The preparation of ingot billet mainly includes powder metallurgy and melting.

Powder metallurgy is suitable for the preparation of small niobium products and ingot for post-processing.

Vacuum electron beam melting, true blank arc melting and their combination are the main methods to prepare niobium and niobium alloy ingot.

Electron beam melting is used for purification of niobium and niobium alloys and preparation of small diameter ingot billet.

Consumable arc melting can produce large - size ingot and more uniform alloy composition.

High purity niobium and niobium single crystal ingot can be prepared by electron beam suspension melting.

Compared with melting process, powder metallurgy process has high cost and poor purification effect, so it is rarely used.

The ingot with high purity, uniform composition and performance can be obtained by melting.

Electron beam melting is commonly used to prepare pure niobium ingot.

Generally, the production of niobium alloy ingot is made by electron beam-consumable arc furnace double melting process, that is, the electrode is made by mixing hydrogenated and dehydrogenated niobium powder with alloying element powder, which is purified in electron beam furnace, and the alloying element content is analyzed and adjusted, and then the ingot with uniform composition is melted in vacuum consumable arc furnace.

Volatile alloying elements (such as titanium, vanadium, aluminum, chromium, etc.) should be added during consumable arc melting.

Plastic processing pure niobium ingot billet can be forged, extruded, rolled and drawn in the range of room temperature ~ 500℃. The strength of niobium alloy is high, so it is generally above 1200℃ for extrusion and forging and other preliminary processing, and then below 500℃ for extrusion, forging, rolling and other methods to produce bar, sheet, strip, foil, tube, wire and profile products.

The grain of niobium alloy ingot obtained by smelting is coarse, which can only be processed after being crushed by extrusion.

In order to fully break the coarse as-cast grains, the extrusion ratio is generally not less than 4.

At high temperature, the interstitial elements oxygen, nitrogen and hydrogen, especially oxygen, easily react with niobium alloy.

After the oxidation of the alloy, not only the surface of the loose oxide skin, but also the oxygen can penetrate into the alloy matrix to form a hard penetrating layer, which makes the plastic processing difficult.

Therefore, some measures such as metal cladding, coating or inert gas protection heating must be taken during extrusion and other hot working processes.

Niobium alloy, especially pure niobium, is easy to bond with the mold during the tensile process, so it is necessary to anodize the workpiece first, so that the surface of the dense oxide film and the use of lubricants.

Cutting niobium and niobium alloy cutting is easy to wear and bond the cutting tool, so the cutting time to use oil-water emulsion, carbon tetrachloride and other organic solvents cooling and lubrication, while keeping the sharp tip.

Niobium and some niobium alloys in the cutting process, the workpiece is easy to bond with the tool and surface oxidation, should be used in low speed cutting and cooling liquid cooling.

The welding can be done by vacuum electron beam welding, inert gas shielded tungsten arc welding, or brazing with titanium and titanium alloys.

Compared with tungsten and molybdenum alloys, Niobium alloys, especially low and medium strength niobium alloys, have excellent welding properties.

The common welding methods include electron beam welding and tungsten inert gas welding.

The alloys such as Nb-10Hf-0.7Zr-1Ti, which are not so sensitive to the pollution of gap elements, can be welded with inert gas outside the welding box.

Niobium alloy welds are often annealed to eliminate stress and improve plasticity.

There are two kinds of heat treatment: annealing and solution aging.

In order to prevent air pollution, heat treatment must be carried out under the protection of vacuum or high purity inert gas.

The heat treatment of niobium alloy should be carried out in 10-4 ~ 10-5 supporting vacuum. The heat treatment is mainly recrystallization and stress relief annealing, some alloys also use homogenization annealing, solution and aging treatment.

Before heat treatment, the workpiece surface must be cleaned strictly to ensure the quality of the workpiece.

When the coating is used in high temperature oxidation environment, anti-oxidation coating must be added.