New technology brings a leap in cermet carbide

       The world is developing and the industry is progressing. In the past, the quality and variety of traditional cemented carbide could not meet the needs of development. Especially in recent years, the rapid development of cemented carbide production technology has posed a huge challenge to the backward productivity in the past. At present, the products with high technical content and promising development prospects in the field of cemented carbide include nano- and ultra-fine cemented carbide, CNC inserts and cermet alloy inserts. To this end, our company has produced high-quality and low-cost titanium nitride carbide through the transformation of equipment and process improvement and innovation, and has obtained national patents. Thus, it has laid a good foundation for the cermet cemented carbide manufacturing company to produce high-quality and low-cost alloy products.



1. The technical principle of the project



    The key technology for improving the preparation of titanium nitride carbide (TiCN) is that the company relies on its own patented technology and independently develops and develops a high-quality, low-cost TiCN production process on the basis of the original production process. The key point of this technology is the step-by-step production of the original process, which can be completed in one step by adjusting the formula and temperature, which greatly reduces energy consumption, saves manpower and increases production capacity. At the same time, the product quality has also been greatly improved, overcoming the long-term situation of high oxygen and low nitrogen in TiCN, and filling the technical gap in this field for China.



    Basic working principle:



    At present, as one of the most promising categories of cemented carbide, cermet cemented carbide has been developing rapidly and has a very broad prospect. However, the low quality and high price of TiCN, the main raw material of the alloy, has become a stumbling block for the development of cermet carbide in my country. Therefore, it is urgent to develop high-quality and low-cost TiCN as soon as possible.



    1. The quality requirements of cermet carbide for TiCN:



    ① Low oxygen content. Oxygen exists as an impurity phase in the alloy, and oxygen (O), nitrogen (N), and carbon (C) form an interstitial solid solution with titanium. However, high oxygen content will result in high porosity and poor compactness of the alloy. Therefore, as the quality standard of TiCN, the first thing to do is to reduce the oxygen content.



    ②. The nitrogen content must reach a certain content. Although titanium can burn in nitrogen at high temperature, its reaction speed is relatively slow, which causes the nitrogen content of TiCN to often fail to meet the standard.



    ③ The solid solubility of TiC and TiN is high. Because the binder phase in the alloy can only wet TiC, the effect of TiN in the alloy is through the solid solution with TiC. Otherwise, it will not only fail to play the role of TiN, but will make the alloy more brittle.



    ④. The particle size should be uniform.



    2. Preparation process commonly used in domestic traditional TiCN



    ①Completely mix 80kg of titanium dioxide (TiO2) and 30.8kg of carbon black, press the boat and put it into a carbon tube furnace at about 2300℃ to sinter to produce TiC.



    ② Take 45kg of TiC produced above, add 60kg of TiO2 and 18kg of carbon black to mix the boat, and then carry out reduction and nitridation in a carbon tube furnace fed with N2. In order to reduce the oxygen in TiO2 as much as possible and make Ti fully nitrided, the sintering time of each boat was 4 hours and the temperature was 1800°C.



    In addition, TiCN is also produced by a method in which TiC and TiN are directly dissolved. Because the quality of the products produced by this method is not stable and the cost is very high, it is generally rarely used.



    3. Disadvantages of traditional methods



    ①. Since all the oxygen of TiO2 is reduced by C and it is best to achieve exactly all reduction. Otherwise, either the oxygen cannot be completely reduced, so that the oxygen content of the product is too high and cannot be used, or the content of the raw material C is too high, which affects the dissolution of N. Therefore, the TiCN produced by this method always has the phenomenon that O and C are too high and N is too low.



    ②. Since the compounded TiC hinders the combination of TiO2 and C to a certain extent, this method cannot always reduce the oxygen in TiO2 to a very low level. In addition, since the added TiC is relatively stable, it is not easy to be nitrided, so the Ti to form TiN basically depends on the reduction process of TiO2, which results in low nitridation efficiency.



    ③. Repeated production increases the cost of raw materials, especially the waste of N2 and the loss of electric energy.



    ④. The equipment utilization rate is low, and the production capacity cannot go up.



    4. The basic principle of our company's innovative process



    Since the requirements of TiCN are mainly for O to be low, and C and N to be controlled within a certain range, therefore, if a stable formula, stable sintering temperature, temperature time, and stable N2 and CO pressure can be controlled, then it can be produced. out the products we need. Through the long-term exploration and experiments of our company's scientific researchers, we finally found this path.



    ①Recipe: more traditional method: we mix TiO2 and C at one time (no TiC is required). In addition to completely reducing the O in TiO2, the added C needs to be in excess, so that the excess C and part of Ti form TiC, and the other part of Ti forms TiN.



    ②In the process, the temperature of one furnace and two levels is adopted and the temperature is automatically controlled. The primary temperature control is 1230°C, plus or minus 10°C. The main function of this temperature zone is to convert high-valent O in TiO2 into low-valent O, the equation is TiO2+C=TiO+CO↑, the purpose is to reduce part of O, activate the activity of TiO2, and further reduce and reduce the temperature in the high temperature zone. Carbonization and nitriding lay the foundation. It should be noted that the temperature control of this stage is relatively strict. We have conducted more than 30 experiments to find the stable reaction temperature zone. When the temperature is low, TiO2 will not react completely, and the generated gas contains a mixture of CO and CO2. Therefore, the amount of carbon taken away by the exhaust gas will not be stable, and the final product C content fluctuates greatly and becomes an unqualified product. If the temperature is too high, there will be some TiO2, and TiC will be formed prematurely, which is not conducive to nitriding in the high temperature area, resulting in insufficient N content of the product and coarse grains. The secondary temperature control is 1650°C, plus or minus 20°C. This stage is mainly for the complete reduction, carbonization and nitridation of TiO2. The main principle of this stage is that TiO rapidly reacts with C to form highly active metal Ti. Since the generated CO is continuously taken away, the excess C mainly ensures the reduction of O first. Therefore, the reduction of O is also relatively thorough. The O content in the final formed TiCN is very low (the minimum can reach 0.1%, which is more than five times lower than the O content produced by the traditional method). In addition, since the whole raw material starts from TiO2 to TiO and then to Ti, it is always in N2 It is equivalent to multiplying the nitriding probability of the raw materials, so the overall production time is only 2 hours/boat, which is half of the traditional method. And the temperature can also be reduced by about 150 ℃. The schematic diagram of sintering is as follows: