| As a new type of surface treatment technology,laser cleaning has the advantages of green environmental protection and strong cleaning ability compared with traditional pickling and physical decontamination.Surface pollutants can be quickly removed after pulse laser irradiation,which is widely used in metal surface cleaning and pretreatment.In the production of polycrystalline silicon,a thin layer of pollution will be formed on the metal surface of the inner wall of the reduction furnace.If the metal surface is not cleaned in time,the metallic lustre of the inner wall will be reduced and the energy loss in the production process will be increased.Therefore,on the basis of not damaging the original performance of the substrate,it is of great significance to remove the metal surface pollutants and improve the surface gloss.The main research contents carried out in this article are as follows:In this paper,the 316L special steel for base material of polycrystalline silicon reduction furnace is used as the cleaning substrate,and experimental sample preparation is carried out by simulating the main environmental conditions in the reduction furnace.At the same time,the laser cleaning experiment platform is designed and built according to the existing basic research equipment.Through the adjustment and control of the experiment platform,the process parameters are effectively quantified to provide reliable support for subsequent experiments.Moreover,the simulation physical model is established through COMSOL finite element software.Meanwhile,the boundary conditions are set and the grid is divided.And then the temperature field during laser cleaning is simulated.After that,the temperature curve change trend is analyzed,and the simulation result is verified.The physical model of laser cleaning is simplified and analyzed for the transient thermal expansion mechanism and ablation mechanism in the microcosm.In addition,a four-factor and four-level orthogonal experiment is conducted by using the laser cleaning experiment platform,and the results of multiple orthogonal experiments are compared and analyzed to initially optimize the better process experimental parameters.In order to ensure the comprehensive experimental process and reliable result,forty cleaning process experiments are successively conducted on the preliminary optimized process parameters.As for the experimental results of different cleaning times,the gloss evaluation is made preferentially from the macro perspective,and the removal rules of surface pollutants of the experimental samples are observed.Then the surface morphology and element composition under the micro interface are analyzed by means of SEM,EDS,XRD and other detection methods,and the optimal surface and process experimental parameters are determined through the joint evaluation of macro and micro interface.Finally,in order to observe the effect of laser cleaning technology on the metal surface,the surface is tested for corrosion resistance and hardness.The results show that the temperature field can reflect the photothermal mechanism of the substrate surface irradiated by pulsed laser,and the accumulated temperature of the substrate does not damage the surface.In the microscopic mechanism simulation results,there is a large transient temperature gradient between the substrate surface and the pollutant,and changes in temperature field,stress field,acceleration and displacement are generated,so that the pollutant can be removed.In addition,the comparative analysis of orthogonal experiment and process experiment results showed that under the optimal process parameters of 172W,17KHz,5787rad·min-1and 5.7m·h-1,laser cleaning could effectively remove the pollutants on the substrate surface,improve the surface gloss,and generate no thermal damage.Finally,the surface performance test showed that the surface corrosion resistance was improved after cleaning,and the surface hardness basically tended to the original substrate hardness. |
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