Studies On Energy Transfer And Accumulation Of Selective Laser Melting

Selective Laser Melting is one of the rapid prototyping technologies. It focuses on three-dimensional molding manufacture in the field of metal materials. In this process of machining, the moving centralized laser heat source and complex material thermal physical properties will result in uneven temperature field and cause process defect because of Excessive or insufficient energy input, so it is of great significance for mastering of the complex transfer form of temperature and selecting process parameters to study temperature field with the finite element method.Analyzed the operation condition of the selective laser melting process, found that complex material properties, load of mobile laser heat source, absorption and release of metal latent heat have an important impact on the energy transfer. In the case of considering the above factors, the simulation model of three-dimensional nonlinear transient temperature field of 316L stainless steel powder was established in this paper. Single scanning, multi-tracks scanning and multi-layer scanning are done using this model, then observe the surface morphology of sintered specimen of SLM to illustrate the correctness of the simulation. The main contents as follows:1. By the dynamic analysis of energy transfer in the process of selective laser melting, it is necessary to distinguish the material properties between powder and entity about 316L stainless steel. Achieve the assignment of material properties from the state of powder to the state of the entity using subroutines of ABAQUS, making the material thermal physical parameters can change along with the change of temperature and material status. And state variable is added in the subroutine, thermal conductivity between the material starting melt and complete melting can be carried out in accordance with the entities and powder the proportion of the assignment, so the simulate results can get the melting degree of the results of the edge.2. Single scan simulations are finished with the model. According to melt the edge width, laser power can be divided into three intervals:insufficient energy, moderate energy, high energy. And then, multi-tracks scanning is performed, the energy transfer and accumulation can be seen from the curve of temperature changes over time of multi-tracks scanning. The effects of overlap rate to energy accumulation are also analyzed.3. Realize the multi-layer scanning simulation combined the element birth and death technique, the mutual influence between layer and layer are analyzed; Compared with full powder model and the model of powder containing the entity, get conclusion that the entity in the powder bed have the effect of drainage.4. Manufacture the design specimen with Selective Laser melting equipment and observe the surface topography of the specimen, prove the validity of the simulation.