The thermal conductivity of cemented carbide is relatively small. For example, the thermal conductivity of tungsten drill type cemented carbide is 58.62~87.92W/(m•K), and the thermal conductivity of tungsten-cobalt-titanium alloy is generally 16.75~62.8W/(m• K). In order to avoid cracks, processing standards with a large pulse width cannot be selected. Therefore, in rough machining, relatively small pulse width (for example, less than 100 μs) and high peak current are used, so that the heat-affected layer of EDM is thinner. Even if there is a crack, its depth is relatively shallow. Then, when finishing machining, small pulse width and higher peak current are also selected to remove almost all the shallow cracks produced by rough machining.
Cracks have a great influence on the service life of cold forging dies, so the cold forging dies after finishing EDM must be polished to remove the heat-affected layer produced by EDM, otherwise the die may crack during use.
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