What are the mechanical properties of b167 ni-cr-fe alloy tube?

When you specify a nickel-chromium-iron alloy tube for a high-temperature or corrosive service, the first question your project engineer will ask is simple: "Will it hold the line?" ASTM B167 exists to give that question a clear, answerable form. This article walks through the mechanical properties required by ASTM B167, what those values mean on a real project, and how [EZ Steel Industrial's ASTM B167 Ni-Cr-Fe alloy tube](https://www.ezindustrialtube.com/products/608.html) program is built around them.

What ASTM B167 Covers

ASTM B167 is the standard specification for seamless pipe and tube made from nickel-chromium-iron alloys. The current edition lists nine UNS designations: N06600 (Inconel 600), N06601 (Inconel 601), N06603, N06617, N06690 (Inconel 690), N06693, N06025 (Alloy 602 CA), N06045 (Alloy 45TM), and N06696. The ASME equivalent is SB-167, adopted into Section II, Part B of the Boiler and Pressure Vessel Code for code-stamped pressure equipment.

B167 is intentionally a "performance" standard, not a recipe. It locks down chemical composition, mechanical property minimums, dimensional tolerances, and mandatory testing (tension, hydrostatic, and chemistry), but leaves the manufacturing route (hot-worked, hot-finished, or cold-worked, followed by annealing) to the producer. That flexibility matters because the same alloy can be supplied with very different strength levels depending on whether the tube is hot-finished or cold-worked annealed.

Why Mechanical Properties Matter for Ni-Cr-Fe Tubes

For stainless or carbon steel pipe, mechanical property questions are often answered by referring to a single room-temperature value. Ni-Cr-Fe tubes are different. They are typically chosen because the service temperature, the corrosion environment, or the cyclic loading is beyond what a 300-series stainless can survive. The mechanical property table in B167 is the contract that says the tube will still hold its specified minimum yield strength, tensile strength, and ductility after that exposure.

Three mechanical properties drive almost every selection decision in B167:

• Tensile strength (Rm): the maximum stress the tube can carry before it necks. For pressure-retaining equipment, it sets the upper bound on allowable fibre stress.
• Yield strength (Rp0.2, 0.2% offset): the stress at which the material begins to deform plastically. ASME B31.3 and Section VIII use this value, often derated by a design factor, to set the maximum permissible operating pressure.
• Elongation in 2 in. or 50 mm: a measure of ductility, expressed as a percentage. It signals forming capacity (for U-bends, branch connections, cold swaging) and fracture toughness in service.

ASTM B167 Mechanical Property Requirements

The values below are the minimum property limits the standard enforces. Producers such as [EZ Steel Industrial](https://www.ezindustrialtube.com/) typically report typical values that exceed these minimums, but procurement documents and code calculations must be based on the minimums.

Notes: HW = hot-worked; HWA = hot-worked annealed; CWA = cold-worked annealed. Values are reproduced from ASTM B167 Table 2 and ASME SB-167 for the 2024 revision. Always confirm the latest edition before procurement.

What the Numbers Mean in Practice

A few practical patterns jump out of the table.

Cold-worked annealed is stronger than hot-worked annealed. For N06600, the CWA condition raises the minimum yield strength by 35 MPa (from 205 to 240 MPa) on tubes up to 5 in. OD compared with HW/HWA at the same size. Cold drawing also tightens dimensional tolerances and improves surface finish, which is why most heat-exchanger and high-pressure instrument tubing in B167 is supplied CWA. Hot-worked pipe is reserved for larger diameters where cold drawing is impractical, and that is why the standard allows a 35 MPa lower yield on the >5 in. HW/HWA size.

Larger OD means lower minimums in the HW/HWA condition. This is not a relaxation; it reflects the metallurgical reality that the heavier the wall and the larger the section, the harder it is to achieve uniform grain refinement during hot working. Engineers specifying pipe above 5 in. OD should account for the lower yield when calculating wall thickness, and may need to derate allowable pressure or move up a schedule.

The specialist grades carry higher strength ceilings. N06603, N06025, and N06045 are designed for the most extreme thermal environments. N06025 (Alloy 602 CA) carries the highest tensile strength of the family at 98 ksi (680 MPa), reflecting its aluminium + rare-earth additions and its use in furnaces operating up to 2,200 °F (1,200 °C). N06603 follows at 94 ksi (650 MPa) for similar reasons.

Ductility sits between 25% and 35%. Even the strongest grades in the family keep elongation at 25% or more. That is plenty of ductility for U-bending, flaring, and welded branch connections, and it is one of the practical advantages Ni-Cr-Fe tubes retain over higher-strength but more brittle alloys.

