Introduction
Inconel 600, designated UNS N06600, is a nickel-chromium-iron alloy supplied as seamless and welded tubing for service that combines elevated temperature with corrosive media. The alloy offers high strength, oxidation resistance, scale resistance, and resistance to chloride-induced stress corrosion cracking, together with excellent weldability. These properties make it a standard material for pressure vessels, heat exchangers, furnace components, and high-temperature process piping across chemical processing, aerospace, nuclear, and heat-treatment industries.
Chemical Composition
The composition of Inconel 600 tubing is defined by the governing specification, with typical limits of nickel 72.00 percent minimum, chromium 14.00 to 17.00 percent, iron 6.00 to 10.00 percent, carbon 0.15 percent maximum, manganese 1.00 percent maximum, silicon 0.50 percent maximum, sulfur 0.015 percent maximum, and copper 0.50 percent maximum. The high nickel content provides resistance to chloride stress corrosion cracking, and the chromium content supports oxidation and scale resistance at elevated temperatures.
Mechanical and Physical Properties
Typical annealed mechanical properties reported for Inconel 600 are approximately 655 MPa (95 ksi) tensile strength, 310 MPa (45 ksi) 0.2 percent yield strength, and 40 percent elongation, with a density of about 8.47 g/cm3 and a melting point near 1413 °C (2580 °F). The alloy can be strengthened through cold working, which increases strength and hardness while reducing ductility. For hot working, the typical range is approximately 870 to 1230 °C (1600 to 2250 °F): heavy-duty working is performed between 1040 and 1230 °C (1900 to 2250 °F), while light-duty working can be carried out at temperatures as low as 870 °C (1600 °F).
Machining, Cold Working, and Heat Treatment
Inconel 600 is suitable for a variety of machining and fabrication methods, including welding and cold working. Cold working is used to improve strength and hardness where the design requires it. Annealing improves ductility and produces a fine-grained structure, and different heat treatment schedules can be used to optimize specific properties such as creep strength and fracture strength. Because the alloy work-hardens during machining, lower cutting speeds and heavier feeds are generally recommended compared with standard austenitic stainless steel, and appropriate tooling should be selected to machine under the work-hardened surface layer.
Common Applications
In chemical processing, Inconel 600's resistance to a variety of corrosive media makes it an ideal material for heat exchangers, pipes, and reactors. In aerospace, it is used in engine and fuselage components that must withstand high temperatures, such as exhaust bushings and turbine seals. In nuclear energy, its excellent resistance to corrosion by high-purity water makes it a standard structural material for reactor hardware. In heat treatment, it is used for furnace components such as rotary kilns, muffle furnaces, and roller hearth furnaces, and in food processing it supports hygiene in steam boilers and reactors. The alloy is also valued for oxidation resistance in applications reported up to about 1093 °C (2000 °F), particularly where loads are low.
Specification Notes
Inconel 600 tubing should be specified by UNS number, product form, outside diameter, wall thickness, length, and condition, against the governing standard such as ASTM B167 for seamless pipe or ASTM B163 for seamless tube, with ASME SB equivalents for code work. Certified mill test reports should confirm chemical composition, mechanical properties, and heat treatment. For welded tubing, the applicable welded specifications should be selected, and weld quality should be verified by the required nondestructive examination.
FAQ
Q: What temperature can Inconel 600 tubing withstand?
A: The alloy offers oxidation resistance reported up to about 1093 °C (2000 °F) in lightly loaded service, while the typical hot working range is 870 to 1230 °C (1600 to 2250 °F). Allowable service temperature depends on pressure, media, and code requirements.
Q: What is Inconel 600 made of?
A: UNS N06600 contains at least 72 percent nickel, 14 to 17 percent chromium, and 6 to 10 percent iron, with low carbon, manganese, silicon, sulfur, and copper limits.
Q: Is Inconel 600 tubing resistant to chloride stress corrosion cracking?
A: Yes. The high nickel content gives Inconel 600 significantly better resistance to chloride-induced stress corrosion cracking than conventional austenitic stainless steels in many environments.
Q: Can Inconel 600 tubing be cold worked to increase strength?
A: Yes. The alloy can be strengthened by cold working, and it can be welded and annealed to restore ductility and produce a fine-grained structure.
Q: What standards cover Inconel 600 tubing?
A>Seamless pipe is covered by ASTM B167 and seamless tube by ASTM B163, with corresponding ASME SB editions, along with related welded tube specifications such as ASTM B516 and B517.
Q: Where is Inconel 600 tubing commonly used?
A: Chemical processing heat exchangers and reactors, aerospace exhaust bushings and turbine seals, nuclear reactor hardware, furnace components, and food processing steam equipment.
