How to choose cemented carbide production

       

How to choose cemented carbide production

In the first aspect, the average particle size and size of WC and compound carbides.

 

    Here we only talk about the particle size of the raw material, as for its chemical composition and other physical properties. First, we need to understand how the particle size of the powder is formed and how it affects the alloy. We know that the particle size of a powder is the particle size of the aggregate (group) of the atoms or molecules of the substance, which is controlled by the particle size of the raw materials and the processing technology. In terms of formation mechanism, what is useful to us and must be paid attention to is the particle size of the same material, which is related to the amount of internal energy and surface energy it contains. Therefore, powder metallurgy is particularly important for its particle size and particle uniformity. This is also one of the important reasons why my country's cemented carbide is not comparable to developed countries. Due to the wide range of particle size distribution of the same batch of raw materials, the energy contained between the agglomerates and the agglomerates is very inconsistent. In this way, under the same sintering temperature and system, the structure of the produced alloy is unbalanced and the grain is unstable, which makes the alloy use Performance is greatly reduced. Mainly manifested in the poor wear resistance of the alloy, easy to form crescent-shaped knife edge, unsatisfactory precision and so on.

 

    In the second aspect, the particle size of WC and compound carbide should match.

 

    On this point, Chinese alloy manufacturers pay little attention. Regardless of whether CK32 or CK40 or CK24 compound carbides (including Ta and Nb are used), and no matter what raw materials are used, they only consider the content of W, Ti, Ta, C, and Co in the alloy mixture. Less consideration is given to the particle size of compound carbides. Of course, it’s no wonder that since most of China’s duplex carbide production follows the crude production process of the former Soviet Union, it is difficult to control the particle size of the product in a true sense. Therefore, alloy manufacturers have no choice but to produce what they produce. What to use. We know that if the grain size of WC does not match the grain size of the compound carbide, it will seriously affect the quality of the alloy. If the compound carbide is too thick, it will easily form lumps and peel off. Excessive details are not enough to protect the WC base. Therefore, the choice of grain size compound carbide depends on its requirements for alloy grain size and product performance.

 

The third aspect is the solid solubility of compound carbides.

    The solid solubility of compound carbides is very important, and it is also the least noticeable. To clarify this issue, it is necessary to first explain the production process of compound carbide. As mentioned earlier, since the country basically uses the crude production process of the former Soviet Union, it is impossible to produce high-quality compound carbides from the process itself. Now take the production of CK32 compound carbide as an example to illustrate. Mix WC-87.5kg, TiO2-78kg, C-34.5kg, press the boat, and then sinter it in a 2,000-degree carbonization furnace. A batch of CK32 compound carbides was produced. Here, we must focus on the forming principle. First of all, TiO2 and C react sharply at high temperature. The simple equation is: TiO2 +3C=TiC+2CO↑. The generated TiC is very active. At this time, WC with a simple hexagonal crystal structure can quickly dissolve in TiC with a face-centered structure. But we know that dissolution is a very common phenomenon in nature. Except for liquids and gases that can be dissolved by convection, solids can only be dissolved by diffusion. In this way, the problem comes, because TiO2 and C can produce a large amount of CO gas at high temperature, so that in the formation of compound carbide, a large number of honeycombs will be produced in the finished product, so that WC will encounter in the process of diffusion and dissolution. Various unfavorable dissolution environments such as vacancy, dislocation and oversaturation. At present, the only way to alleviate this defect is to press the boat (or call it to hit the boat), the tighter and more uniform the better. Therefore, the production quality of a product is closely combined with human factors, not to mention that the craft itself has severe punishment defects!

 

    Because of this, we are required to be manufacturers of raw materials and alloys to devote themselves to researching new processes and continuously improving product quality.