made from rolled and welded plates.
Custom-fabricated tubes – bent or machined for special applications.
ASTM B725 Grades
- UNS N02200
- UNS N02201
- UNS N04400
Processing & Manufacturing
Melting & Casting – High-quality nickel and copper are melted and cast into billets.
Hot Extrusion / Piercing – Billets are extruded or pierced to produce seamless tubes.
Rolling & Welding – For welded tubes, plates are rolled and welded using controlled processes.
Heat Treatment – Annealing improves ductility and corrosion resistance.
Finishing – Tubes are pickled, straightened, and tested for dimensional accuracy.
Inspection & Testing – Includes chemical analysis, mechanical testing, and nondestructive testing (NDT).
Applications
Marine Engineering – Piping, condensers, and heat exchangers in ships and offshore platforms.
Desalination Plants – Corrosion-resistant tubes for evaporators and condensers.
Chemical Industry – Handling corrosive fluids and chemicals.
Power Plants – Cooling systems and condensers exposed to seawater.
Oil & Gas – Pipes and tubes in saltwater environments and chemical processing.