Investgation On Temperature And Stree Field Of Selective Laser Melting Of H13 Steel

The process of Selective Laser Melting?SLM?is relatively simple and it has a good development prospect for it's used to a wide range of metal materials.This method can shorten the production cycle and make the near full-density of parts.The formed parts can be directly put into use without any post-processing or simple post-processing.Compared with the traditional manufacturing process,the performance of parts manufactured by this technology can be better in all aspects.In this paper,a lot of H13 steel samples were prepared by SLM and the microstructure and properties of the samples were observed and analyzed.Then the finite element software ABAQUS was used to analyze the temperature field,pool topography and stress field,which is hardly observed during processing.The results show that the sample with the maximum density of 97.47%was obtained by experimental.It was found that the density increased with the increase of laser power at the beginning and then decreased slightly,the density decreased with the increase of scanning speed.The sample showed defects such as spheroidization,unmelted and unfused.The main microstructures were martensite and a range of several micrometers to several tens of micrometers strips-shape and cells-shape substructures existed inside the crystal grains of sample.In terms of the temperature field of numerical simulation,the main thermo-physical parameter affecting the highest temperature(T_max)is specific heat capacity,while thermal conductivity affects the cooling rate.In terms of the stress field,the main mechanical performance parameter affecting stress field is thermal expansion coefficient.The smaller the solid volume under the powder bed,the worse the heat dissipation effect,but it can reduces the stress during processing.During cooling,the isotherm of the powder-solid boundary and the nearby area appears"concave".The T_max and the size of molten pool increase with increasing laser power and decrease with increasing scanning speed.The heat accumulation of the multi-pass scan will gradually increase the T_max of each pass.Based on the calculation results of temperature field,the sequential coupling coupling method is used to calculate the stress.It is found that the stress distribution is anisotropic and mainly along the direction of laser movement.The residual stress increases with the increase of laser power and decreases with the increase of scanning speed.It is found that the simulation results are in good agreement with the experimental results.The simulation results can roughly reflect the trend of residual stress with process parameters and have a certain reference value.