放電加工參數影響鋁合金6061加工特性之研究

Abstract

本研究探討放電加工參數影響鋁合金6061加工特性之研究。以紅銅為電極，固定脈衝時間、休止時間、排渣高度、放電電壓，改變放電電流8 A~15 A，探討放電加工特性包括：電極消耗率、材料移除率、表面粗糙度、變質層厚度、疲勞壽命。為了監控放電加工過程品質處於控制狀態，本研究將最佳放電加工參數重複多次實驗 (35次)，觀察鋁合金 (6061)放電加工特性，配合品質管制圖，達到監控預測的效果。 研究結果顯示，較高的放電電流 (15 A)，有較大的材料移除率，電極消耗率，表面粗糙度及工件表面硬度。此外、增加放電電流，變質層厚度亦隨著增加(由10.31 μm 增加到19.38 μm)，因為變質層硬度遠高於母材，故工件疲勞壽命隨之提升。經多次 (35次)重複放電加工，透過品質管制圖(Shewhart control chart)監控，顯示該放電加工特性始終保持在穩定可監控狀態。 此外，應用電漿蝕刻放電加工件表面，進一步提升放電加工件疲勞壽命。配合田口實驗設計L9 (33)，探討電漿蝕刻參數:蝕刻功率 (W)、氧氣流率 (sccm)、蝕刻時間 (min)對放電加工件表面粗糙度、水滴接觸角、疲勞壽命的影響。以掃描式顯微鏡(SEM)，觀察放電加工件表面形貌及變質層。研究結果顯示，放電加工件經電漿蝕刻，可有效清除工件表面殘渣及微細裂紋，降低微裂紋對工件的不良影響，有效提升放電加工件疲勞壽命約25%。

The study tested electric discharging machining parameters influence the machining characteristics of aluminum alloy 6061. With copper as the electrode, Fixed pulse time, Slag height, discharge voltage, and change discharge current 8 A~15A. To investigate EDM features including electrode consumption rate, material removal rate, surface roughness, recastlayer and fatigue life. In order to monitor the quality of the discharge process in control, the optimal discharge machining parameters repeated experiments (35 times) , observed an aluminum alloy (6061) discharge machining characteristics, with quality control charts, to monitor the predicted effect. The results showed a high discharge current (15A) with a larger material removal rate, electrode consumption rate, surface roughness and surface hardness. In addition, increasing the discharge current, recastlayer thickness also increases (from the 10.31 μm to 19.38 μm), due to affected layer hardness is much higher than the base material, so the fatigue life rise with the workpiece. After repeated (35 times) discharge machining experiments, through quality control charts (Shewhart control chart) monitor the discharge machining characteristics remain in a stable state. Moreover, the application of plasma etching the surface discharge machining, in further, enhance fatigue life of electrical discharge machining parts.,Investigated plasma etch parameters: etching power (W), oxygen flow rate (sccm), etching time (min) for the influence of electrical discharge machining surface roughness, water contact angle and fatigue life. With scanning electron microscope (SEM), observe the surface morphology and recastlayer. The experimental result shows that the EDMed workpiece by plasma etching, remove surface residue and micro-cracks effectively, reducing the adverse effects of micro-cracks, the fatigue life of EDMed workpiece can be improved.