Xiao Bing of Nanjing University of Aeronautics and Astronautics used high-frequency induction brazing method to use Ag-Cu alloy and Cr powder as the intermediate layer material, induction brazing in air for 35 seconds, brazing temperature of 780 °C, and realized diamond and A strong bond between the steel substrates. Yao Zhengjun and others used the method of induction brazing in Ar gas protection furnace, using Ni-Cr alloy powder as brazing filler metal, vacuum induction brazing for 30 seconds, and brazing temperature of 1050 °C to achieve a firm connection between diamond and steel substrate. Scanning electron microscopy and X-ray energy spectrometer, combined with X-ray diffraction structure analysis, found that during the brazing process, the Cr element diamond interface forms a Cr-rich layer and reacts with the C element on the diamond surface to form Cr3C2 and Cr7C3, which is to realize the alloy layer and Diamond has a major factor in higher bond strength. Grinding experiments are carried out with large depth of cut, slow feed and heavy load. From the surface morphology after grinding, no diamond is peeled off, and diamond abrasives are normal wear, indicating that diamond has high holding strength, suitable for For efficient grinding.
Taiwan China Grinding Wheel Co., Ltd. (KNIK.Inc) has introduced a single-layer uniform diamond high-temperature brazing bead. Under the condition of not reducing its life, the diamond dosage is reduced by 50% and the cutting speed is increased by 2 times.
Based on the research at home and abroad, the author's research group used Ni82CrBSi alloy sheet solder, which was evenly arranged on the solder sheet and brazed in a low-vacuum hot-press sintering furnace. A preliminary study on the brazed diamond tool was carried out. And explore how to apply brazing technology to impregnation tools. Starting from optimizing the arrangement of diamond in the carcass, the static structural parameters such as diamond particle size and concentration, and the dynamic parameters such as the effective diamond number and diamond spacing, the orderly arrangement of the single layer diamond in the transverse plane is realized, and then the lamination method is adopted. Disposed in the longitudinal direction, the diamond in the working layer has the ability to work continuously. In order to test the carcass' ability to insert diamond into the diamond, a diamond-inlaid drill bit was made for 5 times, and the maximum average edge value was measured. Through the test of the height of the diamond single-layer tool diamond (45/50 mesh diamond), it is found that the maximum edge value can reach more than 70%. It can be seen that the brazing technology can make the bonding strength between diamond and carcass greatly. improve. The results of the reinforced concrete drilling simulation experiment on the diamond drill bit (φ63mm) show that the drill bit can continue to work when the drill bit wears nearly 2mm. Theoretically, two layers of diamond have participated in the work, which seems to indicate that it can be realized. Pregnancy, the specific application process is still under further study.
3. Problems in brazing technology in the application of diamond tools
There are many difficulties that need to be solved during diamond brazing: 1 requires the brazing material to have good wettability and bonding strength to the diamond and the carcass; 2 the brazing material and the brazing process are selected to ensure the stability of the diamond to reduce or avoid The erosion of the diamond by the solder; 3 due to the large difference in thermal expansion coefficient between the diamond and the metal matrix, the welding residual stress is also large, reducing the strength of the joint; 4 the melting point of the solder is higher than the working temperature of the diamond tool, so it should be sought A metal (alloy) material with a lower melting point and a coefficient of expansion close to the diamond is used as the brazing filler metal, and some active elements are added to improve the wettability and affinity of the diamond to achieve the bonding of the diamond and the mechanical properties of the carcass. the goal of. In addition, key technologies such as the realization of diamond surface metallization, the matching and selection of surface metals and brazing fillers, and the selection of fluxes and gaseous media require further maturation and optimization.
The efficiency and life of the diamond tool depends on the firmness of the diamond abrasive particles being embedded, and also on the wear resistance of the carcass. The strength of the carcass itself, the distribution of diamond in the carcass, the concentration of diamond, etc. all have an effect on the wear resistance of the carcass. Therefore, how to make the carcass reach the ideal state is also a problem worthy of attention in the future work.
4. Conclusion
The brazing technology can realize the chemical metallurgical combination of diamond, bonding agent (brazing alloy material) and metal matrix interface, and has high bonding strength. Due to the high bonding strength at the interface, only a very thin bond thickness is required to firmly hold the abrasive particles, and the exposed height can reach 70% to 80%, which makes the utilization of the abrasive more fully and greatly improves the life of the tool. And processing efficiency. Compared with the conventional technology, the maximum allowable edge value of the diamond tool can be increased by more than 50%. Under the condition that the power consumption of the tool is not increased or decreased, the diamond consumption of the workpiece material per unit volume is reduced by more than half. Compared with electroplating tools, it also shows unparalleled advantages. In short, brazing technology has a good development prospect in the diamond tool manufacturing process, and this technology should be industrialized as soon as possible.
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