Application of large-area electron beam irradiation to micro-edge filleting

Efficient micro-edge filleting with curvature radius from 10 to 100 μm for industrial products is required, since a demand for industrial components with precise and complex shape has been increasing recently. In large-area electron beam (EB) irradiation method, wide area of metal surface can be melted instantly and uniformly. Therefore, highly efficient surface finishing of metal can be performed. In addition, edge of convex part rounds since material removal and/or melting of the edge is preferentially done there due to difficulty of heat diffusion at the edge and concentration of EB. In this study, possibility of micro-edge filleting for workpiece with sharp edge by large-area EB irradiation was investigated. Experimental results show that micro-edge filleting without remarkable shape change of side surface near the edge can be performed under appropriate EB conditions. The curvature radius of edge can be controlled from sharp edge to rounded edge, and ideal curvature radius is obtained. Furthermore, thermo-fluid analysis with considering the concentration of EB to the edge was performed to clarify flow of molten metal and mechanism of edge shape change in the EB irradiation. Edge shape change can be simulated by the thermo-fluid analysis. It was made clear that surface tension is main driving force for edge shape change in large-area EB irradiation.