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在不同脉冲电流条件下对模具钢P20进行电火花成形加工,研究了脉冲电流对试样表层的微观组织结构的影响,以及微观组织结构对表面性能的影响。结果表明,电火花成形加工后试样的表面分为烧蚀层、熔化凝固层和热影响层。随着脉冲电流的增大,熔化凝固层和热影响层的厚度增大;在加工过程中元素的扩散和迁移使熔化凝固层外侧碳元素和氧元素的浓度较高。电火花成形加工过程相当于热处理过程,从熔化凝固层到热影响层、基体,显微硬度快速降低。有限元模拟计算表明,在熔化凝固层内的垂直与界面微裂纹主要是加工放热过程中的残余应力引起的。
The effects of pulse current on the microstructure of the sample surface and the effect of microstructure on the surface properties were studied by EDM of P20 steel under different pulse currents. The results show that the surface of the sample after EDM is divided into ablation layer, solidified layer and heat affected layer. As the pulse current increases, the thickness of the solidified layer and the heat affected layer increase. The diffusion and migration of the elements in the process lead to a higher concentration of carbon and oxygen outside the solidified layer. EDM process is equivalent to the heat treatment process, from the solidified layer to the heat affected layer, the matrix, the rapid decrease in microhardness. Finite element simulation shows that the vertical and interfacial microcracks in the melt-solidified layer are mainly caused by the residual stress in the process of exothermic process.