Analysis Of Folding Defects Of Track Link Forgings And Research On Restraint Measures

Track link products are widely used in excavators and other crawler transmission construction machinery,as well as in military equipment such as tanks and armored vehicles.It is one of the important components of the chassis part of the above type of mechanical equipment.The working environment of the track link is very poor and changes frequently,and it bears greater alternating stress and impact stress during use,so the track link needs better strength and wear resistance,and requires high quality of product processing and manufacturing.Defects such as cracks in track link products will reduce the strength and performance of the parts,and such crack defects will rapidly expand under the influence of alternating loads and make it scrapped during operation and affect the normal use of construction machinery.A certain type of track link produced by a company has a high proportion of forging and folding defects during the forging process,which greatly reduces production efficiency and increases material waste.This article analyzes and studies the forging process and die structure of the track link with the highest defect rate in actual production.In this article,first of all,the forging process of this type of track link is simulated and analyzed.The three-dimensional software was used for modeling and the same production process parameters and equipment parameters were used to establish the finite element analysis model of the track link forming process.The velocity field,stress-strain field and material distribution of each step of this type of track link are obtained by simulation.The forming result of the forging is consistent with the actual shape of the forging,which verifies the reliability of the model establishment and the credibility of the simulation analysis results.After that,the distribution of folding defects in the production of the track link was statistically analyzed in different region,and the cutting and erosion experiments were carried out on the folding defects at the sleeve holes where the defects mainly occurred.Through the point trace analysis of metal streamline distribution and corresponding numerical simulation,it is clarified that the material source and defect generation of the defect part are due to the quality defects of the end face of the shearing blanking staying in the forging die cavity and the material inside the cavity of the sleeve hole is laterally extruded to form a flow velocity intersection.Then,the blanks of different sizes and different states of end face are designed,and the end face lead angle experiment of the blanks designed for the analysis of the material flow at the end edges is carried out,so that the conclusions obtained by the above-mentioned defect analysis can be tested by actual production tests.According to the cause of the folding defects obtained in the previous analysis,the process parameters and die structure of the track link forging were optimized and designed.Firstly,the effect of friction and lubrication conditions on the forming size of the blank in the pre-form was explored.The variation law of the width and length of the pre-form step under different friction conditions is obtained.Proposed useful measures to increase the length of preformed preforms by improve lubricating conditions during the preform step.At the same time,an adjustment scheme for reducing the diameter of the original blank to increase the length is proposed,and the adverse effect of reducing the diameter of the blank on the filling effect of the track link during final-forging and the effect of suppressing the end surface defect when the billet is lengthened is analyzed and obtained and the data on the stretch of the blank in different sizes are also obtained.In order to further improve the rationality and effect of the pre-form process on the blank volume distribution,based on the requirements of the material volume of each part of the length of the track link forging,a pre-form process with unequal thickness flattening and limited widening at both ends of the forging is proposed.At the same time,the finite element simulation analysis of the key parameters and the combination of the shape of the pre-froming die constrained at both ends was carried out.By increasing the length of the blank,the influence of the defects on the end face of the blank on the folding defects in the forging process during shearing is eliminated,and the filling effect of the forging is improved and comparative analysis and obtained the best size parameter combination of preform die structure design.Secondly,the structure of the die at the sleeve end of the pre-forging step was adjusted,and it was proposed to shrink the size of the outer die cavity of the sleeve hole inward to improve the elimination of the defects of the blank end face during the pre-forging process.At the same time,the flat bottom punch skin of the current sleeve pre-forging die is designed as a inclined bottom punch skin.On the one hand,in order to store more materials in order to compensate for the problem of insufficient material outside the sleeve hole during final-forging step caused by the shrinking pre-forging die bore,On the other hand,it also improves the tendency of the confluence and folding of the exit area of the punch skin caused by the violent outflow of material during the pre-forging punching of the flat bottom punch skin structure.The adjustment of the structure of the pre-forging die,on the premise of ensuring the forming and filling of the final forging,not only reduces the stopping of the original defects on the end face of the blank in the die forging cavity,improves the suppression effect of folding defects,but also improves the rationality of the sleeve end’s flow of materials near flat bottom punch skin in die forging process.In this paper,the actual production is combined with finite element simulation technology and production test verification,and the defects of the cut forging are analyzed and fed back to the numerical simulation analysis to determine the cause of the defect.Then the process conditions and die structure improvement schemes are proposed through numerical simulation to guide the actual production,the above works improves the forming quality of the track link forgings,improves the production efficiency and reduces the production cost,and the thesis research has important application value.