Research On Filling Mechanism And Microstructure Evolution Of Helical Gear During Hot Forming

The helical gear is characterized by smooth drive,good meshing and high load carrying capacity,widely used in the industry of ships,automobiles,aerospace.Traditional machining method of helical gear,low material utilization ratio,long production cycle,low production cycle,is hard to meet industrial needs.Using forged techniques to produce helical gears,can shorten the production cycle and improve the mechanical properties of gears.In spite of this,there are still some problems to be solved urgently in the helical gear forging technology,the most important problems are the difficulty filling tooth corner and the large forming load.The hot forging of helical gear is a complex plastic deformation process under the action of coupling factors.Therefore,it is necessary to analyze the flow deformation behavior and micro-structure evolution law of some metal of the tooth shape,find out the reasons of difficult filling corner and large forming load during the hot forming process of helical gear,guiding the development of hot forging forming technology of helical gear.At first,the finite element simulation software DEFORM-3D is used to simulate the traditional closed forging process of helical gears.A 3D finite element model coupled with deformation-heat-transfer and microstructure evolution was used to analyze the deformation of grids,stress states,strain types,at different positions of helical gears in different forming stages,through the Flow-net and point tracking function provided by DEFORM-3D.It is found that the grids in the tooth shape are deformed to a large extent.With the increasing stroke,the three-directional compressive stress area expands.The Lode parameter of the center and tooth socket is positive meaning compressive deformation,and that of tooth root and tooth shape is negative meaning elongation deformation.The finite element method was used to analyze and determine that the tooth shape end shearing was a suitable forming scheme,and the flow characteristics of the material were obtained by the coordinate grid method in combination with the experiment of lead sample,the reliability of the scheme was verified.The distribution of recrystallization volume percentage and average grain size at different positions of tooth profile in the process of end shearing hot forging of helical gears under different process conditions was obtainedby DEFORM-3D,and the influence of process parameters on microstructure was analyzed,providing guidance for the regulation and control of the microstructure of helical gear hot forming.