Alumina piezo ceramics are often formed by hot sintering. Since sintering usually causes deformation and shrinkage, it is generally required. To ensure the dimensional accuracy and shape accuracy of the workpiece. However, due to the general elasticity of alumina piezo ceramics materials.The modulus of elasticity is quite large, the brittleness is high, the hardness is high, and the crack sensitivity is strong, so the machining difficulty is mainly reflected in the processing hardness and processing brittleness. On the one hand, most of the piezo crystal forms are covalently formed by aluminum ions and oxygen ions.so the bonding energy between atoms is very high and has strong directionality, which is specifically represented by plastic deformation.Small, brittle material is easy to crack; its hardness is equivalent to the hardness of carbide , higher than the hardness of steel Several times, usually the high purity alumina piezo ceramic has a density of up to 3980 kg/m, a tensile strength of 260 MPa ,compressive strength of 2930 MPa and an elastic modulus of between 350 and 400 GPa is especially a hardness of 95 HRA. On the other hand, in general, the microstructure of alumina piezo ceramics is equiaxed grains, which is a polycrystalline structure composed of covalent bonds or ionic bonds, so it is specifically characterized by low toughness and external load under the stress, the piezo ceramic surface will produce fine cracks, and the crack will expand rapidly and then brittle fracture will occur.Therefore, the specific performance is that the fracture toughness is low. Under the action of external load, the stress will cause the piezoelectric material piezoceramic cylinder surface to be produced.Subtle cracks occur, and the cracks expand rapidly and brittle fracture occurs. Therefore in the alumina piezo ceramic is cutting in the process, there is often a phenomenon of collapse, that is, a small gap that cracks is on the surface of the piezo ceramics. When the cutting tensile stress is larger,At the same time, the resulting collapse will become more serious, which may result in the entire workpiece.
The alumina piezoelectric ceramic material substrates studied in this subject has the characteristics of high hardness, large brittleness, it is conventional size about 50mm X 50mm, blank thickness of about 1 mm, and finally requires the finished piezo ceramic substrate surface roughness. It is 0.01 m. During the grinding process, if the abrasive process parameters are unreasonable, such as abrasive type, abrasive grain size, and grinding pressure, the selection of the surface of substrates may be uneven, resulting in scratches. Scratches can cause the surface roughness of the workpiece to increase, and micro-crack damage can occur on the subsurface of the workpiece, which causes damage to the substrate during subsequent processing. In the severe cases, the substrate may be broken. At the same time, due to the existence of holes in the surface of the sintered piezo ceramic substrates, and there may be some large sized crystal grains, the unreasonable grinding process is likely to cause defects such as grain extraction embedding of the abrasive grains and the surface quality of the substrate. Reducing these defects can be eliminated in the subsequent fine grinding or polishing processes, which can take a long time and effort, or even remove them.
Alumina Pzt material piezoceramic tube transducer substrate is one of the most commonly used electronic ceramic substrates, in order to meet its technical needs in the industrial field.At the request, domestic and foreign scholars have done a lot of in the depth research in their mechanical processing. The grinding characteristics of the precision piezo ceramics were analyzed by a statistical design test method, and the optimal combination of process variables was determined to achieve the maximum improvement of the roughness of the alumina piezo ceramic surface. Synthetic diamond abrasives with different particle sizes were used to grind the ultrasonic wired ceramic disc produce under the different pressing pressures. It was found that the main PZT material removal mechanism in the coarse grinding stage was the extraction of grains on the surface of the piezo material and the micro-grain between the grains.
The crushing and fine grinding stage is due to the plastic flow on the surface of the piezoceramic tube piezoelectric transducer material which improves the surface quality. Through the discrete and fixed abrasive grinding test of alumina piezo ceramic substrates, the accuracy of the piezo ceramic substrate was analyzed by the grinding method, abrasive particle size, concentration and bonding agent type, grinding pressure, grinding disk rotation speed and grinding time. The influence of surface roughness and grinding efficiency, the analysis shows that the abrasive grain size has the greatest influence on the surface roughness and the grinding amount. It is better to use the abrasive bronze bond and the grinding disc made of copper and the surface is made. Trapezoidal thread groove, abrasive concentration, grinding disk speed, grinding pressure, grinding time also have a certain influence on the surface of roughness and grinding amount. It needs to be determined according to different surface roughness requirements and accuracy requirements.
Hubei Hannas Tech Co.,Ltd is a professional piezoelectric ceramics and ultrasonic transducer manufacturer, dedicated to ultrasonic technology and industrial applications.
