Experimental And Numerical Simulation Research Of Temperature Field And Stress Field In 316L Stainless Steel By Laser Addictive Remanufacturing

Laser metal deposition has the advantages of high energy density,controllable heat input and high surface quality,compared with traditional processing technology.Therefore,the application of laser metal deposition in remanufacturing field has a promising application prospects.However,due to many factors effecting the processing of laser metal deposition,it takes a long time and costs a lot to acquire the excellent cladding depending on experiment exploration.Therefore,it is very important to study the numerical simulation technology about laser metal deposition in repairing 316 L stainless steel.The main research work is listed as follows:Laser metal deposition technology was used to repair trapezoidal grooves on 316 L stainless steel plates with a size of 50 mm×18 mm×10mm.An experimental study of the following two schemes was carried out.Scheme 1: The influence of laser power and scanning speed on temperature field and stress field in laser metal deposition process under the same energy density change.Scheme 2: Variation in microstructure and hardness of the first track in the first layer after the cladding process of the second track in the first layer and the first track in the second layer.The experimental results of the temperature distribution,stress distribution,microstructure change and hardness distribution under the above two schemes are achieved,and provide experimental verification of temperature field and stress field for numerical simulation.A finite element model of the temperature field of the trapezoidal groove repaired by laser metal deposition was established.The boundary conditions of the model were set reasonably.By comparing the numerical simulation results with the experimental results,it can be seen that the size and temperature field of the molten pool obtained by the numerical simulation are similar to the experimental results.The effect of laser power and scanning speed on the size of molten pool during laser metal deposition process under the same energy density was studied.And the size of molten pool in adjacent tracks under the same parameters was also studied.Based on the temperature field during laser metal deposition repair process,the finite element model of stress field is established by using thermal-structural coupling method.The effect of laser power and scanning speed on stress field during laser metal deposition process under the same energy density was studied.The simulation results are verified by comparing and analyzing the simulation results with the experimental results to ensure the accuracy of the model.The stress evolution and distribution of residual stress of repaired specimens using laser metal deposition under different technological conditions were analyzed.Using numerical simulation to predict the deformation of the 316 L stainless steel plate with trapezoidal groove repaired by laser metal deposition.The preheat treatment for the substrate before the experiment has been simulated,which can effectively reduce the deformation of the repaired specimens after laser metal deposition.Moreover,the simulation results indicate that the higher the preheating temperature is,the smaller the deformation of the repaired specimens will be.The accuracy of prediction of numerical simulation is verified by comparison with the results of experiments.The finite element model established in this dissertation can accurately and effectively simulate the temperature field and stress field under different process conditions,which provides a reference value for laser metal deposition processing.The model can effectively predict the effect of preheat treatment on the deformation of repaired specimens,which has guiding significance to explore the pretreatment process of deformation control of laser metal deposition.