Study On Forming And Simulation Of Hot Press / Hot Deformed Nd-Fe-B Permanent Magnetic Rings

Hot-pressed/hot-deformed Nd-Fe-B permanent magnet rings are widely used in the fields of permanent magnet motors,vehicular audio system and automobile sensor.However,the current simulation research on the forming process of hot-pressed/hot-deformed Nd-Fe-B permanent magnetic ring is relatively less,affecting the production efficiency and application prospects of high-performance hot-pressed/hot-deformed Nd-Fe-B permanent magnetic rings.This paper uses DEFORM-3D software to realize the numerical simulation of the upsetting deformation process of the Nd-Fe-B magnet,and then analyzes the influence of common factors on the performance of the forming part in the upsetting deformation of the Nd-Fe-B magnet.At the same time,the influences of forming process parameters and die structure characteristics on the effective stress,effective strain and material flow rate of the hot deformation Nd-Fe-B magnetic ring are studied.Finally,based on the grain evolution simulation,the hot-deforming process of the Nd-Fe-B magnet is discussed.The change of the average grain size is analyzed.The relationship between the microscopic average grain size and the grain distribution of the Nd-Fe-B magnet and the macroscopic effective strain is investigated.The main conclusions are presented as follows:(1)With the increase of friction coefficient,deformation,and blank height-to-diameter ratio,the maximum effective strain of Nd-Fe-B magnet increases,and the maximum effective stress shows a trend of first increasing and then decreasing.When the friction coefficient is 0.25,the uniformity of the stress distribution during the forming process of magnet is relatively good,and increases with the increase of the amount of deformation.The deformation speed has a relatively small effect on the effective strain of the formed magnet part,and with the increase of the deformation speed,the overall stress amplitude of Nd-Fe-B magnet gradually increases,but the influence of different deformation speeds on the stress distribution of Nd-Fe-B magnet is relatively small.(2)The friction coefficient and deformation speed mainly affect the effective stress and flow velocity of the Nd-Fe-B magnetic ring,but have a little effect on the effective strain.The increase of the deformation speed increases the effective stress and material flow velocity of the magnetic ring.In terms of die structure,within a certain range,the strain distribution of the Nd-Fe-B magnetic ring is more uniform,and the average strain value is lower with the increase of the punch fillet.The deformation speed of the Nd-Fe-B material decreases and the effective stress increases with the increase of the punch fillet.In the case of no punch fillet,increasing the die fillet alone will reduce the uniformity of the structure and strain distribution of the Nd-Fe-B magnetic ring,and increase the range of the stress concentration area.The flow velocity of the material will also increase with the increase of the die fillet,and the maximum value appears at the die fillet.The die gap mainly affects the effective strain of the Nd-Fe-B magnetic ring,and shows a little effect on the stress and velocity fields.With the increase of the die gap,the effective strain of the magnetic rings decreases and the strain distribution becomes more uniform.The stress,strain and velocity fields of the Nd-Fe-B magnetic ring are influenced by the pressure control plate component.After adding the pressure control plate,the effective strain of the magnetic ring increases,while the effective stress and the material flow velocity decrease.(3)The degree of grain refinement is the main factor affecting the effective strain of Nd-Fe-B permanent magnets.The results of grain evolution simulation show that the greater the degree of grain refinement,the smaller the average grain size of the magnet,and the greater the effective strain of the corresponding Nd-Fe-B permanent magnet.When the average grain size is not much different(namely,the degree of grain refinement is equivalent),the more uniform the grain distribution,the smaller the effective strain of the Nd-Fe-B permanent magnet.