The cutter head of the synthetic diamond saw blade is made by powder metallurgy process, and the quality performance of the cutter head depends not only on the selection and ratio of raw materials, but also on the hot-pressing sintering process and the performance of the graphite mold. In this paper, the influence of the bulk density, impurity content, porosity, resistivity and other properties of mold graphite on the sintering quality of diamond bits during high temperature hot pressing sintering was analyzed. A new type of mold graphite processed by a special process is recommended. The hardness, bulk density and compressive strength of the surface layer of the mold made of graphite are higher than those of the middle part, which is beneficial to improve the smoothness and service life of the graphite mold, and thus is beneficial to improve the sintering quality of the diamond saw blade.
1. Hot pressing sintering
The cutter head for making synthetic diamond saw blades is to mix diamond single crystal and metal powder and other matrix materials uniformly in a certain proportion, and then cold-press to form, or directly put it into a graphite mold fixed by a frame, and then put it into a sintered mold. The purpose of hot pressing sintering is to make the matrix material diffuse and combine with metal particles at a certain temperature and pressure to improve its hardness and flexural strength. And enhance the ability of the matrix to be inlaid with diamond. During the hot-pressing sintering process, the temperature, pressure, temperature holding time, and whether the matrix material is lost are the four key factors that affect the quality of the cutter head.
2. Graphite mold
Because graphite products have a high melting point, their mechanical strength will not decrease but will increase at high temperature, strong chemical stability, good electrical and thermal conductivity and a series of excellent characteristics, therefore, in synthetic diamond tools and products. The hot-pressing sintering of drill bits and saw blades is made of graphite.
3. The influence of graphite on the quality of the cutter head
1. The influence of graphite bulk density, Shore hardness, flexural and compressive strength.
2. The influence of graphite open porosity.
3. The influence of impurity content in graphite.
4. The influence of graphite resistivity.
Fourth, the new mold graphite
According to the working conditions of the synthetic diamond cutter head in the hot-pressing sintering process, a special mold graphite was developed. This mold graphite can be greatly improved in performance indicators and uniformity after special processing. For example, high-quality raw materials are selected. It adopts fine grain or ultra-fine structure, and adopts ultra-thin single-piece molding process to increase the coke separation rate of the binder in the mold graphite and other special processes.
After the special process of graphite static processing of this special mold, the bulk density and resistivity of the single block are greatly improved, which is beneficial to improve the uniformity and stability of the quality of the cutter head, especially the binder of small pieces softens during roasting When decomposing, polymerizing and coking, the coke rate increases due to the oxidation of the binder, resulting in the formation of a coke layer on the surface of the graphite with a higher bulk density and strength than the interior, which is processed into a finished graphite mold after a small amount of grinding. After that, the hardness, bulk density and compressive and flexural strength of its surface part are higher than those of the middle part of the module.
