Research On Hot Precision Forging Process And Optimization Of Nickel Brass Gear Rings

The ring gear plays an important role in mechanical transmission structure.The precision forging forming technology has been widely adopted to fabricate these parts because of their complex working environment,various shapes and specifications,large batch,and strict quality requirements.However,some defects often occurred,such as under-filling and folding in the actual production process.In this paper,a typical ring gear part was selected,and the forming process of the gear ring part was analyzed by means of thermo-physical simulation experiment,finite element analysis and grey relational analysis.A multi-objective response surface optimization method for the ring gear part was proposed.The main work of this paper is listed as follow:（1）Study on the hot deformation behavior of the nickel brass material and the establishment of the processing map.The isothermal compression tests of the nickel brass alloy were carried out on a Gleeble-3500 isothermal simulation test machine at the deformation temperature of 873K～1073K and the strain rate of 0.01s^-1～10s^-1.The real stress and strain data were obtained automatically.Then the constitutive model and processing map were constructed using obtained flow stress data.The modified Arrhenius constitutive model considering the strain of compensation can describe the flow stress behavior of nickel brass alloy,effectively.Based on the observation of metallographic pictures and the theory of dynamic material model,the processing map was established under experimental conditions.The processing map provides the basis and reference for the selection of process parameters during hot precision deformation of synchronizer gear rings and to obtain good microstructure after deformation.（2）Analysis and research on forming technology of synchronizer gear ring forging process.This paper analyzed the cause of defects on a typical automobile synchronizer gear ring,DEFORM-3D software was employed to conduct numerical simulation analysis.As a result,the defects occurred in actual production such as under-filling and folding were reappeared through simulation,which explains the reason for the cause of defects,simultaneously.Therefore,position changing of billets has been put forward to avoid these defects,which can effectively improve the flow behavior of brass alloy from simulation results and lay the foundation for the subsequent optimization and improvement for final forgings.（3）Optimization of technical parameters during hot precision forging of synchronizer gear ring.The central composite experiment design method was conducted to design the experiment with the inner diameter of the billet,the height of the billet,the forming temperature and the pressing speed as the design variables,and the simulation experiment was carried out on DEFORM-3D software.Taking forging defects and filling condition,inner flash volume,outer flash diameter and maximum forming load as the optimization objectives,the grey relational analysis and entropy method were employed to transform the multi-objective problem into a single-objective optimization problem through the grey relational coefficient,and the model between the four variables and grey relational coefficient was established based on the response surface model.The influence of each process parameter on the objectives and grey relational coefficient was analyzed and the optimal process parameter combination for hot precision forging of nickel brass synchronizer ring was obtained.（4）Production verification of the synchronizer gear ring optimization scheme.The optimized process parameter combination calculated by response surface model was used for simulation.The simulation results showed that the synchronizer ring gear forgings were well deformed.In the actual production,the optimized process parameter combination and positioning were adopted.The forgings without any defects were obtained,reached the standard,and the rate of material utilization was increased by6.79%.The above content provides a material model for the simulation during hot precision forging process of nickel brass parts.The constructed processing map provides a certain basis for the selection of process parameters.And the optimization design scheme can also provide a certain reference for the process design optimization for similar synchronizer ring gear parts.