Simulation Analysis Of Temperature Field And Stress Field Of 3D Printing Mold Parts Cracking

Metal 3D printing is an advanced manufacturing technology developed in recent years.In theory,it can print parts with any complex spatial structure.Existing mold manufacturers have applied metal 3D printing technology to the manufacture of complex mold parts.To solve some problems such as difficult processing,long processing cycle and high cost.However,in actual production,the thermal stress during the printing process will cause the parts to crack,which seriously affects the application of metal 3D printing technology.Therefore,this article focuses on the cracking problem of 3D printing 420 stainless steel mold parts.The main research contents are as follows:(1)First,by establishing a single-layer simulation model of the 420 stainless steel printing process,the molten pool shape,temperature field,and stress field under different laser power,scanning speed,and substrate preheating temperature were simulated and analyzed,and it was found that the molten pool increases with the increase of the laser power,and decreases with the increase of the scanning speed.The temperature and temperature gradient of the laser action area increase with the increase of laser power,and decrease with the increase of scanning speed.The stress when cooling to room temperature increases with the increase of laser power,and decreases with the increase of scanning speed.Increasing the substrate preheating temperature will extend the time for the printing layer to cool and shrink and produce stress,and the stress when cooling to room temperature is significantly reduced..(2)Then,based on the structural characteristics of the cracked mold parts,a simulation model of the cracked mold parts is established,and the temperature field and stress field of the mold part printing process are simulated,and the thermal cycle and stress cycle process at different positions of the part are analyzed with emphasis.The printing cracking process of mold parts is analyzed.It is found that the thermal cycling effect during the printing process causes the stress to periodically fluctuate.As the number of printing layers increases,the stress accumulation at the corners and corners caused by the cooling shrinkage.When the maximum stress exceeds the strength limit of the material,initial cracks appear in the parts,expand gradually under the action of stress.By reducing the laser power and substrate pre-heat treatment,the maximum stress and fluctuation range can be effectively reduced,and the adjusted process parameters are used to print out well-formed mold parts.(3)Finally,in view of the poor plasticity and toughness of printed 420 stainless steel,tempering heat treatment experiments were carried out,and the effects of different tempering temperatures and cooling methods on the microstructure and properties of 420 stainless steel were discussed.It is found that as the tempering temperature increases,the strength and hardness of the material first increase and then decrease.When the tempering temperature is above 550°C,the strength and hardness of the material decrease significantly,and the ductility is improved.When the tempering temperature is 350?,the impact toughness of the material is the best.Compared with air cooling with furnace cooling,the cooling rate is significantly reduced,which is conducive to the decomposition and dispersion of carbides in the structure,and improves the strength and hardness of the material.