ASTM B167 Ni-Cr-Fe Alloy Tube: A Procurement Guide to Grades, Service Envelopes, and Mill-Direct Sourcing

Most procurement decisions involving nickel alloys start with a sentence like "the client specified nickel alloy, and Inconel 600 is the cheapest of the bunch, so let's go with that." Sometimes that is the right call. Most of the time it is a quiet mistake: a grade picked for name recognition, not for the service it will actually see. ASTM B167 covers the Ni-Cr-Fe family that includes Inconel 600, 601, 617, 690, and 693, plus four additional UNS designations, and each one has a different operating envelope for temperature, atmosphere, and chloride exposure. Specifying them as interchangeable is how plants end up with 600 cracking in caustic service, or 690 being over-specified and over-budgeted for a duty that 600 would have handled cleanly.

This guide is the framework we use at EZ Steel Industrial when an EPC engineer or a chemical-plant maintenance lead sends us a b167 ni-cr-fe alloy tube RFQ. It organizes the family by service, not by UNS number, and it lines up the chemistry, mechanical properties, and the procurement checkpoints that actually drive field performance.

1. What ASTM B167 Actually Covers

ASTM B167 / B167M is the specification for nickel-chromium-iron alloy seamless pipe and tube. ASME SB-167 is the pressure-vessel code version of the same specification. B167 covers the following UNS designations, all solid-solution strengthened:

• UNS N06600 (Inconel 600): the baseline Ni-Cr-Fe alloy, 72% Ni min, 14–17% Cr, 6–10% Fe. General-purpose high-temperature and corrosion service. The default "nickel alloy" for furnace components, heat-treating baskets, and caustic evaporators.
• UNS N06601 (Inconel 601): N06600 with 1.0–1.7% Al added, which gives a much more stable oxide film. The right call for cyclic high-temperature service up to 1,200 °C where N06600 would scale and spall.
• UNS N06025 (Inconel 602CA): higher carbon (0.15–0.25%), higher Cr (24–26%), with Ti and Zr microalloying. The strongest and most oxidation-resistant grade in the family; aimed at severe radiant-tube and reformer service.
• UNS N06617 (Inconel 617): adds Co and Mo, which raises high-temperature strength significantly. The go-to grade for advanced ultra-supercritical power and high-temperature gas-cooled reactor components.
• UNS N06690 (Inconel 690): roughly 30% Cr, lower Fe. The chloride-stress-corrosion-cracking grade; standard for nuclear steam-generator tubing and for nitric acid / hydrofluoric acid duty.
• UNS N06693 (Inconel 693): even higher Cr, with Al and Nb microalloying. Optimized for aggressive oxidizing atmospheres; specialty grade.
• UNS N06603, N06045, N06674, N06696: specialty entries covering specific composition variants. N06674 in particular is a Ni-Fe-Cr-W alloy for high-temperature service where the tungsten addition improves creep strength.

All B167 grades are typically supplied in the annealed condition (most common delivery state), in hot-worked or cold-worked forms for heavier-wall tube, and in seamless form by default. Welded B167 tube is uncommon — the standard is seamless — and buyers who need welded nickel tube usually go to ASTM B619 instead.

2. The Five Procurement Questions That Drive Grade Selection

B167 grade selection is much easier if you answer these five questions before opening the catalog. None of them are exotic — they are the same questions the mill will ask back if you call with an RFQ.

1. What is the maximum continuous operating temperature? 600 °C and 1,100 °C are not the same alloy. 600 °C continuous is N06600 territory; 1,100 °C continuous needs N06025 or N06601 with Al.
2. Is the atmosphere oxidizing, reducing, or cyclic? Cyclic service kills the wrong grade by spalling the protective oxide. N06601 with Al is the right call for cyclic duty; N06600 is for steady-state oxidizing.
3. What is the chloride or caustic exposure? Chloride-bearing service in hot water rules out most austenitic stainless and points to N06690. Caustic service above 50% concentration also points to nickel-iron-chromium alloys.
4. Is creep strength critical? For service above 700 °C with significant sustained load, N06617 or N06674 is the right call. N06600 is not a creep-resistant grade by design.
5. Is the component nuclear, aerospace, or chemical? The certification, traceability, and NDT requirements differ sharply. Nuclear steam-generator tubing is N06690 with very specific MTC scope; aerospace applications may need additional independent witnessing.

