Preparation of niobium alloy ingot

Niobium alloy ingots usually adopt two methods: powder metallurgy and vacuum melting. The powder metallurgy preparation first uses the hydrogenation-dehydrogenation process to prepare the powder, and then the niobium powder and the added powder of other alloying elements are fully stirred uniformly, isostatic pressing is carried out, and the ingot is sintered at a high temperature in a sintering furnace. The vacuum smelting method is generally used to obtain sheet alloy ingots through a combination of vacuum electron beam smelting and vacuum consumable furnace smelting.

Firstly, niobium powder produced by powder metallurgy is the main processing raw material for niobium ingots. The niobium rods formed by isostatic pressing of the flake powder are sintered in a vacuum vertical furnace to form the initial electrode of the niobium ingot. Due to the high melting point of niobium, higher energy is required for melting, and vacuum arc furnaces are usually not used directly to smelt niobium ingots. Generally, electron beam melting furnaces are used to melt niobium alloy materials through high-speed electron beams. Generally, in order to obtain high-purity niobium alloy ingots, niobium bars and alloying element materials are welded into electrodes, and electron beam melting is performed twice or more to improve the purity of the niobium alloy ingots. During vacuum electron beam smelting, under high vapor pressure, impurities with melting points lower than carbon, such as aluminum, iron, titanium, manganese, barium, potassium, silicon and other elements, are easily evaporated when the melting temperature of niobium is 2470℃. The condenser of the electron beam melting furnace is cooled and collected; however, low vapor pressure elements such as tantalum, tungsten, and molybdenum can hardly be removed during the smelting of the vacuum electron beam melting furnace, and are usually hydrometallurgical in the previous process. Removal; the interstitial elements carbon, nitrogen, hydrogen, and oxygen will be released from them in the form of gases and be pumped away by the vacuum furnace; in addition, the oxygen in the niobium alloy can be volatilized from it in the form of NbO and NbO2, or it can be combined with the carbon of the niobium alloy Volatilize into CO. Therefore, reducing the oxygen content in the niobium alloy mainly uses NbO2 to deoxidize, and the carbon element in the niobium alloy is mainly removed by the excess oxygen in it, but when the carbon content is not reduced to the expected effect after a vacuum electron beam smelting, Vacuum electron beam melting should not be continued, but re-melting under vacuum and with higher nutrient conditions. In this process, the carbon content can continue to be reduced and the oxygen content may also be increased.

After electron beam melting and purification, the composition of the niobium alloy ingot is analyzed, the alloy element content is adjusted according to the analysis result, the alloy element with low melting point and volatile is added, and the vacuum consumable electric arc furnace smelting is easier. The uniform composition and high purity niobium alloy ingot is obtained.