Research On The Polishing Law Of 45 Steel Scanning Electron Beam Bevel

45 steel has special plasticity and toughness,high strength and good cutting performance.It is commonly used in shafts,bolts,couplings,medium precision plastic mold steel and other parts.In practical application,it is often affected by the shape of the material surface and the working environment,which aggravates the surface wear and corrosion of the material.Scanning electron beam bevel polishing can effectively reduce the surface failure.According to the distribution characteristics of the heat flux of the oblique polishing of the scanning electron beam,based on the heat conduction differential equation and the elliptical Gauss heat source model.The physical and mathematical model of the temperature field of scanning electron beam bevel polishing is established to simulate the thermal action process of scanning electron beam on different angles of bevel.The distribution characteristics of the temperature field of different angles of bevel are obt ained and the distribution law of the temperature field is explored.The reasonable parameters were determined to study the different bevel of 45 steel by scanning electron beam polishing.The surface roughness,wear resistance and microhardness of the mod ified layer were tested,The microstructure of the modified layer was analyzed and studied before and after polishing with different angles by scanning electron beam,and the influence of process parameters such as beam flow and scanning speed of electron beam on the surface roughness,the modified layer,the hardened layer microstructure and wear resistance of 45 steel with different angles were discussed.The research results show that: the thermal action process of electron beam polishing is rapid heating and rapid cooling;in the thermal action area of electron beam polishing,the surface temperature field is in dynamic equilibrium,and the temperature gradient of the thermal action area is relatively large,its value can reach 820 K / mm.When the electron beam current is less than 8m A,corresponding to the inclined surface with different inclination angles ranging from 0° to 15°,as the electron beam current increases,the surface roughness gradually decreases.When the sample is flat and the beam curre nt is8 m A,change the surface roughness after the reduction is 51.4% lower than the original surface roughness.When the sample is inclined at an angle of 15° and the beam current is8 m A,the surface roughness is 70.1% lower than that without electron bea m modification;the microstructure of the modified layer is needle-shaped martensite and Structure of lath martensite mixed phase;when the sample is flat,the maximum hardness value is 846.7Hv is about 2.73 times that of the matrix,when the sample is inc lined at an angle of 15°,the maximum hardness value is 747.6Hv,which is about the matrix 2.4 times the scanning speed;when the scanning speed is 2.5mm / s,with the increase of the inclination angle of the inclined plane,the surface roughness of the modified material will increase and slower than the original surface roughness;when the scanning speed is 3mm / s ～ 3.5 mm / s,with the increase of the scanning speed and the inclination angle,the surface of the treated sample material is rougher than the original surface;the modified structure is transformed from the mixed phase of coarse needle martensite and lath martensite into Mixed phase of hidden needle-shaped martensite and retained austenite;as the inclination angle c hanges in the range of 0° ～ 15°,the amount of wear gradually increases,and the amount of wear depends on the microstructure and microhardness of the modified layer.Scanning electron beam bevel polishing can reduce the surface roughness of the material for the bevel of 0° ～15°,and the wear resistance and micro hardness have also been significantly improved.Scanning electron beam polishes inclined planes with different angles.It can reduce the surface roughness of 45 steel,improve the surface hardness and wear resistance.This method provides a good theoretical basis for the development of a new bevel polishing and modification.