Numerical Simulation Of Electromagnetic Force In Laser Melting Deposition Enhanced By Electromagnetic Impact

Laser melting deposition(LMD)has broad application prospects in aerospace,medical equipment and other fields.However,due to its inherent characteristic---"transient melting process",microdefects such as residual stress and pores can be found in deposition layers,which restrict the promotion and application of parts.Therefore,magnetic field is introduced in laser melting deposition in order to reduce the pores or residual stress in workpieces.To study the method of laser melting deposition by electromagnetic impact,iron-based powder and 316 L stainless steel substrate were used.The concrete works completed in this paper are illustrated as follows:(1)The electromagnetic force of the deposition layer is derived theoretically.The mechanism of the method for reducing residual stress in deposition layer is analyzed based on the previous study on the formation and control of the residual stress in laser melting deposition.(2)Using finite element technology to analysis the time and space distribution characteristics of electromagnetic force in the deposition layer under the action of planar spiral coil.Carry out the research of the influence of electrical parameters and geometric parameters of the coil on the electromagnetic force.The application area of electromagnetic force is determined through the theory analysis,proposed the field shaper and optimization design of it was made.The simulation results indicated that a proper field shaper should equip with these characteristics: The upper surface radius is the same as the excitation coil radius;smaller lower surface radius and smaller inner hole radius.In addition,the electromagnetic force would be greater when the alternating current increased,which would be conducive to the impact of the effect.(3)Building the experiment devices according to the simulation results.The forming parts of single pass and multi-pass assisted by electromagnetic field under different excitation current were made and then made contrast to the conventional forming parts.(4)Analyzed the test results.Test results showed that: Magnetic field is beneficial for grain refinement,microhardness increasement,decline of quantities and average sizes of pores.The primary dendrite arm spacing(PDAS)decreased from approximately 5 to 3.2?m with electromagnetic field The residual stress is reduced by 49% compared to the conventional parts.