The Research Of Electric Upsetting Forming And Die Forging Process On Intake Valve Of 85Cr18Mo2V

The intake valve is used to exchange gas and seal the combustion chamber for diesel engine. The electric upsetting forming and die forging process of diesel engine intake valve is very complex.Many process parameters which may be effected and interacted with each other are involved in the process.In the course of electric upsetting,many defects of work piece can easily be appeared,such as coarse grain,over-heating and over-burnt,head fold,head skew,crack etc.These defects which caused by electric upsetting will serious affect the subsequent die forging and its usability.This paper mainly adopts a method that combines theoretical analysis,numerical simulation and experimental research,to study the forming process of intake valve of 85Cr18Mo2 V.A experimental study was carried on the workpiece which have head cracks with upsetting by the means of OM,SEM and EDS.The results show that the grain was coarse and unevenness in the end face of workpiece.And the boundary of grain appear the melting and over-burnt.The cracks were extended along the grain boundary form the surface to the interior with a irregular path.The intergranular corrosion of material was serious happened.These are due to the heating temperature which in the upsetting process is too high.A large number of inclusions which contain Ca and Al were existed on the grain boundary,and present a segregation phenomenon.On the basis of summarizing the previous test,performing numerical simulation to the electric upsetting process of intake valve by the Deform software of finite element simulation.By simulating the laws of equivalent strain and stress,metal flow in the process of upsetting under different upsetting speed and heating temperature,can acquire the optimized paremeters of upsetting which are the upsetting cylinder speed is 18mm/s,the anvil speed is 2mm/s,the initial distance a is 20 mm,the heating temperature is 1100℃.By the optimizing parameters can obtain a upsetting workpiece with good forming.Then simulating the influence of process parameters of die forging under different forging temperature and upper die speed.The result shows that the filling is best when the forging temperature is 1150℃,the upper die speed is 50mm/s,the temperature of anvil and mode is 350℃ and the friction coefficient is 0.2.Performing the electric upsetting and die forging to the bar of 85Cr18Mo2 V using the optimizing process parameters,can get a good forming valve.The size of valve conform to the requirement of drawing,and the surface without defects of cracks,folding,burnt etc.The internal organization of valve were even and without micro crack.The results are consistent with the simulation.The conclusion of this paper have a guiding signification to opitimize the process parameters and improve the manufacturing quality of intake valve.