The Numerical Simulation Of Hot Forging And Technique Optimization For Car Crankshaft

As one of the core components of the automotive engine,it corporate with connecting rod to change the gas pressure acting on the piston into a rotating power in order to provide power for the car.It belongs to the typical complex difficult forgings in die forging production,where the high mechanical properties and surface quality are demanded.However,the complex layout of the die cavity will lead to the emerging of forging deflects such as folding and filling dissatisfaction.The hot forged crankshaft proposed in this paper is made of non-quenched and tempered steel TL1438.Billet of the crankshaft is drop into the forging process directly after intermediate induction heating without rolling forging blanks.Also,it can achieve good mechanical properties and microstructure crankshaft without the subsequent heat treatment after forging.However,the main issue in producting crankshafts with one-cavity forging dies is to ensure the quality of the forging and to extend the service life of the die.In this paper,finite element numerical simulation technology has been taken in order to analyze the hot forging process and to optimize the tool of crankshaft.The two hot forging processes of crankshaft were analyzed based on the finite element simulation technology.Firstly,the one-cavity forging dies of crankshaft were designed,the simulation results show that the forming load and tool wear depth were serious,however,it still can not full in the position of crankshaft balance block.Therefore,this paper optimize the die structure,adding dressing position in the die cavity neck in the pre-forging.The simulation results show that the balance block position of the crankshaft filling well,but the forming load and tool wear were still high.On the basis of the analysis,the primary press-speed of presses was selected and analyzed the main factors to impact the forming load and the tool wear depth.The design parameters of pre forging die for crankshaft were optimized by using response surface method.The Box-Behnken design method was used to design the experiment project,with the three factors: the dressing radius,the blank radius and the flash thickness,and the two responses were the pre forming load and tool wear depth in the forging.The numerical simulations were carried out and the sample set was eatablished.Response surface models were obtained by fitting and the thickness of the crankshaft flash was selected based on the optimization results.In addition,the study shows that the blank preheating temperature,tool preheating temperature and fraction coefficient have an effect on the crankshaft forging filling effect,forming load tool wear.Therefore,using Box-Behnken design method to design the experiment project in order to optimize the crankshaft process parameters,with the three factors: the blank preheating temperature,tool preheating temperature and fraction coefficient and the two responses: the maximum of forming load and tool wear depth in the forging.With the numerical simulations executed and the simple set estimated,response surface models were obtained by fitting.The optimal combines of factors were obtained when the response is minimized.The results showing that the forming load and tool wear depth of the die were significantly reduced,which provided a reference for the tool design and hot forging process of crankshaft.