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Niobium alloy preparation methods include ingot preparation, plastic processing, cutting, welding, heat treatment and coating.

Ingot preparation: mainly powder metallurgy method and smelting method.

The powder metallurgy method is suitable for the preparation of small niobium products and ingots for post-processing. Vacuum electron beam melting, vacuum waste arc melting, and the combination of these two melting methods are the main methods for preparing niobium and niobium alloy ingots. Electron beam melting is used for the purification of niobium and niobium alloys and the preparation of small diameter ingots. Consumable arc melting can produce ingots of larger size and more uniform alloy composition. Using electron beam suspension zone melting, high-purity niobium and niobium single crystal ingots can be prepared.

Compared with the smelting method, the powder metallurgy method has high cost and poor purification effect, and is generally rarely used. The smelting method can obtain ingots with high purity, uniform composition and properties. Electron beam melting is commonly used to produce pure niobium ingots. Niobium alloy ingots are generally produced using an electron beam-consumable electric arc furnace dual melting process, that is, hydrogenated-dehydrogenated niobium powder and alloy element powder are mixed to make electrodes, and then smelted in an electron beam furnace for purification. The alloy element content is analyzed and adjusted, and then it is smelted in a vacuum consumable electric arc furnace into an ingot with uniform composition. Volatile alloy elements (such as titanium, vanadium, aluminum, chromium, etc.) should be added during consumable arc melting.

Plastic processing: Pure niobium ingots can be forged, extruded, rolled and drawn at room temperature to 500°C. Niobium alloy has high strength, so it is generally necessary to perform preliminary processing such as extrusion and forging above 1200°C, and then extrusion, forging, rolling and other methods below 500°C to produce bars, plates, strips, and foils. , pipes, wires and special-shaped materials and other products.

The niobium alloy ingots produced by the smelting method have coarse grains and need to be crushed by extrusion before they can be processed into finished products. In order to fully break the coarse as-cast grains, the extrusion ratio is generally not less than 4. At high temperatures, interstitial elements oxygen, nitrogen and hydrogen, especially oxygen, react easily with niobium alloys. After the alloy is oxidized, not only does loose oxide scale form on the surface, but oxygen can penetrate into the alloy matrix to form a hard penetration layer, making plastic processing difficult. Therefore, niobium alloys must take measures such as metal cladding, coating or inert gas protective heating during extrusion blanking and other thermal processing. Niobium alloys, especially pure niobium, tend to bond with the mold during the stretching process, so they must be anodized first to form a dense oxide film on the surface of the workpiece and use lubricant. Cutting: Niobium and niobium alloys are prone to wear and sticking to the cutting tools during cutting. Therefore, it is advisable to use organic solvents such as oil-water emulsion and carbon tetrachloride to cool and lubricate while cutting, while keeping the tool tip sharp. When cutting niobium and some niobium alloys, the workpiece can easily bond with the tool and cause surface oxidation. Low-speed cutting should be used and coolant should be used for cooling.

Welding: Vacuum electron beam welding and inert gas shielded tungsten arc welding can be used, and brazing can also be used to weld titanium and titanium alloys. Compared with tungsten and molybdenum alloys, niobium alloys, especially low-strength and medium-strength niobium alloys, have excellent welding properties. Commonly used welding methods include electron beam welding and tungsten electrode inert gas shielded welding. Alloys such as Nb-10Hf-0.7Zr-1Ti, which are less sensitive to interstitial element contamination, can be shielded and welded with inert gas outside the welding box. Niobium alloy weldments often need to be annealed to eliminate stress and improve the plasticity of the weldment.

Heat treatment: There are two main types of heat treatment: annealing and solution aging. To prevent atmospheric pollution, heat treatment must be carried out under vacuum or high-purity inert gas protection. The heat treatment of niobium alloy should be carried out under a vacuum of 10-4 to 10-5 Torr. Heat treatment is mainly recrystallization and stress relief annealing, and some alloys also use homogenization annealing, solid solution and aging treatment. The surface of the workpiece must be strictly cleaned before heat treatment to ensure the quality of the workpiece.

Coating: When used in high-temperature oxidizing environments, an anti-oxidation coating must be added.