Fundametal Research On High-frequency Induction Brazing Of Diamond Wheels

Diamond tools have been extensively utilized in grinding hard and brittle materials such as stone, tungsten carbide, glass and ceramics, because of the excellent performances of Diamond abrasive, including extremely high-hardness, high-thermal conductivity, high-wearing feature and so on. However, owing to the limited storage space for chips and poor bonding force between diamond grits and matrix, it is not cost-effective with traditional multiplayer sintered and monolayer electroplated Diamond tools. Due to the chemical metallurgical reaction between grains and matrix, brazing diamond tools have sufficient storage space for chips and high bonding strength between diamonds and brazing filler. The monolayer diamond grinding wheels with rhythmed grain distribution are developed with induction brazing.The main contents in this paper are as follows:1. Experiment platform for high-frequency induction brazing diamond has been established, including inductor suitable to induction heating power, inertia gas protecting device. Based on the analysis of signal characteristics of thermocouple under strong electromagnetic disturbance, a real thermal potential representing the brazing temperature was obtained through the processing of signal conditioning circuit designed to regulate the measured signal, a temperature control system based fuzzy-control and virtual instrument was developed, the preparative work laid foundation of induction brazing process.2. The reaction products and the interfacial microstructure under the different conditions have been detected by scanning electron microscope (SEM), energy dispersion spectrometer (EDS), and X-ray diffraction (XRD), which combining with the tests of grinding granite and the compressive strength of the grain, processing parameters are recommended for brazing diamond with Ni-Cr filler alloy under high frequency induction heating. Performance of an induction brazed diamond wheel is remarkable than furnace brazed diamond tool while machining granite.3. Experiment devices have been designed and illustrated for induction brazing of diamond wheels, the method of local heating combine with continual revolving of the workpiece was adopted to fabricate the grinding wheel by plane inductor fixed with magnetic flux concentrator. During the process of induction brazing, small melting area of brazing filler alloy on the grinding wheel was achieved, the diamond grains could hardly be removed from their original position, which was key to acquire the monolayer diamond grinding wheels with rhythmed grain distribution.4. Experiments of grinding tungsten carbide were conducted to measure the grinding forces under different grinding parameters, and compared with the electroplated Diamond wheel. The experiment results illustrated the lower grinding force, and longer life could be reached with induction brazing diamond wheel than electroplated grinding wheel. Worn behaviour of the brazing diamond grits are traced in the whole grinding process, the fallout of Diamond grits was not found and the abrasion wear was the leading worn patterns of diamond grits, which indicates that the strong joining to the grains has been realized in the induction brazing, it will benefit to utilize the outstanding machining ability of Diamond superabrasive grains.