低温冷却工具电极电火花加工研究

Research on Electrical Discharge Machining with Low Temperature Cooling Tool Electrode

以高温镍基合金Inconel718为加工材料,利用液氮蒸发气与空气混合形成低温冷却气体对电火花工具电极进行冷却,以降低电火花工具损耗。以冷却温度为变量进行电火花加工研究。利用粗糙度测量仪TR200和扫描电镜Quanta250对工件表面粗糙度和表面形貌进行分析。结果表明:当脉冲作用时间较短时(脉冲宽度90μs),在相同电参数下,低温冷却电火花加工可降低加工工件的表面粗糙度,在0℃时的表面粗糙度最低,比普通电火花加工的低3.7%~9.5%;随着冷却温度的降低,表面粗糙度会有所增加。电极损耗随着冷却温度的降低而降低,冷却温度在-60℃时的电极损耗比0℃的降低了40%以上。当电参数较小时,低温冷却电火花加工后的工件表面形成微裂纹且裂纹密度随冷却温度的降低而增加。在一定参数下,低温冷却工具电极对降低工件表面粗糙度和工具电极损耗效果显著,某些情况下可能会增加表面的微裂纹。

Taking nickel-based alloy Inconel 718 as processing material,the electric spark tool electrode was cooled by using mixed liquid nitrogen vaporization and air as low-temperature cooling gas to reduce the loss of electric spark tool.The electrical discharge machining(EDM)was carried out by taking cooling temperature as variable.The surface roughness and surface morphology of the workpiece were studied by using roughness measuring instrument TR200 and scanning electron microscope Quanta250.The results show that the when the pulse duration is short(the pulse width is 90 s),under the same electrical parameters,the low temperature cooling EDM can reduce the surface roughness of machining,the surface roughness is the lowest when the temperature is 0℃,which is 3.7%-9.5%lower than that of the ordinary EDM.With the decrease of cooling temperature,the surface roughness increases.The electrode loss decreases with the decrease of the cooling temperature.When the cooling temperature is-60℃,the electrode loss decreases by more than 40%compared with that at 0℃.When the electrical parameters are lower,the micro crack appears on the workpiece surface after low temperature cooling,processing and the crack density increases with the decrease of cooling temperature.Under certain parameters,low temperature cooling tool electrode has a significant effect on reducing wokepiece surface roughness and tool electrode loss,and it can increase surface microcracks in some cases.