ASTM B167 Ni-Cr-Fe Alloy Tube Buyer's Guide: UNS N06600, N06690 & N06693 Seamless Pipe for High-Temperature Service

EZ Steel Industrial · B2B Buyer's Guide

A mill-direct sourcing playbook for procurement, EPC and project engineers who need to specify nickel-chromium-iron alloy tubes for power, petrochemical, aerospace and nuclear service.

If you have ever had a process line shut down because a heat-exchanger tube failed prematurely, you already know why the right specification matters more than the lowest price. ASTM B167 is the specification that defines the chemistry, mechanical properties, dimensions and testing requirements for seamless b167 ni-cr-fe alloy tube — the workhorse family of nickel-chromium-iron solid-solution alloys that includes UNS N06600 (Inconel 600), UNS N06690, UNS N06693 and N06601. They sit in the sweet spot where austenitic stainless steels run out of high-temperature strength and where exotic nickel-base superalloys become uneconomical.

This guide is written for the buyer who has to put a mill-direct order on paper — not for the metallurgist writing a thesis. It walks through what ASTM B167 actually requires, where each UNS grade fits, how it cross-references to ASME SB167, EN and GB/T standards, what testing and documentation to demand, and how to size a project with heat exchanger tube fabricators, pipe fittings and power plants & aerospace end-users in mind. Throughout, examples are drawn from the catalog and mill capabilities of EZ Steel Industrial, a Cangzhou–Yangzhou–Lishui based manufacturer with ISO 9001, API 5L and API 5CT credentials, which has been rolling nickel and copper-nickel tubes for power, refinery and marine projects since 1994.

1. What ASTM B167 Actually Covers

ASTM B167 / B167M is titled "Standard Specification for Nickel-Chromium-Iron Alloys (UNS N06600, N06601, N06617, N06625, N06690, N06693, N06025, N06045, N06230, N06696, N08120, N08320, N08700, and N08925) Seamless Pipe and Tube." In plain terms it covers:

Form: Seamless, cold-worked or hot-worked, annealed or solution-annealed.
Size range: Typically outside diameters from ~5 mm (for heat-exchanger tube) up to ~610 mm (for large pipe), with wall thickness from 0.5 mm to 60 mm depending on diameter and schedule.
Grades: The UNS list above, each with its own chemistry and mechanical envelope.
Testing: Chemical analysis, tensile test, hardness, grain size (where required), hydrostatic or nondestructive electric test, flattening test, and a corrosion test on certain grades.
Documentation: Manufacturer's test report per EN 10204 3.1 (or 3.2 when notarised) with heat number traceability.

ASME SB167 is the ASME Boiler and Pressure Vessel Code version — chemistry and mechanical properties are identical, but the SB designation is mandatory for Section I (power boilers), Section III (nuclear) and Section VIII (pressure vessels) construction. If your project is going to be ASME-stamped, you must order SB167, not just B167. The b167 ni-cr-fe alloy tube stocked and produced by EZ Steel Industrial can be dual-certified to ASTM/ASME on request, which is a frequent ask for nuclear and refinery retubing orders.

2. The Four Grades Buyers Actually Specify

Although ASTM B167 covers 14 UNS numbers, in commercial practice about 95% of inquiries cluster around the four grades below. Choosing among them comes down to the maximum service temperature, the presence of chlorides, the need for nitriding resistance, and whether the tube will be welded.

2.1 UNS N06600 (Alloy 600 / Inconel 600)

The original workhorse. Nickel ≥72%, chromium 14–17%, iron 6–10%, carbon ≤0.15%. Excellent resistance to chloride-ion stress corrosion cracking, good resistance to dry chlorine and hydrogen chloride gas, satisfactory strength to about 1093 °C. Used in steam generator tubes, heat-treat furnace muffles, caustic evaporators and ethylene dichloride crackers. Most widely quoted b167 ni-cr-fe alloy tube grade in B2B inquiries.

2.2 UNS N06601 (Alloy 601 / Inconel 601)

Adds ~1.0–1.7% aluminum for outstanding oxidation resistance to 1200 °C, especially under cyclic conditions. Preferred for catalyst support grids in ethylene furnaces, combustion chambers, and aerospace exhaust components. Often used in power plants & aerospace auxiliary systems where the metal skin sees 1000 °C+.

2.3 UNS N06690 (Alloy 690 / Inconel 690)

Chromium raised to 27–31% — the high-Cr variant designed specifically to resist stress corrosion cracking in caustic, nitric acid, and high-purity water. The default selection for new-build nuclear steam generator U-tubes (replacing Alloy 600 in most PWR fleets), and increasingly used in spent fuel storage and reprocessing.

