ASTM B407 N08800 Seamless Pipe Introduction
ASTM B407 N08800 seamless pipe is a nickel-iron-chromium alloy seamless pipe produced in accordance with the American Society for Testing and Materials (ASTM) B407 standard. Its corresponding designation is UNS N08800 (Incoloy 800).
The alloy's core chemical composition requirements are 30%-35% nickel (Ni), 19%-23% chromium (Cr), 0.15%-0.60% aluminum (Al) and 0.15%-0.60% titanium (Ti), with carbon (C) controlled to ≤0.10%, and the balance being iron (Fe). Typical mechanical properties in the annealed state include a tensile strength of at least 520 MPa, a yield strength of at least 205 MPa, and an elongation of at least 30%.
N08800 seamless pipe offers excellent resistance to high-temperature oxidation and carburization, as well as good corrosion resistance, particularly in environments with moderately concentrated nitric acid. Therefore, it is often used in the manufacture of chemical process equipment such as nitric acid coolers and heat exchangers. In addition, its high nickel content effectively resists stress corrosion cracking, extending its application to heat treatment equipment and nuclear power plant components.
Incoloy 800 seamless pipe undergoes solution treatment to ensure uniform microstructure and stable performance, and can be welded using processes such as tungsten inert gas welding. N08800 seamless pipe typically comes in sizes ranging from 10mm to 762mm in outer diameter and 2.0mm to 140mm in wall thickness.
ASTM B407 N08800 Seamless Pipe Applications
Chemical Industry
In chemical production, N08800 seamless pipe, due to its excellent acid corrosion resistance, is often used in the manufacture of equipment such as nitric acid coolers, acetic anhydride cracking tubes, heat exchanger piping, and reactors. It performs particularly well in nitric acid environments with concentrations up to 65% and temperatures below 50°C, keeping corrosion rates to extremely low levels. This effectively ensures safe and stable transportation and handling of highly corrosive media, reducing leakage risks and maintenance costs.
Oil and Gas Industry
In the extraction, processing, and transportation of oil and gas, N08800 seamless pipe is widely used in key areas such as oil well casing, gathering pipelines, process air cooling heat exchangers, and heating furnace tubes. These components often must withstand high temperatures, high pressures, and corrosive media such as hydrogen sulfide and chlorides. The material's high nickel content provides excellent resistance to chloride-ion stress corrosion cracking, while its high chromium content provides excellent resistance to oxidation and carburization, ensuring long-term reliable operation under harsh operating conditions.
Power Industry
In the power industry, N08800 seamless pipe is an ideal material for nuclear power plant steam generator piping and thermal power plant boiler superheater and reheater piping. It exhibits excellent resistance to stress corrosion cracking in high-temperature, high-pressure water and can withstand long-term high-temperature creep and fatigue loads.
Aerospace
In the aerospace industry, N08800 alloy, due to its high strength, high-temperature resistance, and corrosion resistance, is often used in the manufacture of engine turbine blades, combustion chambers, and other high-temperature components of propulsion systems.
Environmental Protection and Energy
N08800 seamless pipe also plays an important role in environmental protection and new energy fields, such as seawater desalination plants, flue gas desulfurization systems, and wastewater treatment. For example, in desalination projects, its excellent chloride ion corrosion resistance effectively combats the highly corrosive nature of seawater; in flue gas desulfurization environments, it resists corrosion from media such as sulfides.
ASTM B407 N08800 Properties
Corrosion Resistance
ASTM B407 N08800 seamless pipe offers excellent corrosion resistance, particularly in oxidizing media and high-temperature environments. Its chromium content forms a dense Cr₂O₃ oxide film on the surface, effectively resisting attack by media such as nitric acid and organic acids. In conditions of moderate nitric acid concentrations and temperatures ≤50°C, the annual corrosion rate can be less than 0.1 mm.
Concurrently, its high nickel content provides excellent resistance to stress corrosion cracking, particularly in chloride environments, low-concentration sodium hydroxide solutions, and high-temperature, high-pressure water.
High-Temperature Performance
One of the alloy's core strengths is its high-temperature stability, maintaining performance up to 1100°C. Its oxidation resistance persists up to approximately 800°C, while its resistance to carburization and sulfidation enables it to withstand industrial atmospheres containing impurities.
High-temperature strength is primarily due to solid solution strengthening. While the tensile strength remains approximately 300 MPa at 700°C, the strength gradually decreases with increasing temperature. This property makes it suitable for components exposed to long-term high temperatures and high pressures, such as nuclear power plant evaporator piping and waste heat boiler heat exchanger tubes.
Mechanical Properties
In the solution-treated state, this material exhibits a typical room-temperature tensile strength of no less than 520 MPa, a yield strength of no less than 205 MPa, and an elongation exceeding 35%. Its work hardening rate is higher than that of conventional austenitic stainless steel, so intermediate annealing is necessary during cold working.
Regarding high-temperature short-term mechanical properties, the tensile strength is approximately 360 MPa at 500°C and approximately 300 MPa at 600°C, demonstrating excellent thermal toughness.
Physical Properties
N08800 alloy has a density of approximately 7.95–8.0 g/cm³ and a melting temperature range of 1350°C to 1400°C. Its specific heat capacity is 455 J/kg·°C, its elastic modulus is approximately 206 GPa, its Poisson's ratio is 0.3, and it is non-magnetic.
Manufacturing and Processing
This seamless pipe is formed by hot rolling, cold drawing, or cold rolling, and undergoes rigorous solution treatment to ensure structural homogeneity.
It has excellent weldability and can be welded using methods such as tungsten inert gas welding and plasma arc welding. ERNiCr-3 welding wire is recommended, and a shielding gas of argon mixed with a small amount of nitrogen is recommended to control oxidation. To maximize corrosion resistance, the finished product is pickled or electropolished to reduce surface roughness.
Conclusion
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