Experimental Study On Cutting Performance Of Textured Tools Under Magnetic Cutting Fluid

During the cutting process,the plastic deformation of workpiece and the sharp friction between tool and chip will generate amount of cutting heat,which leads to rapid wear of tool,and causes "sticking knife" phenomenon by softening the material of workpiece,reduce the life of tool and the quality of workpiece.Therefore,improving the friction state between tool-chip and reducing the cutting heat have become an important part of cutting research.At present,cutting fluid is widely used to cool and lubricate cutting area in practical engineering.However,due to the high temperature and high pressure environment in the cutting area and the close contact between tool and chip in the internal friction area,at the same time,the low velocity and pressure of cutting fluid in the traditional cooling mode,it is difficult to enter the critical friction area between tool and chip,causes the use efficiency of cutting fluid very low,and the environmental pollution problem arises.In order to solve this problem,this paper combines laser micro-texture technology with magnetic cutting fluid cooling and lubrication technology,puts forward a new scheme of cutting tool texture and cooling and lubrication,carries out relevant simulation and Experimental Research on the basis of relevant theoretical basis.The main research work in the thesis is as follows.(1)Firstly,the basic theories of metal cutting is systematically introduced,including cutting deformation,cutting force and heat,tool wear,etc.The key area for the preparation of tool surface texture is pointed out,which lays foundation for the analysis of turning test.Secondly,by calculating the viscosity and heat transfer mechanism of nano-magnetic fluid with or without magnetic field,the gradient magnetic field environment is analyzed as an important condition to improve the cooling and lubrication performance of magnetic cutting fluid.In this paper,the high-speed steel cutting tool is magnetized in a uniform magnetic field and high gradient magnetic field is formed around and on its surface.Because of the tip effect of magnetic field,the high magnetic induction intensity corresponds to the critical friction zone of tool-chip.Under the magnetic attraction,the magnetic cutting fluid enters the critical friction zone of tool-chip,thus effectively improving the cooling and lubrication effect of the magnetic cutting fluid.(2)The magnitude of magnetic induction affects the attraction effect of magnetic field to nano-magnetic cutting fluid,so improving the intensity of magnetic induction field is an important basis for magnetic system design.The air gap of magnetic system is adjustable and easy to install on lathe.According to the principle of magnetic circuit design,the optimum structure of magnetic system is designed and determined by Maxwell finite simulation and measurement verification.The distribution of magnetic field around high speed steel tool and gradient magnetic field on the surface of tools with different textures are analyzed.It is found that the magnetic field around the tool placed in magnetic system can be divided into reversed magnetic zone and paramagnetic region the tool.and the tool rake face is in the paramagnetic region;the insertion of texture significantly improves the magnetic induction strength of tool surface,and further increases the magnetic field gradient.The texture enhancement effect of textured surface is more significant.(3)The high speed steel W6Mo5Cr4V2 was used as experimental material.In order to obtain ideal laser surface texture,the laser texture process test was carried out systematically.Microgroove texture and texture were fabricated by picosecond laser processing system and SPI fiber laser processing system respectively.The influence of pump current and scanning speed of picosecond laser on the width and depth of micro-groove morphology,and the influence of pulse width and power of SPI fiber laser on the diameter and height of textured morphology were investigated.Laser processing parameters matching texture morphology and size were obtained,and suitable laser processing parameters were selected to fabricate texture cutting tools.(4)Nano-magnetic cutting fluids were prepared and metal cutting experiments were carried out.The cutting performances of non-textured,micro-groove textured and textured wool cutting tools were compared under the conditions of non-magnetic environment general cutting fluids,non-magnetic environment magnetic cutting fluids and magnetic field environment magnetic cutting fluids.The cutting force,friction of rake face,tool-chip bonding,chip morphology and cutting temperature were analyzed.The experimental results show that: firstly,magnetic cutting fluid under magnetic field can be attracted by magnetic force,and enter into the critical friction area of tool-chip through the drainage of micro-groove texture or the adsorption of wool texture,improve the friction state between tool-chip and reduce the cutting temperature;secondly,The friction coefficient and cutting temperature of micro-groove texture cutting tool under magnetic cutting fluid in magnetic field environment are obviously lower than those under non-magnetic cutting fluid.The friction coefficient and cutting temperature of micro-groove texture cutting tool under magnetic cutting fluid in magnetic field environment are reduced by 23.4% and 17.4% respectively.Finally,the lubrication and cooling mechanism of textured cutting tools under magnetic cutting fluid is analyzed.