2.4 UNS N06693 (Alloy 693)

Chromium 27–31% plus 2.5–4.0% aluminum and 1.0–2.5% niobium. A relatively recent addition optimised for metal dusting resistance in syngas and ammonia plants, and for high-temperature sulfidation in coal-fired boiler environments. Specified when the process gas is reducing and carbon-active.

Spec tip: When your datasheet just says "Inconel 600 tube", confirm with the mill that you are getting UNS N06600 to ASTM B167 — and not a cheaper look-alike such as a 304H or a 1.4529. Only B167 carries the ≥72% Ni floor that gives the alloy its stress-corrosion-cracking immunity.

3. Chemistry and Mechanical Properties at a Glance

The two tables below summarise the limits that buyers see most often on an MTR. Use them when comparing supplier quotations — if a quote does not meet these numbers, it is not ASTM B167 material, regardless of the label.

3.1 Chemical composition (wt %, max unless range given)

Element	N06600	N06601	N06690	N06693
Ni (min)	72.0	58.0–63.0	58.0 min	balance
Cr	14.0–17.0	21.0–25.0	27.0–31.0	27.0–31.0
Fe	6.0–10.0	remainder	7.0–11.0	2.5–6.0
C	0.15	0.10	0.05	0.15
Mn	1.00	1.00	0.50	1.00
Si	0.50	0.50	0.50	0.50
Cu	0.50	1.00	0.50	0.50
Al	—	1.0–1.7	—	2.5–4.0
Ti	—	—	—	1.0
Nb+Ta	—	—	—	1.0–2.5
S	0.015	0.015	0.015	0.01

3.2 Mechanical properties at room temperature (annealed condition)

Property	N06600 (≤127 mm)	N06600 (>127 mm)	N06601 (cold-worked ann.)	N06690 (ann.)	N06693 (ann.)
Tensile strength, min MPa	550	515	550	586	586
Yield (0.2%), min MPa	205	170	240	241	241
Elongation in 50 mm, min %	35	35	30	30	30
Hardness, max HRB	95	95	100	100	100

For high-temperature service, ask the mill for the 1000-hour creep-rupture data at your design temperature — these curves are the actual basis for the allowable stress values used in ASME Section II Part D. EZ Steel Industrial publishes the room-temperature and elevated-temperature data for each heat as part of its MTR package.

4. Where B167 Tubes Are Used in Real Projects

Power generation: Superheater and reheater tubes in coal-fired boilers running at 620–700 °C, where chloride-bearing flue gas would attack stainless steel. Power plants & aerospace turbines also use N06601 for transition pieces and exhaust ducts.
Petrochemical and refinery: Ethylene cracking furnace tubes, reformer outlet pigtails, and ammonia converter internals. Often paired with pipe fittings in matching ASME B16.9 BW elbows and equal tees for the field fabrication.
Nuclear: Pressurised water reactor steam generator U-tubes in N06690 (the global standard since the 1990s replacement campaign for N06600). Specified to ASME SB167 with Charpy impact, grain size and corrosion test data per RCC-M Section II when required.
Heat treatment furnaces: Radiant tubes, muffles, retorts, and walking-beam components in N06601 or N06693. Common in continuous annealing lines and aluminium homogenising furnaces.
Chemical processing: Caustic evaporators, chlorine cells, nitric acid coolers, vinyl chloride monomer (VCM) production — every place where chlorides and high temperature meet.
Marine and offshore: Seawater-tolerant heat-exchanger shells and lube-oil coolers, often delivered alongside copper-nickel heat exchanger tube bundles for the lower-temperature half of the system.

5. Cross-Reference to Other Standards

Few B2B projects accept a single standard. A refinery in Saudi Arabia may demand ASME SB167 with ASTM B167 chemistry and an EN 10204 3.2 MTR; a Chinese EPC contractor may ask for the GB/T equivalent (GB/T 15008 or GB/T 2882 depending on the grade); a European pressure-vessel shop may insist on the EN 10216-5 or EN 10028-7 number on the certificate even when the metal itself is identical. The table below shows the most common cross-references the EZ Steel Industrial technical team is asked about.

UNS grade	ASME	EN / DIN	GB/T	Common trade name
N06600	SB167	2.4816 / NiCr15Fe	NS3102 / GH600	Inconel 600, NCF 600
N06601	SB167	2.4851 / NiCr23Fe	NS3103 / GH601	Inconel 601, NCF 601
N06690	SB167	2.4642 / NiCr29Fe	NS3105 / GH690	Inconel 690, NCF 690
N06693	SB167	— / NiCr29FeAlNb	— / GH693	Inconel 693
N06625	SB444 / SB167	2.4856 / NiCr22Mo9Nb	NS3306 / GH625	Inconel 625

In practice the chemistry envelopes are nearly identical. The big differences are the optional supplementary tests (impact at -196 °C, intergranular corrosion per ASTM G28, grain size per ASTM E112) that some end-users add to their procurement specification. Decide those requirements up front, because adding a low-temperature impact test after the heat has been poured typically costs you 10–14 calendar days of cycle time.

6. Sizes, Schedules and Tolerances

Most B167 inquiries fall into one of three size buckets, each with its own tolerance regime and lead time.

Heat-exchanger tube (small OD): OD 6–76 mm, wall 0.5–6 mm, in straight lengths up to ~24 m or U-bent. Hard tolerance on OD and wall (typically ±0.10 mm on OD, ±10% on wall). Supplied in solution-annealed, pickled, and 100% hydrostatically tested bundles. Often cross-quoted against heat exchanger tube in ASTM A213 or ASME SB163 for non-nickel grades.
Process pipe (medium OD): NPS ½" to 16" (OD 21–406 mm), schedules 5S through XXS, random length 4–7 m. Hard tolerance on OD per ASME B36.19. Most refinery and ethylene plant orders land here.
Large structural and header pipe: OD up to ~610 mm, heavy wall up to 60 mm, fixed or double-random length. Used for boiler headers, reheater inlet lines, and aerospace ground-support equipment. EZ Steel Industrial's Yangzhou mill is set up for this range.

A practical tip: specify the actual operating OD and wall rather than just a schedule number when the line has been hydraulically optimised. Schedule 40S in 2" nominal is 60.3 × 3.91 mm in stainless, but a B167 nickel pipe in the same NPS will quote to 60.3 × 3.91 mm as well — the supplier will assume the stainless dimensions unless you say otherwise.

7. Testing and Documentation Buyers Should Require

A complete B167 MTR package is not the paper that comes "free" with the tube — it is a deliverable you should put on the purchase order as its own line item. At a minimum, ask for:

Mill test certificate (MTC) per EN 10204 3.1 — chemistry, mechanical properties, hardness, grain size, heat treatment batch, hydrostatic or NDT result. For nuclear and high-pressure boiler service, upgrade to 3.2 (notarised by an independent inspector such as SGS, BV, TÜV or DNV).
Hydrostatic test per ASTM B167 §12, typically at the mill test pressure calculated from the Barlow formula. If the tube is intended for an ASME Section VIII vessel, the test pressure may be higher than the standard formula and must be stated on the PO.
Nondestructive testing: ultrasonic (per ASTM A388 or E213) and/or eddy current (per ASTM E309) on each tube for defect detection. Radiographic test is sometimes called out for thick-wall pipe.
Positive material identification (PMI) using X-ray fluorescence on every tube. EZ Steel Industrial runs 100% PMI on the mill exit conveyor and keeps the spectrum in the digital MTR file.
Surface finish — pickling, bright annealing, or as-drawn. Pickled is the most common for petrochemical use; bright annealed is preferred when the tube is going into a high-purity or food/pharma process.
Dimensional report with actual OD, wall, and ovality for each tube (or statistical sample if the order is large).

Save 10–14 days of cycle time by attaching the above list to your RFQ. Every additional requirement added after the order is placed typically triggers a re-confirmation cycle at the mill.

8. Why B167 Tube Is Often Bundled with Fittings, Flanges and U-Bends

A heat-exchanger retubing job is rarely a tube-only order. The same project usually needs:

Matching pipe fittings in B16.9 (butt-weld elbows, equal tees, reducers, caps) in the same UNS grade or a compatible weldable grade. EZ Steel Industrial manufactures pipe fittings in carbon, stainless and nickel alloy from the Cangzhou facility.
Flanges in ASME B16.5 / B16.47 — typically forged, slip-on or weld-neck, RTJ or RF face, in a matching or weldable grade.
U-bent tubes for floating-head exchangers. Bending radius is typically 1.5× to 3× the OD; post-bend stress relief or solution anneal may be required by the exchanger fabricator.
Finned tubes for the air-side or the gas-side of the exchanger when the heat-transfer coefficient on the shell side is low. Aluminium or copper fins are most common; integral finned (extruded or embedded) is used for higher temperatures.

Bundling the tube with the fittings and flanges from a single supplier has three real advantages: (1) one MTR file covering the whole assembly, (2) no chemistry mismatch on welding, and (3) a single shipment so you can do receiving inspection in one go rather than four. EZ Steel Industrial ships integrated packages for ethylene, refinery and nuclear retubing projects under this model.

9. A Buyer's Checklist for the RFQ

Use this list to draft a tight inquiry. The more boxes you can fill in, the closer the quotation will be to a firm price.

