Graphite electrode material selection is based on a lot, but there are four main criteria:
1.Average particle diameter of materials
The average particle diameter of the material directly affects the state of the discharge of the material.
The average particle size of the material is smaller, the discharge of the material is more uniform, the discharge condition is more stable, the surface quality is better. For surface, high precision forging, die-casting molds, are usually recommended, the coarse grain materials, such as ISEM-3 etc.; for higher electron mold surface, precision requirements, recommend using average particle diameter in 4 m below the material, to ensure that by mold machining accuracy and surface finish. The average particle size of the material is smaller, the loss of the material is smaller, the greater the force between the ionic groups. For example: usually recommended in precision casting mold, forging mold, ISEM-7 has been sufficient to meet the requirements; but the customer for the accuracy is very high, to ensure that the smaller the material loss, so as to ensure mold precision and surface roughness. At the same time, the larger the particle, the faster the discharge rate, the smaller the loss of rough machining. The current intensity of the discharge process is different, which leads to the different energy of the discharge. But the surface finish of the discharge is also changing with the change of the particle.
2.Flexural strength of materials
The flexural strength of the material is the direct embodiment of the strength of the material, which shows the close degree of the internal structure of the material. The high strength of the material, the loss of its discharge performance is relatively good, for the high accuracy of the electrode, as far as possible to choose a better strength of the material. M1 can meet the requirements of general electronic connector mold, but some have special precision electronic connectors die, you can choose the same particle diameter, but slightly higher strength material M2 material.
3.Shore hardness of materials
Graphite is generally considered to be a relatively soft material in the subconscious mind. But the actual test data and application shows that the hardness of graphite is higher than that of the metal material. In the special graphite industry, the general hardness test standard is the shore hardness measurement method, the test principle and the metal test principle is different. Due to the layered structure of graphite, it has excellent cutting performance in the cutting process, the cutting force is only about 1/3 of the copper material, and the surface is easy to be processed after machining. However, due to its high hardness, cutting, the loss of the tool will be slightly larger than the cutting metal. At the same time, the hardness of the material in the discharge loss control is relatively good. In our EDM material system, for the application of more of the same size have two materials are available, a kind of hardness is slightly higher, a hardness is slightly lower, to meet the needs of a variety of different requirements of customers. . Mainly taking into account the various types of customers for discharge And the direction of mechanical processing.
4.Intrinsic resistivity of materials
According to the characteristics of the material for the statistics, if the average particle size of the same, the resistivity of the discharge rate will be smaller than the resistivity of the slow. For the same average particle size of the material, the resistivity of small materials, its strength and hardness will be slightly lower than the resistivity of the material. That is, the rate of discharge, the loss will be different. Therefore, it is very important to choose the material according to the practical application.
Because of the particularity of the powder metallurgy, the parameters of each batch material have a certain range of fluctuation. But the same grade of graphite materials, the discharge effect is very close, due to various parameters caused by the difference in the effect of the application is very small.
The choice of electrode material is directly related to the effect of discharge, to a large extent, the selection of materials is appropriate, determine the discharge speed, machining accuracy and surface roughness of the final.
These four kinds of data represent the main discharge performance of the material, and directly determine the performance of the material.