2. The thickness of the metamorphic layer becomes thicker as the pulse energy increases. Due to the randomness of the spark discharge process, the thickness of the metamorphic layer is often uneven under the same processing conditions. The data of the thickness of the metamorphic layer measured from the relevant test piece indicates that the medium wire cutting electrical standard is abnormal. The layer thickness has a significant effect. For example, the wire is brass wire, the low-speed wire (0.6m/s) processing voltage is 60V, the current is 5.5A, the maximum thickness of the metamorphic layer is 20.0μm, and the average is increased to 13.8μm.
3. The microhardness is obviously reduced, and the microcracks appear due to the change of the metallographic structure and element content of the metamorphic layer, so that the microhardness of the surface of the workpiece is significantly reduced. For example, in a deionized water, a 70 HV drop to 670 HV after wire cutting is performed, and a wire-cut softened layer usually appears at a depth of a few ten microns from the surface. At the same time, the surface metamorphic layer generally has tensile stress and microcracks may occur. Especially when cutting cemented carbide, under the condition of conventional electrical standard parameters, cracks are more likely to occur and voids exist. It is extremely harmful.