What Is ASME SB407 UNS N08810 Pipe?
ASME SB407 UNS N08810 is the specification for seamless and welded nickel-iron-chromium pipe and tube of Incoloy 800H. The alloy is a modified version of Alloy 800 (UNS N08800) with controlled carbon, aluminum and titanium additions, and it is solution annealed at high temperature to produce a coarse-grained structure that maximizes creep resistance. This combination makes UNS N08810 pipe a standard choice for equipment that operates at sustained high temperature and pressure, such as hydrocarbon processing, heat exchangers and offshore oil and gas systems.
Chemical Composition
UNS N08810 is specified with nickel 30.0-35.0%, chromium 19.0-23.0%, iron 36.5% minimum, manganese up to 1.5%, carbon 0.05-0.10%, copper up to 0.75%, silicon up to 1.0%, sulfur up to 0.015%, aluminum 0.15-0.60% and titanium 0.15-0.60%. The controlled carbon range and the aluminum and titanium additions distinguish 800H from the standard 800 grade and are the basis of its improved high-temperature mechanical properties.
High-Temperature Strength
UNS N08810 exhibits excellent creep and stress-rupture properties above about 593°C (1100°F), which is critical for preventing deformation and failure under sustained high temperature and pressure. The coarse grain structure produced by high-temperature annealing is essential to this performance, because grain size directly affects creep resistance in this alloy system. Designers should note that UNS N08810 and UNS N08811 are related but not identical: materials produced to N08810 cannot be certified as N08811 unless they meet the additional requirements of that designation, which carries higher allowable design stresses in some codes.
Corrosion Resistance
Because of its high nickel content, Incoloy 800H resists oxidation, sulfidation and carburization, resists chloride ion stress corrosion cracking, and withstands a wide range of corrosive media including acidic and alkaline environments. In offshore service, this protects process piping and heat exchanger tubing against seawater, sour fluids and combustion gas attack. The alloy also retains good mechanical properties at cryogenic temperatures, which broadens its service envelope.
Applications on Offshore Oil Platforms
The harsh offshore environment, with high pressure, high temperature and corrosive seawater, requires specialized materials. ASME SB407 UNS N08810 pipes are used in high-temperature process systems that transport hot fluids and gases, heat exchangers that heat or cool process fluids, downhole tubing for drilling and production, and equipment components exposed to corrosion and high-temperature erosion in the range of 593-980°C (1100-1800°F). The alloy's combination of creep strength and corrosion resistance keeps maintenance intervals long and failure risk low.
Procurement and Quality Considerations
When procuring UNS N08810 pipe, confirm the governing specification edition of ASME SB407, the product form and size range, the heat treatment condition, and the required testing such as hydrostatic, eddy current or ultrasonic examination. Request a material test certificate showing the heat number, chemical composition and mechanical properties, and verify that the grain size and anneal temperature meet the requirements for the 800H designation. For pressure-retaining offshore service, third-party inspection and traceability are standard practice.
FAQ
Q: What is the difference between N08810 and N08811?
A: Both are high-temperature variants of Alloy 800, but UNS N08811 carries higher allowable design stresses in some codes. Material produced to N08810 cannot be certified as N08811 unless it meets the additional requirements of that designation.
Q: What is Incoloy 800H?
A: Incoloy 800H is the trade designation for Alloy 800 with controlled carbon, aluminum and titanium, solution annealed for a coarse grain structure and high creep strength; it corresponds to UNS N08810.
Q: What standard covers this pipe?
A: ASME SB407/ASTM B407 covers seamless and welded nickel-iron-chromium alloy pipe and tube, including UNS N08810.
Q: Why is UNS N08810 used offshore?
A: It combines creep and rupture strength above 593°C with resistance to oxidation, sulfidation, carburization and chloride stress corrosion cracking, which suits high-temperature process systems and heat exchangers in marine environments.
Q: What is the carbon content of UNS N08810?
A: The controlled carbon range is 0.05-0.10%, with aluminum and titanium additions of 0.15-0.60% each, which together provide the improved high-temperature properties of the 800H grade.
Q: Can UNS N08810 pipe be welded?
A: Yes. The alloy is readily welded with matching nickel-based filler metal using standard arc processes, and welded pipe is available to the same specification with appropriate procedure qualification.
