ASTM B163 Tubing in UNS N06601
ASTM B163 covers seamless nickel and nickel alloy tubing, and UNS N06601 is the nickel-chromium-aluminium grade supplied against it. The aluminium addition is what separates this grade from plain nickel-chromium alloys: it lets the surface form a tightly adherent aluminium oxide layer that keeps protecting the metal where a simple chromia scale would spall. The pickled and annealed condition means the tube has been annealed to restore ductility and then pickled to remove the oxide scale left by hot working and heat treatment, leaving a clean, uniform surface that is easier to inspect, weld and bend.
Wall thickness, outside diameter and length are controlled by the specification, and the annealed and pickled finish is the normal supply condition for tubing that will be fabricated into furnace assemblies and process internals.
Why the Aluminium Addition Matters
UNS N06600 depends on chromium alone for oxidation resistance. Adding aluminium in UNS N06601 produces a protective oxide that stays in place through thermal cycling, which is why the grade is chosen for retorts, muffle furnaces, radiant tubes, roller hearth furnace parts and supports, and for petrochemical internals that repeatedly heat and cool.
The trade off is mechanical. UNS N06601 is generally lower in tensile strength than UNS N06600, but it offers better high temperature oxidation resistance. Choosing between the two is therefore a question of service environment rather than of one grade being universally superior.
Comparing UNS N06600 and UNS N06601
| Property | UNS N06600 | UNS N06601 |
|---|---|---|
| Density | 8.47 g/cm3 | comparable to the nickel-chromium family |
| Melting range | 1413 degC, 2580 degF | aluminium bearing, high temperature grade |
| Tensile strength | 655 MPa, 95000 psi | lower than UNS N06600 |
| Yield strength, 0.2 % offset | 310 MPa, 45000 psi | lower than UNS N06600 |
| Elongation | 40 % | ductile, annealed and pickled supply |
| Oxidation resistance | good, chromium oxide scale | superior, aluminium oxide scale |
The density, melting range and mechanical values given above are those of UNS N06600 and are listed here for comparison; they are frequently published in the wrong column when the two grades are tabulated together, so the basis of each figure should always be checked against the relevant specification before a design is frozen.
| Element | Requirement, % |
|---|---|
| Nickel | 72.00 min |
| Chromium | 14.00-17.00 |
| Iron | 6.00-10.00 |
| Carbon | 0.15 max |
| Manganese | 1.00 max |
| Silicon | 0.50 max |
| Sulfur | 0.015 max |
| Copper | 0.50 max |
This table is the chemical composition of UNS N06600 seamless tube, shown as the comparison baseline; the aluminium bearing UNS N06601 grade carries the higher nickel-chromium base with an aluminium addition instead of the plain chromium-only balance.
Supply Range and Specifications
| Item | Range |
|---|---|
| Specifications | ASTM B163, B167, B751, B775, B829 |
| Tube type | seamless tube, welded pipe |
| Alloy | UNS N06601 |
| Manufacturing | cold worked, hot worked |
| Outside diameter | 6-1016 mm |
| Wall thickness | 0.8-50 mm |
| Schedules | SCH5, SCH10, SCH10S, SCH20, SCH30, SCH40, SCH40S, STD, SCH60, SCH80, SCH80S, XS, SCH120, SCH140, SCH160 |
| Finish | polished, annealed and pickled, bright annealed |
| Ends | plain end, bevelled end, threaded, screwed |
Typical Service Applications
Heat treatment equipment: industrial furnaces, retorts, muffle furnaces, baskets and fixtures.
Ceramics and petrochemical plants: roller hearth furnaces and process equipment.
Power and chemical plants: heat exchangers, turbines and components exposed to heat and corrosive media.
Aerospace and marine: parts needing high temperature strength.
Frequently Asked Questions
Q: What is UNS N06601?
It is a nickel-chromium-aluminium alloy supplied as seamless tube under ASTM B163 and as pipe under the related ASTM specifications.
Q: What does pickled and annealed mean?
The tube is annealed to restore ductility after cold working and then pickled in acid to remove oxide scale, giving a clean, uniform surface.
Q: How does it differ from UNS N06600?
UNS N06600 offers higher tensile strength, while UNS N06601 with its aluminium addition gives better high temperature oxidation resistance.
Q: Which industries use this tube?
Heat treatment, ceramics, petrochemical, power generation, chemical processing, aerospace and marine engineering.
Q: Is the tubing seamless?
ASTM B163 covers seamless tubing, which is why the pickled and annealed seamless condition is the usual choice for furnace and process duty.
Q: Which finishes and end preparations are available?
Polished, annealed and pickled, or bright annealed finishes, with plain, bevelled, threaded or screwed ends.
