Hydrogen (H2) as a strong reducing agent, is widely used in the reduction of rare metal oxide protective gas and high-temperature furnace. However, tungsten carbide (WC), and tungsten (W), titanium (Ti), tantalum (Ta), niobium (Nb) carbide production duplex, H2 role is not exactly the same. In the WC production process, H2 gas as a carrier and both participate in the reaction and the protection plays a protective role.First,H2 and C reaction CH4 and a series of organic gases,organic gases then react with W generated WC, while the replacement of H2.Such production WC than non-hydrogen-WC with advantages of a complete lattice, completely carbonized, loose texture and so on.
However, according to the traditional process through hydrogen production process W, Ti, Ta, Nb, etc. duplex carbides, not only no benefit, but will bring a series of drawbacks.
First, Due to the temperature of the compound carbide production is very high, H2 with the furnace tube, boat (with no effect in the raw material of Carbon black reaction) and other reaction, which would make the furnace tube and shorten the life of the boat.
Second, since the source of the required conventional duplex Ti carbide production are TiO2. TiO2 removed oxygen mainly by raw material and carbon black, also in a portion of the hydrogen-state reaction of H2. This resulted in the actual carbon content and carbon content falls far short of the theoretical. And because of carbonization temperature changes and required changes in H2 flow caused by fluctuations of total carbon and volatile.
Third, since H2 react with oxygen in TiO2, Ta2O5, Nb2O5, etc. In production process, so that in the production of carbon black is much lower than with the non through hydrogen with carbon black.This resulted in a reduced C concentration in the material, and thus easier to N2 in the air in contact with Ti, Ta, Nb and react. Therefore, the amount nitrogen content of Compound carbides hydrogen is higher than non-through hydrogen high (compound carbides nitrogen can cause brittle).
Fourth, as Ti, Ta, Nb carbides can dissolve the elemental metal itself, and the three metal is easy to react with hydride to generate hydride. One in particular, titanium metal absorb a large number of the hydrogen around 500 ℃, therefore titanium carbide of hydrogen-carbonizing in the cooling process is very easy to generate titanium hydride. The titanium hydride hydrogen desorption temperature is at about 1300 ℃, which is the carbide phase formation and crystallization temperature region, there is no doubt have a significant impact on the carbide quality.
Furthermore, the compound carbides production process in the traditional process itself can produce large amounts of CO gas that is both well protected gas, but also make the texture of loose material, so also through hydrogen carbide seem meaningless. For this reason, Compound carbide non-through hydrogen carbide is my company （Changsha Langfeng Metallic Material Co.,Ltd ) one of the product quality important guarantee.
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