What are the mechanical properties of b407 incoloy 800 tube?

When engineers specify piping for high-temperature furnaces, reformers, and heat exchangers, one of the first questions they ask is about the mechanical properties of the material. For the nickel-iron-chromium alloy family covered by ASTM B407, the answer depends on which grade you choose, how the tube was processed, and the temperature at which it will operate. This article explains the mechanical properties of B407 Incoloy 800 tube in practical terms, so you can ｓｅｌｅｃｔ the right grade and condition for your project.

What Is ASTM B407 Incoloy 800 Tube?

ASTM B407 is the standard specification for seamless pipe and tube made from nickel-iron-chromium alloy. It covers the Incoloy 800 family, including UNS N08800 (Incoloy 800), UNS N08810 (Incoloy 800H), and UNS N08811 (Incoloy 800HT), as well as N08801 and N08120. These alloys sit between austenitic stainless steels, which lack high-temperature strength, and high-nickel alloys such as Inconel 600, which cost considerably more. That balance makes them the workhorse choice for industrial heating, petrochemical reforming, and power generation applications.

The specification defines chemical composition, mechanical properties, grain size requirements, dimensional tolerances, heat treatment, and testing. Tubes are supplied in cold-worked, annealed, or hot-finished conditions, and the mechanical properties you can rely on are tied directly to that condition.

Chemical Composition That Drives Performance

The mechanical behaviour of Incoloy 800 comes from a carefully balanced composition. The alloy contains 30.0-35.0% nickel, 19.0-23.0% chromium, and a minimum of 39.5% iron, with small additions of carbon, manganese, silicon, aluminium, and titanium. Nickel provides strength and resistance to oxidation and carburisation, while chromium adds corrosion resistance and high-temperature scaling resistance. The controlled carbon and grain size in the H and HT grades are what give them their superior creep strength above 593°C (1100°F).

Room-Temperature Mechanical Properties

ASTM B407 sets minimum room-temperature mechanical properties that vary by grade and condition. These are the values you should use when checking a mill certificate or comparing supplier quotations.

In practice, annealed Incoloy 800H tubes typically deliver well above these minimums, with tensile strength in the range of 580-650 MPa and yield strength of 240-280 MPa. Elongation usually falls between 35% and 45%, which reflects the excellent ductility of the stable austenitic structure.

800 vs 800H vs 800HT: What Changes in Mechanical Terms

The three main grades look similar at room temperature, but their mechanical properties diverge sharply at elevated temperature. Incoloy 800 (N08800) is the general-purpose grade, suitable for service up to about 593°C (1100°F). Incoloy 800H (N08810) restricts carbon to 0.05-0.10% and requires a coarse grain size of ASTM No. 5 or coarser, which improves creep and rupture resistance above 593°C. Incoloy 800HT (N08811) goes further, controlling carbon to 0.06-0.10% and holding the combined aluminium plus titanium content at 0.85-1.20% to enable precipitation strengthening during service.

The practical result is that at 870°C (1600°F), 800HT has roughly 20-30% higher 100,000-hour rupture strength than 800H, which in turn is significantly stronger than standard 800. If your application runs above 593°C, the H or HT grade is the mechanically correct choice.

Elevated-Temperature Mechanical Properties

For furnace tubes, reformer coils, and heat exchanger service, room-temperature data is not enough. The table below shows typical elevated-temperature properties for Incoloy 800H, which illustrate how the alloy retains useful strength far beyond the limits of stainless steel.

Note that these are typical values, not code minimums. For pressure vessel design above 600°C, engineers should use the allowable stresses published in ASME Code Case 2225, which are derived from the 100,000-hour creep rupture strength with an appropriate safety factor.

Creep and Rupture Resistance

Above 593°C, creep becomes the governing design criterion. Incoloy 800H maintains useful creep strength up to about 900°C, which is why it is specified for steam methane reformer outlet manifolds, ammonia reformer transfer lines, ethylene cracker radiant coils, and petrochemical furnace tubes. The coarse grain structure and controlled carbide precipitation at grain boundaries slow diffusion-controlled deformation, giving the alloy long, predictable service life under sustained load.

Testing and Quality Assurance

ASTM B407 requires chemical analysis, tension testing, and hydrostatic or eddy current testing on every lot. For the H and HT grades, a grain size test per lot is mandatory and must meet ASTM No. 5 or coarser. When sourcing B407 Incoloy 800 tube for critical service, always request the mill test certificate, verify the heat treatment records, and confirm grain size verification. A reliable supplier will provide full traceability from heat analysis to final inspection.

Choosing the Right Tube for Your Application

The mechanical properties of B407 Incoloy 800 tube make it the preferred material for high-temperature and high-corrosion environments. For general heat exchanger tubing and process piping up to 593°C, standard Incoloy 800 is a cost-effective choice. For reformer tubes, furnace coils, and any service above 593°C where creep and rupture resistance matter, specify Incoloy 800H or 800HT. When you need a dependable supply of heat exchanger tube or high-performance alloy steel tube, working with a manufacturer that can supply certified B407 material with complete documentation saves time and reduces project risk.

If you are planning a project that requires B407 Incoloy 800 tube, contact EZ Steel Industrial for certified material, mill test certificates, and expert guidance on grade selection and specification.