The hot pressing process of the saw blade for cutting ceramic tiles
The sintering of the diamond segments for cutting ceramic tiles generally uses a combined graphite mold. The hot-pressing sintering of the diamond segments is to use the graphite mold itself as an electro-positive element to pass a large current to both ends of the graphite mold, and at the same time press the mold resistance and the resistance of the diamond segments to heat up the hot-pressed powder, which is an internal heat type. . The heating rate is fast, the temperature of each part of the mold cavity is relatively uniform, and the actual temperature in the mold is much higher than the surface temperature of the mold measured by infrared rays, and the difference is initially estimated to be about 100~120℃. Under normal circumstances, there are three main reasons for the scrapping of graphite molds: (1) the carbon powder falls off after the surface is oxidized and the size changes and is scrapped; (2) knocking damage when disassembling the mold; (3) serious adhesion due to the loss of liquid phase of the diamond segments, Damage the indenter or the surface of the partition when removing the diamond segments for cutting ceramic tiles or cleaning metal oxide deposits. In order to avoid man-made damage to the mold, the force when disassembling and assembling the mold should be light, and try not to hit the mold with hard objects. Generally, a rubber hammer is used to hit the indenter. In order to improve the heating efficiency and service life of graphite molds, graphite materials with good degree of graphitization, high resistivity, and high purity, density and strength should be selected. The higher the density, the lower the porosity, the less impurity content, and the better the oxidation resistance; the graphite mold is not dense enough, and the sintered liquid phase is easy to fill the voids, resulting in damage to the mold and the diamond segments adhesion and demoulding; so the graphite density is average It is required to be above 18g/cm. The graphite strength requires that the compressive strength is greater than 30MPa when heated to a temperature of 800~1000℃.
Influence of impurities on ceramic tile cutting saw blades
Since the diamond segmentss of various ceramic tile circular saw blades are relatively strict in distinguishing the diamond particle size, once the coarse particles are doped in the diamond segments, the quality of the diamond saw blade is fatal, especially the fine hob and cylindrical wheel, which often cause The whole polishing line is shut down due to the problem of knife marks. Therefore, special attention should be paid to the cleanliness of the working surface and the storage of materials during the weighing and moulding process of the hot pressing process. Do not work at the same time as other particle sizes.
The sintering temperature is the most important parameter of the hot pressing process. If the sintering temperature is too low, the density and alloying degree of the carcass is insufficient, and the mechanical properties such as hardness and strength are lower than the formula design standards, which will have fatal effects on the quality of the tool. influences. However, if the temperature is too high, the liquid phase will be lost too much, the formula performance will change, and the density will decrease, which will also affect the quality of use. The proper temperature is usually obtained by optimizing the design through experiments, but after many experiments, it has been proved that the lowest temperature when the diamond segments of the diamond saw blade can be pressed to the design size is the optimal sintering temperature. If it is limited pressing, the indenter is just flattened. temperature. The optimum temperature allowable fluctuation range should not be less than ±10°C, and the liquid loss of the diamond segments is 2%~6% within this temperature range. Therefore, to obtain stable carcass performance, on the one hand, process control is very important, and on the other hand, the process stability of the formula is also critical. As far as the current temperature control level of domestic equipment is concerned, the formula that maintains the basic stability of the carcass performance within the fluctuation range of 10~20 °C can ensure the stable quality of mass production and is a formula with process stability.
Recipe for diamond ceramic tile cutting blades
Most of the ceramic tile cutting saw blades use iron-nickel (cobalt)-bronze-based formula, the sintering temperature is 750~860℃, most of the Cu-Sn is in liquid phase in the final temperature holding stage, and all Ni and a small amount of Fe (below 8%) are dissolved in Cu -Sn liquid phase completes alloying very quickly, and liquid phase fills pores rapidly through flow to achieve densification. It belongs to the typical liquid phase hot pressing sintering process, so the sintering process can be completed in a very short time, generally the final temperature holding time is 2~3min. The design of the pressure is based on the liquid content, and the general design pressure is 18~25MPa. After sintering, the pressure relief should not be too fast, otherwise the molten matrix will release the external force in an instant, and the internal stress generated by cooling will cause its shape to change or crack, and the internal stress of the matrix to the diamond will also be reduced. The pressure relief temperature should be 150°C lower than the sintering temperature. In the production process, the pressure relief temperature is often neglected and the quality of the diamond segments is degraded.
Pressing and sintering process of continuous ceramic tile cutting saw blades
Integral sintered ceramic tile saw blades are cold-pressed before hot-pressing. The main purpose of forming is to facilitate hot-pressing, reduce the thickness of the mold, and increase the number of single pressings. The cutter teeth are generally continuous and directly cold-pressed on the substrate. In order to increase the bonding strength between the carcass and the substrate, the joint part between the substrate and the carcass is processed into a groove type. The mold sleeve, core mold and indenter of the cold-pressing mold are made of GCr15, T10 or 9CrSi and other heat treatment hardness of 52~55HRC, and the rest of the mold release sleeve, gasket and pressure pad are made of No. 45 steel, and the press adopts a 300T four-column press.
Hot-pressing sintering is carried out in a bell-type hot-pressing machine, protected by a hydrogen atmosphere. The mold is generally made of stone black mold, and a d300 edging wheel can press about 13 pieces in one furnace. The bell furnace hot press is different from the diamond segments hot press. It is heated by the nickel-chromium resistance wire on the outer wall of the inner cover. Moreover, due to the large sintering volume, the temperature homogenization of the workpiece is completely dependent on thermal radiation, convection and self-heat transfer, so the final temperature holding stage is required to require a temperature equalization process, so the general holding time is about 30~45min. The principle of temperature determination is the same as The hot pressing of diamond saw blades for cutting ceramic tiles is similar, and the pressure is slightly lower than that of ceramic tile saw blades, generally 15~18MPa. The height of the matrix of the qualified sintered diamond circular saw blade should be the same as the design height, the hardness should meet the design requirements, and the percussion matrix is crisp and pleasant, not stuffy.
In fact, the diamond segments of the welded ceramic tile saw blade is made into a fan type, which is spliced in place during welding, which can fully achieve the appearance and use effect of the continuous ceramic tile saw blade. The only advantage of integral sintering is that the sharpness of the formula of the ceramic tile saw blade can reach the highest level, without considering the problem of the decrease in welding strength caused by the weakening of the matrix strength, but the process is cumbersome, the production cycle is long, and the manufacturing cost is high; It is thick and cannot be reused, and the cost of raw materials is high; the process control is difficult and the quality stability is poor. Therefore, unless special occasions or products are required, the monolithic sintering process is generally used to produce ceramic cutting saw blades.