UNS N06686 Composition|Process|Application|Strength
Inconel 686(UNS N06686/W.Nr. 2.4606)
Inconel 686/N06686 is a NI-Cr-Mo solid solution strengthened corrosion-resistant nickel-based alloy. It has outstanding corrosion resistance in harsh corrosive environments. It is mainly used in chemical processing, pollution control, papermaking, industry and municipal waste. Heat exchangers, reaction vessels, transfer pipes, etc. for processing.
According to Huntington Specialty Materials of the United States, Inconel 686 alloy, which has excellent corrosion resistance, has replaced the K-500 alloy used on U.S. Navy ships as connectors. Alloy 686 is a solid solution strengthened alloy that obtains high strength through cold working. In particular, the cold-worked 686 alloy shows outstanding hydrogen embrittlement resistance and corrosion resistance, such as excellent strength, ductility and toughness. 1.3×33cm (0.5×13 inches) bolts are made from cold-processed 686 alloy rods with a diameter of 38Inm (15 inches) and have a standard R1Tr ultimate tensile strength of 993MPa. These processed bolts have processed connectors and wedges. The middle part of the tension test showed good performance.
Inconel686(UNS N06686/W.Nr. 2.4606)
Cr19.0-23.0
F Less than or equal to 2.0
Mo15.0-17.0
Ti0.02-0.25
W3.0-4.4
C Less than or equal to 0.01
Mn Less than or equal to 0.75
S Less than or equal to 0.02
Si Less than or equal to 0.08
P Less than or equal to 0.04
Density (g/cm3) 8.73
Melting point ( degree ) 1338-1380
Specific heat (J/kg- degree ) 373
Resistivity (ohm circ mil/ft) 744.4
Ways to improve the purity and homogenization of nickel-based alloy rod blanks
In the past decade or so, the demand for nickel-based alloy materials in high-end equipment manufacturing outside China's aerospace industry has grown rapidly with the improvement of industrialization level. At the same time, high-end equipment manufacturing has increasingly higher requirements for the quality of nickel-based alloy materials. High purity, homogenization and long service life have become the eternal themes in the development of nickel-based alloy materials. Moreover, the demand for oversized components made of nickel-based alloy materials in the fields of nuclear energy, electric power, and petrochemicals continues to increase, which objectively makes it difficult to improve the purity and homogenization of nickel-based alloy materials. To this end, technological transformation and process development of equipment such as VOD furnaces, vacuum induction furnaces (VIM), vacuum electric arc furnaces (VAR), inert atmosphere electroslag furnaces (ESR), fast forging machines, and radial forging machines have been carried out to adapt to market requirements. Demand for high-quality nickel-based alloy materials. This has promoted the introduction of nickel-based alloy materials into the material selection and application of domestic nuclear power equipment, flue gas turbines, industrial gas turbines, oil and gas mining, refining and chemicals, transportation, environmental protection, and 700 degree ultra-supercritical power generation unit projects. In view of the fact that the quality of forged nickel-based alloy bar blanks determines the structure and performance of downstream production discs, blades, ring forgings, rotors, valves, and seamless tube products, this article studies ways to improve the purity and homogenization of nickel-based alloy materials. .
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Nickel-based alloy materials for non-aerospace applications
Nickel-based alloys use nickel (or add some iron or cobalt) as the austenite matrix, selectively add chromium, tungsten, molybdenum, and niobium elements for solid solution strengthening, and selectively add aluminum, titanium, and niobium elements to form a second Phase precipitation strengthening, a type of special metal material that selectively adds trace elements such as boron, cerium, lanthanum, magnesium, and zirconium to purify grain boundaries. Nickel-based alloys are divided into deformed alloys and cast alloys according to their forming methods; they are divided into solid solution-strengthened alloys and age-strengthened alloys according to their strengthening methods. In high-end equipment industries other than aerospace (Table 1), the usage environment of nickel-based alloys is usually divided into two categories. One type is used in high-temperature oxidation conditions above 600 degree , and the other type is used in corrosive media below 600 degree . use.
Table 1 Nickel-based alloys supplied to non-aerospace fields and their smelting processes
The components that serve under high temperature oxidation conditions include industrial gas turbine turbine discs and blades, steam turbine rotors, blades and bolts, flue gas turbine turbine discs and blades, as well as valves for internal combustion locomotives and diesel engines. In addition to oxidation resistance, nickel-based alloy materials for this type of use are also required to have high room temperature or high temperature tensile strength and plasticity, long lasting life or small creep elongation, and good fatigue resistance. . On the basis of determining the chemical composition, the high-temperature mechanical properties of nickel-based alloys depend on the purity of the material and the uniformity of the microstructure.
Parts used in corrosive media include steam generator heat transfer tubes, oil well pipes, oil well drilling and testing and protection pipes, submersible pump shafts, refining and chemical equipment, etc. In addition to certain strength requirements, nickel-based alloys for this type of use also pay special attention to the corrosion resistance of the material. On the basis of determining the chemical composition, inclusions and segregation phases (such as σ phase in nickel-based alloys) are the main causes of damage to the service life of nickel-based alloys in corrosive media.
