ASTM B407 Incoloy 800HT UNS N08811 Nickel Alloy Seamless Pipe with High

ASTM B407 Incoloy 800HT UNS N08811 Seamless Pipe

Incoloy 800HT seamless pipe is a high-temperature nickel-iron-chromium alloy pipe identified by UNS N08811 and supplied to ASTM B407 requirements.

Unlike conventional stainless steel piping, Incoloy 800HT is selected primarily when a piping component must remain suitable for prolonged exposure to elevated temperature while maintaining resistance to oxidation and carburizing conditions. Its controlled carbon and aluminum-plus-titanium content, together with the required metallurgical condition, gives the grade its characteristic high-temperature behavior.

The seamless construction is suitable for process systems where a welded longitudinal seam is not required by the design. Pipe dimensions, manufacturing condition, heat treatment, end preparation and inspection can be specified according to the project requirements.

UNS N08811 is the material designation associated with Incoloy 800HT.

The alloy belongs to the nickel-iron-chromium family. Nickel and chromium provide the basic alloy system for high-temperature oxidation and corrosion resistance, while the controlled carbon and aluminum-plus-titanium ranges are important to the grade's elevated-temperature mechanical behavior.

For engineering and procurement purposes, the following names may be encountered for the same material:

• Incoloy 800HT
• Alloy 800HT
• UNS N08811
• 1.4959

When a purchase specification specifically requires UNS N08811, the material should be ordered and documented against that designation rather than simply identifying the product as "Incoloy 800."

The chemical composition of UNS N08811 is controlled within the ASTM B407 material specification.

The Al + Ti range is one of the useful indicators when distinguishing 800HT from the more general Alloy 800 grade. For project supply, the applicable edition of ASTM B407 and the purchase specification should be used as the final reference for material acceptance.

Material selection for high-temperature piping is not based on temperature alone. Long exposure to heat can change the mechanical behavior of a material, particularly when the component is continuously subjected to internal pressure or external loading.

For this reason, Alloy 800HT is generally considered when the service involves a combination of:

• Elevated operating temperature
• Long-duration exposure
• Mechanical loading
• Oxidizing atmospheres
• Carburizing environments
• Requirements for creep and stress-rupture resistance

The controlled composition of N08811 is intended to provide a material condition suitable for these types of service.

Actual allowable temperature and pressure must always be determined from the applicable design code, material data, process conditions and engineering calculations.

The three grades are closely related, but they should not be treated as identical materials.

If the project specification calls for UNS N08811, using N08800 or N08810 simply because the alloys belong to the same family should not be assumed acceptable.

The production route depends on the required pipe dimensions and supply condition.

The exact manufacturing route should be selected according to the ordered dimensions and ASTM B407 supply requirements rather than applying one manufacturing method to every size.

For seamless alloy pipe, dimensional accuracy is important for both fabrication and installation.

Inspection can include:

• Outside diameter
• Wall thickness
• Length
• Straightness
• End squareness
• Bevel dimensions
• Surface condition

For project orders, dimensional tolerances are checked against the applicable specification and the dimensional standard stated in the purchase order.

Typical room-temperature minimum mechanical requirements for UNS N08811 under ASTM B407 include:

These values describe room-temperature mechanical requirements. They should not be interpreted as direct allowable values for high-temperature design.

For elevated-temperature piping, the design engineer should additionally consider creep, stress rupture, operating temperature, design pressure, service duration and the applicable construction code.

For 800HT, metallurgical condition is an important part of the material specification.

The alloy is intended for applications where long-term exposure to elevated temperature can make time-dependent deformation a design consideration. Therefore, grain structure and heat treatment are not simply manufacturing details; they form part of the material's suitability for its intended service.

This is one reason why a project requiring ASTM B407 UNS N08811 should be purchased against the complete material specification rather than described only by the commercial name "Incoloy 800."

Incoloy 800HT seamless pipe can be supplied with different end conditions according to the fabrication requirements.

Plain End
Suitable for machining, socket-type preparation or further fabrication where specified.

Beveled End
Used when the pipe will be prepared for butt welding. Bevel geometry should follow the project welding or fabrication specification.

Cut-to-Length
Fixed-length pipe can be supplied when required for fabrication or spool production.

Surface condition depends on the manufacturing route and finishing requirements. Additional surface treatment or cleaning can be discussed for specific applications.

Inspection requirements can be agreed according to ASTM B407, project specifications and the purchaser's inspection plan.

Available inspection items may include:

For project orders, inspection requirements can be incorporated into an Inspection and Test Plan (ITP).

Traceability is important for nickel alloy piping used in critical process equipment.

The supplied pipe can be identified through:

• Heat number
• Material grade
• Pipe size
• Quantity
• Test results
• Heat-treatment records where applicable
• Mill Test Certificate

The heat number can be maintained from material production through final inspection and documentation.

The documentation package can be prepared according to the purchase requirements.

Typical documents include:

• EN 10204 3.1 Material Test Certificate
• Chemical analysis
• Mechanical test results
• Heat-treatment information
• Dimensional inspection records
• NDT reports when applicable
• PMI report when required
• Third-party inspection documentation when specified

For orders involving special documentation, the required certificate level should be confirmed before production.

Incoloy 800HT seamless pipes are prepared for international shipment according to pipe size, length, surface condition and transportation method.

Typical export packing may include:

• Plastic protection
• Pipe bundling
• Steel straps
• End protection
• Wooden supports
• Plywood cases where required
• Seaworthy export packaging

For long-length pipes, packaging can be adjusted to reduce movement and potential surface damage during loading and transportation.