Advantages of non-hydrocarbonization of rare metal compound carbides

       As a strong reducing agent, hydrogen (H2) is widely used in the reduction of rare metal oxides and protective gas in high-temperature furnaces. However, in the production of tungsten carbide (WC) and tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb) compound carbides (including other metal oxides to produce carbides), H2 The effect is not exactly the same. In the WC production process, H2 as a carrier and protective gas participates in the reaction and plays a protective role. First, H2 reacts with C to produce a series of organic gases such as CH4, and then the organic gas reacts with W to produce WC, and at the same time replace H2. The WC made in this way has the advantages of complete crystal lattice, complete carbonization, and loose texture compared to WC made without hydrogen.

    However, in the production process of W, Ti, Ta, Nb and other compound carbides according to the traditional technology, hydrogen is not only not beneficial, but will bring a series of disadvantages.

    First, due to the high temperature at which this type of carbide is produced, H2 can react with furnace tubes and boats (with no effect on the carbon black in the raw materials), which will shorten the service life of the furnace tubes and boats. .

    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 blended in the raw materials, and part of it also reacts with H2 in the state of hydrogen flow. As a result, the actual amount of carbon allocated is far from the theoretical amount of carbon allocated. And due to the change of H2 flow rate and the change of the required carbonization temperature, the total carbon of the compound carbide fluctuates greatly.

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

    Furthermore, a large amount of CO gas can be produced during the production of compound carbides in the traditional technology. This gas is a good protective gas and can loosen the texture of the material. Therefore, hydrogenation carbonization is meaningless. For this reason, the non-hydrocarbonization of compound carbides is also one of the important guarantees for the excellent quality of our company's products.