Advantages of non-hydrocarbonization of rare metals and compound carbides

       As a strong reducing agent, hydrogen (H2) is widely used in the reduction of rare metal oxides and as a protective gas in high temperature furnaces. However, in the production of tungsten carbide (WC) and the production of compound carbides of tungsten (W), titanium (Ti), tantalum (Ta), and niobium (Nb) (including other carbides produced from metal oxides), H2 The effect is not exactly the same. In the production process of WC, H2, as a carrier and protective gas, both participates in the reaction and plays a protective role. First, H2 reacts with C to generate a series of organic gases such as CH4. The organic gas reacts with W to generate WC, and at the same time replaces H2. The WC produced in this way has the advantages of complete lattice, complete carbonization and loose texture compared with the WC made by non-hydrogen passing.

    However, according to the traditional process, passing hydrogen in the production process of W, Ti, Ta, Nb and other compound carbides not only has no benefits, but will bring a series of drawbacks.

    First, due to the high temperature of this type of carbide, H2 can react with the furnace tube and boat (which has no effect on the reaction with carbon black in the raw material), which will shorten the service life of the furnace tube and boat. .

    Second, the source of Ti required for the production of traditional compound carbides is TiO2. The removal of oxygen in TiO2 mainly depends on the carbon black prepared in the raw material, and some of it also reacts with H2 in the state of hydrogen flow. As a result, the actual carbon distribution is far from the theoretical carbon distribution. And due to the change of H2 flow and the change of the required carbonization temperature, the total carbon of the duplex carbide fluctuates greatly.

    Third, because the carbides of Ti, Ta, and Nb can dissolve their own elemental metals, and these three metals can easily react with H2 to form hydrides. Among them, titanium metal is especially metal, which absorbs a large amount of hydrogen at about 500 ° C, so titanium carbide in the cooling process by hydrogen carbonization can easily generate titanium hydride. The hydrogen desorption temperature of titanium hydride is around 1300 ° C, which is the temperature region where the liquid phase of the cemented carbide is formed, which undoubtedly has a great influence on the quality of the cemented carbide.

    In addition, the traditional process of compound carbide production can generate a large amount of CO gas, which is not only a good protective gas, but also makes the material loose, so hydrogen carbonization is meaningless. Because of this, the non-hydrogen carbonization of duplex carbides is also one of the important guarantees for the excellent quality of our company's products.