The quality of the graphite mold and the shaking size of the graphite performance parameters directly affect the dimensional accuracy of the artificial diamond cutter head, the appearance shape, the content of binder in the cutter head, the hardness of the matrix data, the bending strength, the bezel setting ability of the diamond, and the cutting performance and service life of the cutter head.
1. The influence of graphite bulk density, shore hardness, flexural and compressive strength.
When graphite plays a role in mold support in the hot pressing sintering process, the higher the bulk density, shore hardness, flexural and compressive strength of graphite, the better, and the bulk density should be greater than 1.75g/cm3. As the indenter of the mold, the level of its bending strength is more important. If the bulk density of graphite is low, its hardness, flexural and compressive strength will be correspondingly lower, and it can be easily fractured or fractured in use.
2. The influence of graphite opening porosity.
In order to ensure the finish of the cutter head, in addition to the high surface finish of the graphite mold, the particle structure of graphite is also required to be fine, and the smaller the opening porosity, the better, which should generally be less than 13%. If the bulk density of the mold graphite is low and the porosity is too high, in the process of hot pressing and sintering, the graphite will absorb more metal bond in the cutter head and turn it into metal impregnation of graphite, so that the weight loss rate of the cutter head is added, thereby changing the ratio of metal bond and diamond in the cutter head, and reducing the manipulation ability of the binder to the diamond. Even the adhesion between the surface of the cutter head and the graphite mold occurs, reducing the finish of the surface of the cutter head.
3. The influence of impurity content in graphite.
Graphite, which is used as a hot-pressed sintering mold, requires its ash content to be as low as possible and the degree of graphitization to be as high as possible. If the impurity content in the graphite is too high and the ash content is too large, the excess impurities in the graphite mold will react with the metal binder in the cutter head during the hot pressing sintering process, and adhere to the appearance of the diamond bit, resulting in dark red traces, which will affect the appearance of the diamond bit.
4. The influence of graphite resistivity.
When the graphite mold is used as the electric heating element of the artificial diamond cutter head in the hot pressing and sintering process, the resistivity between the graphite blocks and between the various indenters is required to be common and the uniformity is high. If the resistivity of graphite blocks is not uniform, according to Joule's law, the heat generation between blocks and groups will be different, and the temperature will increase. In the hot-pressing sintering process of the diamond cutter head, the temperature will lead to the difference in the hardness and flexural strength of the matrix data, and will also lead to the difference in the strength of the bezel setting ability of the matrix to the diamond, which will affect the wear ratio and cutting ability of the cutter head.