Study On The Microstructure Of The Processing Surface Of The Fe-based Amorphous Nanocrystalline Magnetic Core With Laser Cutting

Fe-based amorphous nanocrystalline alloys have excellent soft magnetic properties and corrosion resistance,and their core products are widely used in electronic and electric power and other industries.The existing cutting method of Fe-based amorphous nanocrystals is diamond grinding wheel cutting,which has low processing efficiency.Laser cutting technology with the characteristics of fast cutting speed and high quality has been widely used in cutting various types of crystalline metal materials,and there are few applications related to cutting production of non-crystalline alloys.The laser cutting research on Fe-based amorphous nanocrystallines has important practical significance for improving the production efficiency of amorphous nanocrystalline cores.Therefore,the laser cutting process experiment is carried out to study the influence of laser process parameters on the surface morphology and microstructure of the Fe-based amorphous nanocrystalline core cutting surface,and combine it with numerical simulation analysis.Test and analyze the cutting surface with X-ray diffractometer,scanning electron microscope and laser confocal microscopy.The main results achieved after analysis and summary are as follows:1)Based on the characteristics and cutting quality requirements of Fe-based amorphous nanocrystalline cores,this thesis takes roughness,slag length,surface morphology of the cutting surface and microstructure of the cutting surface as the criteria for cutting quality,and mainly studies the influence of peak power,cutting speed,pulse frequency,gas pressure,defocus amount and other process parameters on the cutting quality of the core:(1)The laser cutting processing surface shows the morphology of ablation,streaks,nodules and slag,etc.,laser cutting will not destroy the physical phase structure of Fe-based amorphous nanocrystals,and is still amorphous phase and ?-Fe crystal phase.(2)With the increase of laser peak power,the roughness of the cutting processing surface decreases,the length of the slag decreases with the peak power first increases,and the number of slag increases first and decreases;the average grain size of the core without laser cutting is 11.9nm,and the average grain size range is between 40 nm and 65 nm after laser cutting;the peak power increases,which is conducive to inhibiting the amorphous crystallization of the cutting process and the growth of grains,and when the peak power is100%,the average grain size is 40.9nm.(3)When the cutting speed is 8.3 and 10mm/s,the flatness of the cutting processing surface is better,and only a small number of small nodules and slag appear at the lower end of the cutting surface;the cutting speed is further improved,the nodule appears close to the upper end,and the amount of slag is increased;the grain size of the Fe-based amorphous nanocrystals is insensitive to the cutting rate,and the laser cutting speed is increased,and the average grain size has a decreasing trend.(4)The roughness of the core processing surface increases with the pulse frequency,first decreases and then increases;the overall length of the slag on the processing surface decreases with the increase of the pulse frequency;the pulse frequency f=4250Hz,and the roughness value is smaller Ra=18.38?m;with the decrease of frequency,the amount of slag is significantly reduced;the surface quality of the cutting processing surface under the parameters of f=4250Hz and f=4000Hz is better,the cutting surface flatness is good,and there is no ablation;the average grain size is smaller at f=4500Hz,about 52.9nm.(5)As the gas pressure increases,the roughness and the length of the slag are shown as the trend of first decreasing and then increasing.When the air pressure is 1.2MPa,the roughness value is 16.17?m,the slag length is 0.4398 mm,the processing surface is flat,but there are more nodules and slags at the lower end of the processing surface;when the gas pressure is 1.6MPa,the roughness is 19.17?m,and the processing surface nodules and slag are significantly reduced,and better processing surface quality can be obtained;with the increase of gas pressure,the average grain size of the cutting surface shows a growing trend.(6)Compared with positive defocus,when using negative defocus to cut the core,the roughness and the length of the slag are smaller,the surface is relatively flat,and the overall surface quality of the cutting surface is better;the amount of defocus is negative,as the focus position is close to the lower surface of the core,the length of the slag gradually increases,the roughness decreases first and then increases,and the average grain size of the cutting surface shows an increasing trend;the roughness is smaller when the defocusing amount is2.75 mm,and the roughness is 12.64?m.2)In order to understand the temperature field distribution of the amorphous core laser cutting process,the melt solidification model and the multiphase flow model are used to simulate the three-dimensional temperature field of laser cutting in Fluent software by loading the rotating body heat source with a radius attenuated along the depth,and the morphology of the melting cut joint is obtained through the life and death unit method,and the influence of the cutting speed on the width of the cut joint and the thickness of the thermal affected zone is simulated.The simulation results show that:(1)Laser cutting Fe-based amorphous nanocrystalline materials are locally heated,and with the increase of laser power,the thickness of the heat affected zone increases as a whole,the heat affected zone shows a certain arc,and the thickness of the heat affected zone in the middle of the incision seam is the largest.(2)The power is certain,the cutting speed is increased within a certain range,the thickness of the heat affected zone is reduced as a whole,and the upper end surface is affected by the cutting speed less than the lower end face;under the condition of power2000 W,the laser cutting of amorphous nanocrystalline cores can obtain a cut width with good parallelism and a width close to the diameter of the spot when the cutting speed is20mm/s ? 25mm/s;the cutting speed is too small,which will lead to a larger cut width and uneven cut seam;the thickness of the heat affected zone at a cutting speed of 25mm/s is about 0.6mm.(3)The 1420K?1820K area is the material to remove the transition layer,and the actual cutting surface morphology,nodules,slag,etc.are formed in the transition layer under the action of laser and high-pressure auxiliary gas,and the thickness of the transition layer is about 0.3mm.