Basic Research On Smelting And Solidification Behavior Of Stainless Steel Micro Melting Pool

As a new manufacturing process,the selective laser melting technology has gradually attracted attention from domestic and foreign scholars,applying this process to the field of high nitrogen stainless steel manufacturing can improve the quality and performance of the material,and the molten pool in the process of laser irradiation on powder materials the discussion of heat transfer and flow rules can provide theoretical basis for selective laser melting to produce high nitrogen stainless steel,the article used a variety of laser heat sources with different parameters to irradiate stainless steel powder,and studied the heat transfer mechanism and process of powder melting and solidification,influencing factors of molten pool flow state.The heat transfer simulation calculations show that the different heat source parameters have a great impact on the melting and forming effect of the molten pool,the temperature field and the shape of the molten pool formed by high-power and smalldiameter lasers are narrow and deep,the temperature field and morphology of the molten pool formed by the diameter laser are relatively wide and shallow.In the solidification stage,the time required for the solidification of the molten pool under a high-power heat source is longer,small-diameter lasers dissipate heat faster than solid-formed molten pools with shorter diameters.The simulation calculation of the flow field of the molten pool shows that the fluid in the molten pool under the laser flows in Marangoni circulation,increasing the power and reducing the spot diameter can effectively reduce the center of motion of the fluid and make the circulation reach the depth of the molten pool to better homogenize the molten pool,composition,and can accelerate the melt flow to achieve a better mixing state,but too high power will cause the melt flow to be too violent,which is likely to cause liquid splashes and the formation of material voids in industrial production,reducing the quality of molded parts.As the heating time is extended,the melt movement speed gradually increases and gradually stabilizes,due to the decrease of the temperature gradient between the center and the boundary of the molten pool in the later period of heating,the speed increase is significantly larger than that of the molten pool under the lower-power heat source.The results show that increasing the laser power during the selective laser melting process can promote the melting of the molten pool,and reducing the diameter of the heat source spot can increase the depth of the molten pool and accelerate the solidification of the melt after the heat source disappears,the flow field is disordered,so the laser with 200 W power and 20 μm spot diameter is selected as the heat source,which can improve the production efficiency during the melting process in the selected area and ensure the quality of the molded parts.Figure61;Table6;Reference64.