| Because of its high strength and high wear resistance,cemented carbide is widely used in the production of tool materials.The traditional grinding process is easy to cause defects such as burns and cracks on the surface of the blade.The surface roughness of the processed blade is relatively high,which directly affects the performance of the tool.In addition,before the tool coating,it is necessary to improve the surface quality of the tool so that the coat ing and the tool substrate are tightly bonded and will not fall off.Therefore,the tool surface needs to be polished to obtain a surface with lower roughness and no obvious defects.In this paper,the magnetic field-assisted shear thickening polishing met hod is used to polish cemented carbide inserts.The main research contents are as follows:（1）The mechanism of the magnetic field-assisted shear thickening phenomenon was expounded,and corn starch/water was used as shear thickening medium,carbonyl iron powder was used as magnetic field-assisted particles,diamond particles were used as abrasives,potassium sorbate and polymer were prepared.Magnetic field assisted shear thickening polishing liquid with sodium acrylate as additive,and the rheological properties of the prepared polishing liquid were tested and analyzed.The experimental results show that under the excitation of a weak magnetic field,the polishing liquid exhibits a better shear thickening effect than that without a magnetic field.The viscosity of the polishing liquid increases with the increase of the magnetic field.Under the action of a strong magnetic field,the magnetic field effect will be suppressed.The increase of carbonyl iron powder mass fraction and diamond abrasive particle siz e will inhibit the thickening characteristics of polishing liquid.（2）Using the Gaussian multimodal function to fit the rheological characteristic curve of the magnetic field-assisted shear thickening fluid,and bringing the fitted function into Fluent to simulate the fluid flow of the polishing fluid,and analyze the blade surface during the polishing process of stress.The simulation results show that the dynamic pressure distribution on the workpiece surface is proportional to the polishing speed and inversely proportional to the magnetic induction intensity.An increase in the polishing groove speed and a decrease in the magnetic induction lead to an increase in shear stress.By comparing the product of shear stress and velocity with and without a magnetic field,it is proved that the magnetic field-assisted shear-thickening polishing has a higher material removal rate than the traditional shear-thickening polishing under the action of a weak magnetic field.（3）A magnetic field-assisted shear thickening polishing device was developed,and the effects of polishing process parameters such as workpiece placement,polishing speed,magnetic induction intensity and abrasive particle size on the blade surface quality and material removal rate were studied throu gh single-factor experiments.The experimental study shows that when the workpiece is placed vertically,the surface of the workpiece can obtain a lower and more evenly distributed surface roughness;the increase of polishing speed will lead to the decreas e of the surface roughness of the workpiece,and the material removal rate increases with the increase of shear stress.The increase of the magnetic induction intensity has little effect on the surface roughness,but it will reduce the material removal rat e;the smaller the abrasive particle size,the better the surface quality of the blade and the higher the material removal rate can be obtained.Through the orthogonal test analysis and the actual situation,the optimal polishing solution formula and proce ss parameters are obtained.After polishing the cemented carbide insert for 15min,the surface with Ra ABC of 15nm and Ra D of 32nm can be obtained,and the material removal rate can reach 12.6μm/h. |
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