| 摘要: | 本研究是利用超音波輔助放電加工模具鋼SKD61，同時在放電液體中添加電阻值遠低於放電液的碳化矽粉末，發展創新之放電加工方法，以獲得精密加工成型之技術，並改善放電加工後之表面粗糙度及增進加工之穩定性，研究中探討各種放電加工參數，例如：碳化矽粉末濃度、峰值電流、放電週期時間、超音波功率等對於加工模具鋼SKD61之各種加工特性影響，加工特性包含表面粗糙度與加工時間，並利用雷射共軛焦表面形貌量測儀(LSCM)與電子掃描顯微鏡(SEM)作表面微結構和加工區變質層觀察。
實驗結果顯示，放電加工時加入超音波輔助，可使介電液能有效循環，加工熱與放電渣能加速離開加工區域，可提升加工效率、縮短加工時間。此外，於介電液中加入碳化矽粉末，可藉由之適當濃度碳化矽溶液增加介電液的導電度，使架橋效應更顯著，並使加工品質能夠提升。於本研究依序進行單因子實驗後，當參數為放電液濃度5×10-3 wt.%、峰值電流0.8 A、放電週期時間300 ?s、超音波功率4段時，可得到本實驗之最佳表面粗糙度值0.684 ?mRa，與不加碳化矽的去離子水介電液的表面粗糙度1.300 ?mRa相比較，加工後的表面粗糙度Ra值下降了47%，且加工時間亦為較短，以及可獲得較為薄化之再鑄層。
;This research is using ultrasonic-assisted electric discharge machining mold steel SKD61, and add silicon carbide powder whose resistance value is much lower than most of the electric discharge liquid to develop innovative electric discharge machining methods to replace the precision machining molding technology and improve the after-discharge machining,the surface roughness and the stability of processing, various electrical discharge machining parameters under study, such as: discharge liquid concentration, incident current, discharge cycle, ultrasonic power, etc., which affect the various processing characteristics of processing mold steel SKD61.The processing characteristics include the surface Roughness and processing time. And use the laser conjugate focal length surface topography measuring instrument (LSCM) and scanning electron microscope (SEM) to observe the surface microstructure and the processing area metamorphic layer.
The experimental results show that the addition of ultrasonic assistance during electrical discharge machining can effectively circulate the dielectric fluid. Also, the processing heat and electrical discharge slag can accelerate to leave the processing area, which can improve processing efficiency and shorten processing time.In addition, adding silicon carbide powder to the dielectric fluid can increase the conductivity of the dielectric fluid due to the proper concentration of silicon carbide solution, making the bridging effect more significant and improving the processing quality.In this study, single-factor experiments were performed sequentially, the result show that when the parameters are the concentration of discharge fluid 5×10-3 wt.%, peak current 0.8A, discharge cycle time 300?s, and ultrasonic power 4 segments, the best surface roughness 0.684 ?mRa can be obtained. Compared with the surface roughness of 1.300 ?mRa of the deionized water dielectric fluid without silicon carbide, the surface roughness Ra value after processing is reduced by 47%, accompanied by shorter processing time and a thinner recasting layer. |
