Design And Experimental Study Of The Device For Controlling The Porosity Of Laser Melting Based On The Aid Of Alternating Magnetic Field

With the rapid development of global equipment manufacturing industry,the working environment of important mechanical parts is becoming more and more complex.A large number of mechanical equipment are operating in high temperature,high speed,heavy load and corrosion environment.In this extreme condition,the surface of parts will inevitably appear wear,corrosion,fatigue and other failure behaviors.In order to improve the surface performance of parts and prolong the service life of mechanical equipment,surface strengthening technology came into being.Among them,laser surface strengthening technology has been widely used in the surface strengthening of turbine blades,aeroengine blades,gear surfaces,large rotor shaft diameter sleeves and other parts because of its advantages of high energy density,low energy consumption,no pollution,small thermal deformation of the matrix and high degree of automation.Laser remelting is an important branch of laser surface strengthening technology.It can effectively improve the comprehensive mechanical properties of metal materials by rapidly heating and cooling the surface of materials to obtain special microstructure surface coating.However,in the process of laser melting,due to the influence of air atmosphere and the great difference of material physical properties with temperature,defects such as pores and cracks are easy to appear in the melting layer.This will not only reduce the performance of the coating,but also shorten the service time of the coating,which seriously hinders the further development of laser melting technology.In order to solve the above problems,this paper designs a device to produce the intermediate frequency alternating magnetic field,which acts on the laser melting process of aluminum alloy,and studies the effect of the intermediate frequency alternating magnetic field on the porosity of the melting layer.(1)This paper discusses the causes of porosity defects during laser melting.The forms of electromagnetic force acting on conductive melt by different magnetic fieldsare put forward.The mechanism of alternating magnetic field accelerating bubble escape from molten pool is briefly analyzed.(2)According to the existing induction heating power supply in the laboratory,the structure and core material of the alternating magnetic field device are selected.The main parameters of the alternating magnetic field device are designed.(3)The COMSOL finite element model of alternating magnetic field device is established,and then the influence rule of coil turns,air gap length and pole shape on the alternating magnetic field is analyzed by COMSOL finite element software,and then the structure parameters of the device are optimized and adjusted.At the same time,the performance of the optimized alternating magnetic field generator is simulated and analyzed.The magnetic induction intensity distribution,temperature field distribution and Lorentz force distribution in the sample are obtained.(4)In the end,according to the optimized scheme,the intermediate frequency alternating magnetic field generator is manufactured,and the magnetic field strength and heat generation are tested.The error between the measured results and the simulation results is about 8%.The experimental results show that the porosity in the melted layer of aluminum alloy decreases about 80% under the action of 13 kHz and132 mT alternating magnetic field.