What ASTM B165 Covers
ASTM B165 is the specification for cold-finished seamless pipe and tube made from the nickel-copper alloy UNS N04400. ASME SB165 is technically identical and extends the material into ASME construction. The alloy is a solid-solution nickel-copper grade that can be strengthened by cold work and retains useful toughness from cryogenic temperatures up to roughly 480 C.
Product is supplied as seamless, welded, electric-resistance-welded or fabricated pipe and tube. Cold finishing delivers tight dimensional control and a smooth bore, which is why the cold-finished seamless form dominates instrument lines, heat exchangers and small-bore chemical service.
| Standard | ASTM B163 / SB163, B165 / SB165, B725, B730 |
|---|---|
| Alloy | UNS N04400 |
| Product type | Seamless pipe and tube, welded pipe and tube |
| Tube form | Straight tubes and U-bend tubes |
| Outside diameter | 6 to 610 mm |
| Wall thickness | 0.8 to 30 mm |
Chemical Composition of UNS N04400 Cold Finished Seamless Pipe
| Element | Nickel | Copper | Iron | Manganese | Carbon | Silicon | Sulfur |
|---|---|---|---|---|---|---|---|
| Requirement, % | 63.0 min | 28.0 to 34.0 | 2.50 max | 2.00 max | 0.30 max | 0.50 max | 0.024 max |
The high nickel content provides the matrix and the resistance to chloride-bearing water, while copper additions give the alloy its useful performance in reducing acids such as sulfuric and hydrofluoric acid. Neither element is a precipitation hardener, so strength is obtained by cold reduction rather than by heat treatment.
Mechanical Properties by Condition
The specification tabulates three condition classes, identified as A, B and C. The required condition is stated on the purchase order, and it determines both the strength level and the minimum elongation that the finished pipe must meet.
| Condition | Tensile strength, min, ksi [MPa] | Yield strength, min, ksi [MPa] | Elongation, min % |
|---|---|---|---|
| A | 70 [480] | 28 [195] | 35 |
| B | 70 [480] | 25 [170] | 35 |
| C | 85 [585] | 55 [380] | 15 |
Condition C represents the cold-worked high-strength class. It trades ductility for strength and is normally selected where wear, pressure loading or mechanical abuse dominates the duty.
Corrosion Behaviour and Service Limits
The alloy resists a wide range of marine and chemical environments, from pure water through to non-oxidizing mineral acids, salts and alkalis. Two rules of thumb govern its use:
In reducing media it outperforms pure nickel, and in oxidizing media it outperforms pure copper, but its overall performance is better in reducing than in oxidizing conditions.
It performs well in sulfuric and hydrofluoric acid service; however, aeration raises the corrosion rate noticeably. It can handle hydrochloric acid, but dissolved oxidizing salts accelerate attack sharply.
It resists neutral, alkaline and acidic salts, while resistance to oxidizing salts such as ferric chloride is comparatively poor.
Its resistance to chloride ion stress corrosion cracking is excellent, a key reason for its popularity in seawater systems.
Mechanical properties are retained from sub-zero service up to approximately 480 C. Above that range, strength loss and oxidation become the limiting factors for the specific duty.
Applications and Manufacturing Standards
Typical uses of B165 cold-finished seamless pipe include marine fixtures, fasteners and brackish or seawater equipment; chemical processing pipework, vessels and components handling acid and alkaline solutions; and general equipment such as valves, pumps, springs, heat exchangers, and gasoline or freshwater storage tanks.
ASTM B165: cold-finished seamless pipe and tube of nickel-copper alloy UNS N04400.
ASME SB165: identical technical content, adopted for ASME construction.
ASTM B163 and ASME SB163: seamless tube for heat exchanger and condenser service.
ASTM B725: welded pipe and tube of the same alloy family.
Frequently Asked Questions
Q: What is UNS N04400?
It is a nickel-copper alloy containing about 63 percent nickel and 28 to 34 percent copper, strengthened by cold work rather than by heat treatment.
Q: Which standards apply to the seamless form?
ASTM B165 and ASME SB165 cover the cold-finished seamless pipe and tube, while ASTM B163 and ASME SB163 cover seamless tube for heat exchanger and condenser service.
Q: What is the maximum service temperature?
Mechanical properties hold from sub-zero conditions to about 480 C. Above that level the specific duty must be assessed for strength loss and oxidation.
Q: Is the alloy prone to chloride stress corrosion cracking?
No. Its excellent resistance to chloride ion stress corrosion cracking is one of the main reasons it is chosen for seawater and chloride-bearing chemical service.
Q: Where does aeration cause a problem?
In sulfuric and hydrofluoric acid service, aeration increases the corrosion rate, and in hydrochloric acid service dissolved oxidizing salts greatly accelerate attack.
Q: Does cold finishing affect corrosion performance?
Cold reduction raises strength but also leaves residual stress. Where high strength and maximum corrosion resistance are both required, the stress-relieved condition should be evaluated for the duty.
