Application of advanced cemented carbide technology in the manufacture of large-scale top hammer

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With the development of the superhard material industry, the top hammer material has maintained the material of 8% Co with medium and fine grains for a considerable period of time, and an important factor supporting the continuous improvement of the service life of the top hammer is the new process technology of cemented carbide. Results applied to top hammer manufacturing. Top hammer manufacturers have successively introduced cold isostatic pressing technology, new wet grinding process and pressing process, and adopted advanced cemented carbide technologies such as low-pressure sintering. Great improvement.

At present, the large-scale six-sided top hammer has dominated the Chinese superhard material composite cavity market, and the fine and sub-micron carbide has also become an important direction for the development of new top hammer materials. Its compressive strength and bending strength are At the same time, with the introduction of advanced cemented carbide technology into the production process of the new material top hammer, the practical application effect of the new material top hammer has reached a very high level, and the hammer consumption of diamond production has been controlled at <1kg/10,000 carats , the best effect is 0.15 ~ 0.3kg / 10,000 carats.

This paper summarizes the application of advanced cemented carbide technology in large-scale top hammer products, especially the high-performance guarantee technology for fine-grained and sub-fine grained cemented carbide, and focuses on its development trend.

In the process flow of cemented carbide production, compound preparation, pressing and sintering are the three main processes. Tiltable rolling ball mill, stirring ball mill, spray drying. The complete set of advanced cemented carbide technologies such as cold isostatic pressing, low pressure sintering, and dewaxing and sintering integration have been maturely applied to high-performance, high-precision, small-sized products such as CNC blades, ball teeth, and bars. The preparation of solid alloy top hammer has not been systematically applied. In order to achieve our goal, according to the technical status of the fine-grained and sub-fine-grained top hammers, and the experience in the application of CNC inserts, ball teeth, and bar production technology systems, the whole system of advanced cemented carbide manufacturing technology is introduced into the big top. It is very necessary in the production of hammers. The process flow is shown in Fig.

In this technical system, especially the advanced technology of mixing spray drying and dewaxing and sintering integrated into low pressure sintering, the production process of large top hammers can be upgraded in quality, the overall control level has been greatly improved, the process flow has been shortened, and artificial influence has been achieved. The factors are reduced, the production environment is greatly improved, the resource and energy consumption is reduced, and it is more suitable for the quality process control of fine products and sub-fine grain top hammers.

Mixture spray drying
The quality of the alloy depends to a large extent on the quality of the mixture. Wet grinding + mechanical granulation production process, the equipment is simple, but the process is long, the drying and granulation need to be completed in two separate processes, the material is easy to oxidize and dirty, and the production automation level is low, the output is low, and the mixed Material quality is poor.

The wet grinding + spray drying production process requires large investment and complex equipment, but the production automation level is high. The entire drying process is carried out in a closed state, and the oxygen content of the closed equipment can be monitored in real time to ensure that the oxygen content of the mixture is within the allowable range. Within the range, the produced mixture has good flow performance, stable bulk density, uniform particle size distribution, and large output, which can meet the needs of high-quality, high-performance, and large-scale cemented carbide production. Although the wet grinding + spray drying production process is applied to CNC blades, ball teeth, bars, rolls and other products, and has achieved good results, it is applied to the large-volume solid body of the top hammer, and it is also a fine-grained material. The compression performance of the material must be fully guaranteed.

Control of Mixture Particle Size and Composition
Using the control method of the spray drying process to control parameters such as slurry viscosity, nozzle size, spray temperature and pressure, the bulk density and particle size composition of the top hammer mixture can meet the top hammer pressing requirements, and each batch of materials and batches can be achieved. The basic uniformity between them enables the compressibility of the mixture to be quantitatively and stably controlled.

Press forming
Isostatic pressing is the best way to prepare large-sized compacts. It can effectively reduce the internal pores of the compact, make the sintered alloy structure dense and uniform, and improve the fracture strength and service life of the alloy. The process of molding + cold isostatic pressing repressing is used to press large-sized top hammers, which has a good effect on improving the density and uniformity of the green compact and eliminating the internal defects of the top hammers. After the spray material is used, the tap density of different batches of mixtures with stable, uniform and good fluidity can be basically kept unchanged, which provides a good solution for direct cold isostatic pressing of the mixture, improving the dimensional control accuracy of the compact and reducing the processing amount. conditions for the promotion of industrialization.

Integrated dewaxing sintering – low pressure sintering process
Vacuum – hot isostatic pressing sintering has been popularized in top hammer production. At present, the most advanced air pressure sintering furnace in cemented carbide production integrates the functions of removing forming agent, sintering, and hot isostatic pressing of cemented carbide. The sintering equipment that is completed in one production process is very suitable for the sintering of low-junction fine-grained cemented carbide with very strict carbon content control requirements. In the production of ultra-fine bars, this type of sintering furnace is mostly used, while the pressure sintering furnaces used by other manufacturers in the industry to produce top hammers generally do not have a dewaxing function. Some manufacturers take the method of first dewaxing in a bell jar furnace and then transferring it to a pressure sintering furnace for pressure sintering. Due to the low dewaxing and pre-sintering temperature, the strength of the semi-finished product is poor, and the large top hammer is not easy to handle. Timely sintering is very easy to increase oxygen, which is not conducive to the control of carbon content of the fine-grain top hammer, and even causes decarburization; some manufacturers first use a multi-atmosphere vacuum sintering furnace to dewax the top hammer, vacuum sintering, and then use a pressure sintering furnace. pressure sintering method. Although pressure sintering is used in the end, relatively speaking, the process of removing molding agent, sintering, and hot isostatic pressing is completed at one time, with short process, high efficiency, less human factors, more stable carbon content control, and more uniform structure.

With the application of advanced cemented carbide technology, the service life of large-sized top hammers has reached a very high level, meeting the current needs of the diamond industry. Under the premise of the rapid development of the superhard material industry, the continuous development of synthetic large cavities and the “exploitation” of existing cavities have proposed higher stability of the material and quality of the fine-grained and large-sized top hammers. Requirements, the systematic application of advanced cemented carbide technology is the development trend to ensure the quality of the top hammer.

Equipment selection: The RVS vacuum sintering furnace provided by SIMUWU is an excellent product for processing this kind of process. It has the characteristics of good temperature uniformity and high temperature control accuracy. SIMUWU provides a professional team of engineers who can solve various problems encountered in the production process and are committed to giving customers the most convenient and efficient experience.