Standard: ASTM B167 / ASME SB167 / dual? Other standards on the MTR (EN 10204 3.1 / 3.2, GB/T, EN 10028-7)?
UNS grade: N06600 / N06601 / N06690 / N06693 / N06625? Or "Inconel-equivalent"?
Form: seamless tube, seamless pipe, U-bent tube?
OD × wall × length, in mm — not nominal pipe size.
Quantity: pieces or kilograms? Total meters or feet?
Heat treatment: solution annealed, stress relieved, bright annealed?
Surface finish: pickled, bright annealed, as-drawn?
Testing package: hydrostatic, ultrasonic, eddy current, PMI, impact test, intergranular corrosion?
Documentation: EN 10204 3.1 or 3.2? Need third-party inspection (SGS / BV / TÜV / DNV)?
End use: boiler, heat exchanger, ethylene furnace, nuclear SG, aerospace — affects the traceability and ASME Section number.
Delivery: by date, by shipment, by project milestone? Ex-works, FOB, CIF, DDP?
Packaging: wooden box seaworthy export, plastic end-caps, bundle strapping, fumigated?

10. Frequently Asked Questions

Q1. Can I weld ASTM B167 tube to standard austenitic stainless steel (304H, 321H)?

Yes, but you need a nickel-base filler (ERNiCrMo-3 for N06600 to stainless, ERNiCrCoMo-1 for N06690) and a controlled preheat/interpass. The weld will be a transition joint — design the joint so the higher-alloy side is the corrosion-exposed side.

Q2. Is Alloy 600 still acceptable for new PWR steam generators?

For new plants, the international consensus is N06690. N06600 is permitted for non-nuclear high-temperature service and is still in service in many operating PWRs, but it is no longer the preferred material for new SG tubes.

Q3. What is the lead time for a typical 5-ton order of N06600 tube in 25 × 2.5 mm?

From the EZ Steel Industrial Cangzhou mill, 25–35 days for a mill-confirmed size that is in regular production, plus 7–10 days for sea freight to most major ports. Custom sizes that require a new piercing or rolling campaign can add 20–30 days.

Q4. How do I confirm I am getting genuine N06600, not a look-alike?

Ask for the chemistry on the MTR (Ni must be ≥72% and Cr 14–17% per ASTM B167) and demand a PMI scan on each tube. A handheld XRF will give you the Ni/Cr/Fe reading in 2 seconds and is now standard at most receiving inspections.

Q5. Can EZ Steel Industrial supply B167 tube in U-bend form?

Yes. The Lishui facility runs a U-bending line for austenitic stainless and nickel-alloy tube, with post-bend solution anneal and hydrostatic retest. Bending radius, R, is typically 1.5× to 3× OD.

11. Sourcing from a Mill-Direct Manufacturer: What That Actually Means

"Mill-direct" is one of the most overused phrases in the B2B pipe business. In a genuine mill-direct relationship, the supplier controls three things: (1) the raw material — the billet, bloom or hollow that goes into the tube; (2) the forming process — hot piercing, cold pilgering, cold drawing; and (3) the heat treatment, testing and finishing. EZ Steel Industrial operates that full chain across three sites — Cangzhou for alloy steel inventory and custom fittings, Yangzhou for large-diameter carbon and alloy steel pipe, and Lishui for stainless and copper-nickel corrosion-resistant materials. The combined capacity is 480,000 tonnes per year with 500+ employees, which is large enough to handle both project-lot retubing orders and recurring distributor replenishment.

For a B167 order, that mill-direct capability translates into:

Single point of accountability for chemistry, MTC, and heat-number traceability.
In-house NDT — ultrasonic, eddy current, hydrostatic, PMI, with documented calibration.
Bundling of pipe fittings, flanges, U-bends and finned tubes in matching or compatible alloys.
Documentation support for ASME Section I/III/VIII, PED, RCC-M and other regulatory regimes.
Multilingual project coordination (English, Chinese, Spanish, Russian, Arabic) for cross-border shipments.

Need ASTM B167 Ni-Cr-Fe alloy tube on your next project?

Send your inquiry to the EZ Steel Industrial export team. We support b167 ni-cr-fe alloy tube in UNS N06600, N06601, N06690, N06693 and N06625 — seamless tube, seamless pipe, U-bent and finned — with EN 10204 3.1 / 3.2 MTR, third-party inspection on request, and FOB / CIF / DDP terms from China to any major port.

Email: export@ezsteelpipe.com | Phone: +86 731 8870 6116 | Office: No. 199 Xiangfu Road, Yuhua Industrial Zone, Changsha, China

Attach your specification, the MTR requirements, and the delivery window. We will reply with a firm technical offer and a sample MTR within two working days.

Reference: ASTM B167 / B167M, ASME SB167, EN 10204, ASME B36.19, ASME B16.9, ASME B16.5, RCC-M Section II. Information in this article is provided for general B2B sourcing guidance and is not a substitute for the latest edition of the standard or the manufacturer's actual MTR.