| 摘要: | 電化學加工，屬於非傳統加工方法的一種，以電解現象達成加工成形之目的，其優點為加工不受材料硬度限制、刀具不易耗損、工件表面無應力殘留、工件表面粗糙度佳。其機台設備構造相對簡單，造價較低，加工速度快，複雜外形的工件也能輕易加工。
碳化鎢（Tungsten Carbide）合金為高硬度合金，常用於製作切削刀具及模具，然而，若使用常見的硝酸鈉（NaNO3）為做為電解液進行電化學加工，卻會產生鈍化層（passivation layer），使陽極的材料移除率大幅降低。本研究之目的在於，使用氨水（NH4OH）與硝酸鈉之複合溶液，做為電解液進行加工，探討操作電壓、硝酸鈉溶液濃度、氨水溶液濃度、陽極工件圓棒轉速、加工時間以上五者對材料移除率與工件外形之影響。
實驗結果顯示，在加工電壓20 V、氨水溶液濃度4 M、陽極工件圓棒轉速3000 rpm的條件之下，若硝酸鈉濃度為2 M或4 M，將有最大的材料移除率。此時，若硝酸鈉濃度為2 M，陽極工件圓棒外形為正錐狀；若硝酸鈉濃度為4 M，陽極工件圓棒外形為倒錐狀，且表面具有塊狀不平整。加工後工件表面抛光度會微幅下降，但不會消失。陽極工件圓棒轉速為3000 rpm時，與靜止或低轉速相比，具有較大的材料移除率與較接近圓柱之外形。加工時間只能控制材料移除量，無法修正工件外形。
;Electrochemical machining (ECM) is one of the non-traditional manufacturing process, shaping workpiece by electrolysis. The advantages are that the process is independent of material properties, little or no tool wearing, no surface stress, and good surface finishing. The machining equipment is relatively simple and inexpensive with fast processing speed, and capable of complex workpiece geometry.
Tungsten carbide (WC) alloy has high stiffness and high surface hardness, commonly used in cutting tools and mold. But in ECM, passivation layer will be generated in sodium nitrate (NaNO3) electrolyte, and significantly reduce the material removal rate (MRR) in anode. The object of this study was to take sodium nitrate and ammonia hydroxide (NH4OH) as hybrid electrolyte in ECM process, and investigate the effects of various processing parameters (e.g. applied voltage, NaNO3 concentration, NH4OH concentration, electrode rotation speed, and machining time) on MRR and electrode shape.
The results show that, with condition of 20 V, 4 M NH4OH and 3000 rpm, there will be largest MRR. Meanwhile, the shape of electrode will be tapered if NaNO3 is 2 M, and reversely tapered with uneven surface if NaNO3 is 4 M. Surface quality will slightly degrade after machining. Machining time can control MRR rather than electrode shape. |