Allowable Fibre Stress for Pressure Design

Pressure design under ASME B31.1, B31.3, or Section VIII uses an allowable fibre stress, not the minimum tensile or yield value directly. ASTM B167 publishes those fibre-stress values so designers and inspectors can apply the same numbers on every order. They are derived from the tensile and yield minimums with a safety factor, then rounded for code use.

In pressure calculations, the standard hydrostatic test is 1,000 psi (6.9 MPa) maximum, or by agreement between the manufacturer and purchaser, 1.5× the allowable fibre stress. This is the test pressure that appears on the mill test certificate.

How the Mechanical Properties Are Verified

Every heat of B167 tube is tested in three ways. One tension test is taken per lot, where a "lot" is the same heat, nominal size, and condition. Tensile specimens are full tubular sections where geometry allows, with longitudinal strip or round specimens as fallbacks per ASTM E8. One chemical analysis is performed per heat, with check-analysis tolerances per ASTM B880. And every individual tube above 1/8 in. OD with wall thickness of 0.015 in. or more is hydrostatically tested.

At [EZ Steel Industrial](https://www.ezindustrialtube.com/), the B167 program is produced under ISO 9001 with API 5L / API 5CT product certification and PED compliance as applicable. Mill test certificates report the actual tensile, yield, and elongation values from the lot, and where the application requires, additional non-destructive testing such as ultrasonic or eddy-current inspection can be added. The full ASTM B167 tube portfolio, including N06600, N06601, N06690, and the higher-nickel grades, is detailed on the [B167 Ni-Cr-Fe alloy tube product page](https://www.ezindustrialtube.com/products/608.html).

Choosing the Right Condition and Heat Treatment

For a given alloy, the same chemistry can be delivered at very different strength levels. Three rules of thumb cover most selections:

• CWA for small-bore, high-pressure, or heat-exchanger service. The tighter tolerances, better surface finish, and higher yield strength pay off in thinner walls and tighter tube sheets.
• HWA for large-diameter process pipe. When OD exceeds 5 in. and cold drawing is impractical, hot-worked annealed pipe is the only realistic option, and the lower minimums must be accommodated in the wall-thickness calculation.
• Solution anneal, then water quench, for severe service. Producers following the standard's heat treatment recommendations typically anneal at 960–1,040 °C, hold for about 15 minutes, and water-quench to lock in the solution-annealed condition. Skipping the quench or cooling too slowly can leave carbides at the grain boundaries and reduce corrosion resistance.

Frequently Asked Questions

Does cold drawing always increase strength in B167 tubes?

For the N06600 and N06690 lines, the standard's CWA minimums are higher than the HW/HWA minimums, but the difference is modest (about 35 MPa on yield). For alloys such as N06603, N06025, and N06045, the standard does not differentiate between CWA and HWA because their strength comes from chemistry and final anneal, not from the cold-work input.

How do the B167 minimums compare with typical values?

Typical mill reports on N06600 annealed tube show tensile strength in the 580–860 MPa range and yield strength in the 240–400 MPa range, comfortably above the 550 / 205 MPa minimums. The minimums are the contractual floor; typicals are what you should expect on a routine order.

Can B167 tubes be used in nuclear service?

Yes. B167 is the underlying material standard for Ni-Cr-Fe seamless pipe and tube in nuclear plants, with N06690 being the dominant grade for PWR steam generator tubing and associated piping. The ASME SB-167 designation, combined with the Section III code stamping, is what makes a tube acceptable for nuclear installation.

What is the difference between B167 and B163?

B163 covers Ni-Cr-Fe and Ni-Fe-Cr tubes specifically for condensers and heat exchangers, with tighter surface-finish, NDE, and dimensional requirements. B167 is the broader specification for general seamless pipe and tube. For condenser and heat-exchanger bundles, B163 is typically the cited specification; for associated piping, B167.

Summary

ASTM B167 is the contract that lets a buyer, an engineer, and an inspector agree on what "strong enough" means for a Ni-Cr-Fe alloy tube. The mechanical property table in the standard defines minimum tensile strength (550–680 MPa depending on grade), minimum 0.2% offset yield strength (170–300 MPa), and minimum elongation (25–35%) for nine UNS designations across hot-worked, hot-worked annealed, and cold-worked annealed conditions. The allowable fibre-stress table, which runs from 16,700 to 24,500 psi, drives the pressure design calculation under ASME B31.1, B31.3, and Section VIII.

For procurement, the practical checklist is short: pick the UNS designation by service environment, pick the condition by tube size and pressure class, and require a mill test certificate that reports the actual tensile, yield, and elongation values from the lot. When that is in place, the [ASTM B167 Ni-Cr-Fe alloy tube](https://www.ezindustrialtube.com/products/608.html) supplied by EZ Steel Industrial is ready to install in the boiler, heat exchanger, reformer outlet, or process line it was ordered for.