New technology and direction of diamond circular saw blades for cutting natural stone
At present, the development of diamond circular saw blades mainly has the following characteristics: (1) to produce high-efficiency and high-quality stone saw blades, and to develop special diamonds for saw blades; (2) to pay more attention to the research of powder, matrix and sintering process; (3) to pay more attention to Research on sawability and sawing mechanism of stone materials; (4) Development of laser welding saw blades; (5) Development of ultra-large diamond circular saw blades.
With the improvement of market demand, the application of diamond circular saw blades is becoming more and more extensive. The future development direction of diamond circular saw blades is to improve sawing efficiency, saw blade life, reduce production costs, and reduce noise and environmental protection. In order to achieve the above purpose, it is necessary to improve the material, structure and size. First of all, in terms of materials, various manufacturers pay more attention to the research of matrix and matrix formula, and strive to improve the life and efficiency of saw blade cutting stone on the basis of considering economy. Secondly, in terms of structure, the purpose of reducing noise and improving machining accuracy is achieved by changing the structure of the diamond circular saw blade. At present, the research and development of low-noise saw blades generally follow two approaches: one is to change the structure of the substrate, process specific grooves on the substrate, and fill the grooves with Yangni material; the other is to divide the substrate into three layers and combine them. The middle layer adopts damping material. Again, in terms of size, the diameter of diamond circular saw blades for cutting stone is getting larger and larger, and the ratio of thickness to diameter is getting smaller and smaller. The diameter of the largest diamond circular saw blade in the world has reached 5m. The best use effect is achieved by shaping, correcting, stressing, and heat treating the saw blade.
Application of pre-alloyed powder in diamond circular saw blade matrix material
Pre-alloyed powders are fairly uniform in composition because each powder particle contains the various metal elements that make up the alloy. Since the eutectic point is much lower than the melting point of the individual elements in the alloy, the sintering temperature required for the pre-alloyed powder is low. At present, most diamond tools such as diamond saw blades and core drills for stone cutting use a considerable proportion of pre-alloyed powder in the manufacturing process, and the application range of pre-alloyed powder is constantly expanding.
Advantages of using pre-alloyed powders in carcass materials
(1) Greatly improve the performance of diamond saw blades for cutting stone. Because the pre-alloyed powder is more evenly distributed than the mechanically mixed powder. The segregation of components is fundamentally avoided, so that the structure of the carcass is uniform and the performance tends to be consistent; the pre-alloyed powder is fully alloyed, so that the carcass has high hardness and high impact strength, which can greatly improve the compressive and bending strength of sintered products. Improve the holding force of the diamond, increase the sharpness of the diamond saw blade, and prolong the service life of the saw blade.
(2) Significantly reduce the cost of diamond saw blades. Since the pre-alloying greatly reduces the activation energy required for the diffusion of metal atoms during the sintering process, the sintering performance is good, the sintering temperature is low, and the sintering time is shortened. and power consumption. In the case of the same cutting performance, the use of pre-alloyed powder can reduce the diamond concentration by 15% to 20%, significantly reducing the cost of diamond saw blades.
(3) It is convenient for product quality control. Since the composition of each element of the pre-alloyed powder is fixed, the occurrence of various problems in the compounding process is fundamentally avoided, and conditions are provided for the stability of the product quality.
Preparation method and characteristics of pre-alloyed powder for diamond saw blade
At present, the common methods for preparing pre-alloyed powder mainly include the following.
The high-pressure atomization method of pre-alloyed powder is to pre-melt the metals of various components into alloys according to the designed carcass ratio before sintering, and then atomize the powder to obtain the carcass powder of the required particle size. The atomization method can be divided into water atomization and gas neutralization according to the atomization medium, and the gas neutralization port uses air, nitrogen or xenon and other gases. The gas-customized cooling rate is fast, the yield of powder grain and fine powder is high, and the cost is low. Water atomization is especially suitable for metals and alloys with higher melting points due to the higher viscosity of water than gas and its strong cooling ability. At present, the pre-alloyed powder of the saw blade for cutting stone is mostly prepared by the atomization method, and the pre-alloyed powder produced by this method has the advantages of low sintering temperature and high degree of alloying. The disadvantage is that the atomization method requires high equipment, it is not easy to adjust the composition of the carcass, and the powder has high oxygen content, high cost, and the powder is nearly spherical, which is not conducive to pressing and granulation.
The co-precipitation method is to add a precipitant and a surface modifier to a solution containing two or more metal ions, and by strengthening the process conditions, the various metal ions are precipitated almost simultaneously to obtain a precipitate with uniform composition. The method of finally obtaining the desired powder after the precipitate is processed by thermal decomposition, reduction, crushing, sieving, etc. Studies have shown that iron-based pre-alloyed powder can be prepared by precipitating oxalate mixture and decomposing the precipitate.
Co-precipitation is an important method for preparing composite powders containing two or more metal elements. Since the components of the chemical co-precipitation method can achieve uniform mixing between molecules in the solution in advance, the composition of the product is uniform and stable, and other parameters (such as particle size, particle shape, etc.) are also easy to control. The prepared powder has the advantages of fine particle size, narrow particle size distribution range, uniform composition distribution, high purity and good sintering activity.
The mechanical alloying method is also called high-energy ball milling, which is to load different metal powders or dispersion-strengthened powders into a high-energy ball mill, and perform long-term ball milling in a protective atmosphere according to a certain ratio of balls to material and ball size. Under the action of mechanical driving force, the powder undergoes repeated extrusion, cold welding and pulverization processes, so that different raw material powders can be tightly combined at the atomic level. If the raw materials contain hard particles such as metals or ceramics that are immiscible in solid state, The hard particles are uniformly dispersed in the softer metal particles to produce a composite powder.
A remarkable feature of the mechanical alloying method is that it can synthesize materials that usually require high temperature processing at low temperature, and can obtain materials such as amorphous alloys and supersaturated solid solutions that are difficult to obtain by conventional methods. However, the mechanical alloying method is easy to bring impurities into the powder during the ball milling process, which reduces the purity of the product, and the repeated extrusion causes a large internal stress inside the powder, which affects the compaction and sintering properties of the powder.
There are many other pre-alloyed powder preparation methods, such as vapor evaporation method, ultrasonic chemical method, amorphous crystallization method, microemulsion method, etc. With the deepening of research, new preparation methods are constantly emerging, but as an industrial preparation method for the purpose of application, it is not yet mature.