What Is ASTM B167 UNS N06600 Seamless Tube?
ASTM B167 covers seamless nickel-chromium-iron alloy tubes for general corrosion-resisting and heat-resisting service, and UNS N06600 (commonly known as Inconel 600) is one of the most widely specified grades under this standard. The alloy combines a high nickel content with chromium and iron to deliver excellent high-temperature resistance, oxidation resistance and resistance to a broad range of corrosive environments. Tubes are manufactured by hot or cold working and are routinely subjected to tensile and hydrostatic testing to verify mechanical properties and pressure integrity.
While N06600 is not the newest or the strongest nickel alloy, its proven performance and wide availability make it a staple in industries ranging from nuclear power to petrochemical processing.
Chemical Composition of UNS N06600
Per typical ASTM B167 requirements, the composition of N06600 tube is: nickel 72.0% min, chromium 14.0-17.0%, iron 6.0-10.0%, carbon 0.15% max, manganese 1.00% max, silicon 0.50% max, sulfur 0.015% max and copper 0.50% max.
The high nickel content gives the alloy strong resistance to chloride-induced stress corrosion cracking and to caustic environments, while chromium provides oxidation and scaling resistance at elevated temperatures. Iron contributes to the overall balance of strength and fabricability.
Mechanical and Physical Properties
Annealed N06600 seamless tube typically exhibits a minimum tensile strength of about 655 MPa, a minimum yield strength (0.2% offset) of about 310 MPa and elongation of about 40%, with a density of approximately 8.47 g/cm3 and a melting range around 1413°C.
The alloy retains good mechanical strength at both high and ultra-low temperatures, which is why it is also specified for cryogenic equipment. It remains nonmagnetic from low temperature up to its Curie point, an important feature for instrumentation and electronic applications. Resistance to pure and ultrapure water is another distinguishing characteristic.
Corrosion Resistance Highlights
N06600 resists organic and inorganic acids across many concentrations, shows superior resistance to chloride stress corrosion cracking compared with many stainless steels, and performs well in alkaline environments such as sodium hydroxide, making it a common choice for alkaline evaporators. It also withstands chlorine and hydrogen chloride service, as well as high-temperature oxidation in air.
Common Applications
Heat exchangers and boilers: high-pressure, high-temperature service in petrochemical and chemical plants.
Nuclear reactors: a standard structural material for reactor components.
Chemical processing: equipment handling chlorine, hydrogen chloride and strong alkalis.
Cryogenic applications: components exposed to sub-zero temperatures where strength must be retained.
Other uses: furnace components, thermocouple sheaths, electronic parts such as tube supports and springs, and alkaline evaporators.
Equivalents and Specification Notes
UNS N06600 has several international equivalents used across projects: W.Nr 2.4816 and DIN NiCr15Fe in Germany, JIS NCF 600 in Japan, BS NA 13 in the United Kingdom and EN NiCr15Fe in Europe. When specifying, always confirm the governing standard, product form and test requirements, because bar, plate and tube versions of the alloy are covered by different ASTM documents such as B166, B168 and B167.
FAQ
Q: What is the difference between ASTM B167 and ASME SB167?
A: ASME SB167 is the ASME Boiler and Pressure Vessel Code version of the same seamless tube specification. SB167 material is permitted for code construction, while B167 covers the same requirements for general industrial use.
Q: Can N06600 tube be used at cryogenic temperatures?
A: Yes. The alloy maintains good mechanical properties at ultra-low temperatures and is frequently specified for cryogenic liquid handling equipment.
Q: Is Inconel 600 magnetic?
A: No. N06600 remains nonmagnetic from low temperatures up to its Curie point, which makes it suitable for sensitive instrumentation and electronic components.
Q: What testing is typically required for ASTM B167 tubes?
A: Tensile testing and hydrostatic testing are commonly required, along with chemical composition verification. Additional nondestructive examination can be specified by the purchaser.
Q: Why is N06600 preferred over stainless steel in some heat exchangers?
A: N06600 offers superior resistance to chloride stress corrosion cracking and to caustic environments, and it retains strength at much higher temperatures than standard stainless steels.
Q: Does N06600 resist seawater?
A: N06600 has limited resistance to seawater and stagnant chloride solutions; for aggressive marine service, higher-alloyed grades with molybdenum are usually recommended instead.