Most of the wrong-grade purchases we see come from skipping questions 3 and 4. A plant buys 600 for hot chloride water because the spec said "nickel alloy," and the tubes fail in eighteen months. A power plant buys 690 for a 600 °C furnace because the consultant wanted "premium," and they spent three times the budget for a grade they did not need.

3. Service-to-Grade Quick Map

The table below maps the most common B167 service cases to a recommended grade. It is a starting point — not a substitute for an engineering review on critical service — but it covers the bulk of industrial RFQs we see at power plant & aerospace, chemical, and petrochemical duty.

4. Chemistry and Mechanical Property Snapshot

B167 is a mechanical-property-as-a-function-of-condition specification. The values change with delivery condition (hot-worked, cold-worked, annealed) and with size (≤127 mm vs >127 mm OD). The table below summarizes the room-temperature minimum mechanical properties for the most commonly ordered grades. The full table runs to ten UNS designations and is worth keeping on hand for any B167 RFQ.

5. Fabrication: Welding, Bending, and Heat Treatment

B167 grades are fabricated by the usual nickel-alloy methods, but they are not as forgiving as austenitic stainless. Three things matter.

Welding filler selection. For N06600, the standard filler is ERNiCr-3 (Inconel 82) or ENiCrFe-3. For N06601, ERNiCrFe-12 or ERNiCrCoMo-1 is preferred because the Al content in the base metal needs a matching filler. For N06617, ERNiCrCoMo-1 is the standard. For N06690, ERNiCr-3 works but the high-Cr weld metal benefits from ERNiCrFe-7 for matching corrosion performance. The wrong filler metal is a top-three cause of weldment failure in B167 components.

Post-weld heat treatment. Most B167 grades are used in the as-welded annealed condition, and PWHT is not always required. The exception is thick-wall high-pressure service in N06600 or N06617, where a stress-relief at 870–980 °C is sometimes specified to relax residual welding stress. Always check the design code — ASME Section I, Section VIII, or B31.1 / B31.3 — rather than guess.

Bending. Nickel alloys work-harden faster than austenitic stainless. Minimum bend radius is 1.5× to 3× OD for annealed material, depending on grade. N06600 in the cold-worked condition can be bent at 1.5× OD, but N06617 in the annealed condition needs 3× OD. For U-bend heat-exchanger service, the same post-bend solution-anneal rules apply as for stainless — typically 1,040–1,080 °C for 15–30 minutes in a controlled atmosphere, then rapid cool. Bending without the subsequent anneal sensitizes the grain boundary and opens the door to chloride SCC.

6. Standards and Test Certificate Scope

A B167 RFQ should always specify the MTC type and the NDT scope. Both have direct cost impact and direct traceability impact.

• MTC type: EN 10204 3.1 (mill-issued, with traceable heat number) is the default. EN 10204 3.2 (mill-issued, independently witnessed by an inspection agency) is required for nuclear, pressure-boundary, and any order going into an ASME-stamped exchanger.
• Chemistry verification: ASTM B880 covers the chemical analysis method for nickel alloys. Always request the B880 test report, not just a nominal chemistry statement.
• Hydrostatic test: B167 calls for hydrostatic test on every tube, or a substitute non-destructive electric test (eddy current or ultrasonic) when agreed. Specify which one you want — the test method affects both cost and traceability.
• Dimensional tolerance: standard B167 tolerances are tighter than for carbon or stainless. For nuclear steam-generator tubing, tighter-than-standard tolerances (often called out as "nuclear-grade dimensional") are routinely specified.
• Surface finish: pickled, bright-annealed, or mill finish. Bright-annealed in a controlled hydrogen atmosphere is the right call for nuclear and aerospace service.

7. The Six Procurement Checkpoints for B167 RFQs

Add these six checkpoints to every B167 RFQ. They are the same list we run our own internal reviews against, and they prevent most of the after-sales disputes that nickel-alloy orders tend to generate.

