FEM Of Crack Defects In 3Cr2MnNiMo Steel Forging Process By Pan Huan

With the development of automobile,electronics and home appliance industries,the requirements for molds are gradually increasing.Therefore,the requirements for mold steel products are gradually increasing.However,the cracks in the die steel forging process and the void defects left in the metallurgical process have seriously affected the serviceability and service life of the product.Simulating the forging process of die steel with FEM technology,we can understand the generation and evolution of cracks and void defects,which is of great significance to actual production.The thesis was based on the "13th Five-Year" national key research and development programs "research and application of high performance tool steel",Taking 3Cr2MnNiMo die steel as the research object,the finite element simulation of surface cracks and void defects was carried out with ABAQUS finite element simulation software.The main work of this thesis is presented as follows:(1)By analyzing the distribution of stress and strain of forging during forging process,combined with the void growth ratio theory,it is found:in the forging process,the side surface of the forgings is subjected to tensile stress of the internal metal,and there is a possibility of producing cracks.The possibility of cracking in the axial center of the side surface of the forgings is most likely.The possibility of cracking can be reduced by reducing the friction between the forgings and the working anvil and increasing the height diameter ratio of the forgings;During the drawing process,the cracks possibly produced on the side surface of the forgings and the surface of forged parts which are not contacted with working anvil.(2)The upsetting process of the forging model with spherical void was simulated,it was found that the evolution process of the void located at the center of the forging was spherical?ellipsoidal?the both ends of the long axis were close to each other?the void was closed.The variation of stress and strain coincides with the evolution process of the void.(3)The affecting factors of the closure process of void included the shape of the void,the location of the void and the height-diameter ratio of the forgings;The larger the height-diameter ratio of the voids in the press direction was,the greater the critical relative reduction required when the voids were closed;The greater the equivalent strain of the void position was,the more conducive to the closure of voids;The smaller the height-diameter ratio forging was,the easier for the void in the same position for forging to close;The size of the voids and the starting forging temperature of upsetting process had little effect on the evolution of the voids;(4)Through the simulation of single press for cylindrical forgings with void defects with a wide anvil,it is found that the voids on center of the forging axis is most easily closed.The more critical relative reduction was needed when the void was closing to the end of the forging.It is more difficult for the void closed when the void was closing to the working anvil in the direction of the diameter of the forgings.With the upsetting and the wide anvil radial pressure combined,it had good effect for void closure.