DEVELOPMENT OF HIGH EFFICIENCY SURFACE TREATMENT OF METAL MOLD BYLARGE-AREAELECTRON BEAM IRRADIATION

提出了一种大面积脉冲电子束辐照金属模具光整加工新工艺。这里使用的大面积电子束辐照设备是最近开发的用于表面处理或表面改性的设备。具有高能量密度的电子束可以在不集中束的情况下照射。然后，可以使用最大直径为60mm的大面积电子束来熔化或蒸发金属表面。实验结果表明：（1）在适当的电子束辐照条件下，艾德Med金属型表面经大面积电子束辐照后，表面粗糙度可在几分钟内从6μmRz降至0.7μm。而且，光泽度可以得到很好的改善。(2)在金属模具上形成很薄的再凝固层。再凝固层的结构不同于基材的结构，其中晶粒尺寸通过大面积EB照射而变小。(3)在这种方法中，通过将EB集中到凸部上来进行表面平滑。(4)大面积电子束辐照可以提高金属模具表面的耐蚀性和排斥性，同时使表面光滑，但表面硬度略有下降。(5)即使表面的倾斜角接近90度，表面粗糙度也可以得到很好的改善，这表明在由相对小的倾斜表面组成的小的简单形状的模具的情况下，可以在几分钟内使整个表面平滑而无需移动和倾斜模具。(6)在电子束辐照表面上去除的材料的厚度非常小并且几乎恒定，这使得可以精确地完成金属模具表面。

A new finishing process for metal molds by large-area pulsed electron beam irradiation is proposed. The large-area electron beam irradiation equipment used here was recently developed for surface treatment or surface modification. Electron beam with high energy density can be irradiated without concentrating the beam. Then, large-area electron beam with a maximum diameter of 60mm can be used for melting or evaporating metal surface. Using this system, the possibility for high efficient finishing of metal molds is experimentally discussed.Main conclusions obtained are as follows;(1) Under a proper EB irradiating condition, the surface roughness of ED Med metal mold surface can be reduced from 6μmRz to 0.7μm in just a few minutes by large-area EB irradiation. Also, the glossiness can be improved very well.(2) Very thin resolidified layer is formed on metal mold. The structure of the resolidified layer differs from that of the base material, in which the grain size becomes smaller by large-area EB irradiation.(3) Surface smoothing is performed by concentrating EB onto convex parts in this method.(4) The corrosion resistance and the repellency of metal mold surface can be improved by large-area EB irradiation, simultaneously with surface smoothing, whereas the surface hardness a little decreases.(5) Even if the tilting angle of surface is close to 90 degrees, the surface roughness could be improved very well, which indicates that in the case of small simple shaped mold consisting of relatively small tilting surfaces, the smoothing of the whole surface is possible in a few minutes without moving and tilting the mold.(6) The thickness of removed material on the EB irradiated surface is very small and almost constant, which make it possible to finish the metal mold surface precisely.