1. UNS designation named in full. not just "Inconel 600" — write "UNS N06600 per ASTM B167 / B167M, latest edition." Trade names are not standards.
2. Delivery state and condition. annealed, hot-worked annealed, or cold-worked annealed; size range (≤127 mm or >127 mm OD); heat-treatment record if any.
3. MTC type and edition. EN 10204 3.1 vs 3.2; ASTM B880 chemistry report; ASME SB-167 if the order is going into a code-stamped vessel.
4. NDT scope. hydrostatic test on every tube, or substitute eddy current / ultrasonic; specification of acceptance criteria; PMI (positive material identification) on a sample basis.
5. Surface finish, packaging, and traceability. pickled / bright-annealed / mill; end caps; desiccant for sea freight; per-tube marking with heat number.
6. Documentation bundle format. one PDF per shipment with MTC, dimensional report, NDT report, PMI report, visual inspection record. Anything less is hard to file into a quality system.

8. Bundled Sourcing: Where B167 Sits in a Full Pipe Package

B167 tube rarely arrives alone. A typical package also needs a matching pipe fittings set, a pipe flange set, and a gasket and stud-bolt kit. The same plant often has a b407 incoloy 800 tube section for the lower-temperature part of the loop, a b165 monel 400 tube section for hydrofluoric acid, and an ASTM B163 nickel-alloy tube section for the reboiler. Sourcing all of these from a single mill means one MTC format, one heat-number traceability system, one shipping window, and one set of customs paperwork at the receiving port.

EZ Steel Industrial's three-location network is set up for exactly this. Our Lishui base runs the stainless and copper-nickel family, our Yangzhou base covers the carbon and alloy range, and our Cangzhou location handles alloy-steel inventory and custom fittings. A B167 RFQ that comes in alongside B407, B165, B163, and the matching flange and gasket package can be issued as one order, manufactured in parallel, MTC'd together, and shipped as one consignment. For EPC contractors working against a tight construction schedule, that single-window model usually beats the lowest unit price from three separate vendors.

9. Six Mistakes That Still Show Up on B167 RFQs

A short list of mistakes our engineering desk has caught in the last twelve months. None of them are exotic; all of them are preventable.

• Specifying N06600 for high-chloride hot water. N06600 will eventually crack by chloride stress corrosion in hot chloride-bearing water. N06690 is the standard nuclear and chlor-alkali grade for that reason.
• Specifying N06690 for general furnace service. N06690 is over-engineered and overpriced for most furnace muffle duty. N06600 is the right call and saves 30–50% of the alloy surcharge.
• Skipping the post-bend anneal on N06600 U-bends. The cold-worked bend is sensitized and will crack under caustic or chloride exposure. The anneal is not optional.
• Welding N06601 with ERNiCr-3. The aluminum content in the base metal does not transfer to the weld pool with the standard 600 filler. Use a matching filler (ERNiCrFe-12 or ERNiCrCoMo-1) or the weld zone will be the weak link.
• Treating "Inconel" as a single material. 600, 601, 617, 690, and 693 are different alloys with different chemistry, different temperature ceilings, and different cost. Always name the UNS number in the RFQ.
• Accepting a generic MTC without per-tube traceability. A B167 MTC should be per-heat and per-tube-batch, with the heat number on each tube. Without that, field repair and quality investigation become guesswork.

10. Putting It Together for Your Next B167 RFQ

Before you send the next B167 inquiry, run it through this seven-line internal check:

1. Service case and atmosphere identified, including cyclic vs steady state
2. Operating temperature window and pressure stated
3. UNS designation named in full (e.g., UNS N06600, N06601, N06617, N06690)
4. Delivery state and condition specified (annealed, hot-worked, cold-worked)
5. Geometry locked: OD, wall, length or bend radius
6. MTC type, NDT scope, and PMI requirement specified
7. Surface finish, packaging, and bundled-supply scope agreed

A request that has all seven lines will get a quote you can compare apples to apples against other mills. A request missing three or more of them will get three different quotes — and you will end up comparing paper rather than metallurgy.

If you are at the early scoping stage, our engineering team is happy to review a one-page duty summary (fluid, atmosphere, maximum temperature, expected pressure, and any dimensional constraints) and come back with a recommended grade, a delivery state, and a budget indication. For tighter scopes, the same team can move directly into a formal RFQ response with full MTC, dimensional, NDT, and PMI documentation.