高張力鋼材微孔放電加工表面特性之研究

Study on Surface Characteristics of Micro-Hole EDM for High Tensile Steel Material

謝作生(Tso-Sheng Hsieh)

指導教授 ： 于劍平

崑山科技大學/工程學院/機械工程研究所/碩士(2007年)

摘要

微孔放電加工之表面加工精度要求較一般放電加工嚴苛，加工參數之配置即相對重要，因加工參數配置不當，將使微孔放電加工之銅線電極產生熔融現象，並導致加工表面形成變質層，對工件造成不良影響，而需藉由後續處理去除。本論文係以HY80高張力鋼材進行微孔放電加工，並對加工後之材料移除率、電極消枆比、擴孔量、表面粗糙度、變質層厚度進行研究。 本研究以田口方法，選用放電電流（Ip）、放電持續時間（TON）、放電休止時間（TOFF）及間隙電壓（Vg）作為微孔放電加工參數，探討加工特性品質，包含材料移除率、電極消耗比、擴孔量、表面粗糙度、變質層厚度等最佳微孔放電加工參數組合，並以最佳加工參數組合進行驗證實驗。再以單因素實驗法，探討單一放電條件與加工特性品質之關係，並藉由加工參數之改變，利用掃描式電子顯微鏡觀測HY80母材經由微孔放電後之進口段、中段及出口段表面形貌之變化，同時觀察放電痕分佈密度、直徑、深度、積屑情形及表面裂縫型態…等。 由本實驗分析得知，影響材料移除率之主要參數為放電電流，次為放電持續時間；影響電極消耗比之主要參數為放電持續時間，次為放電電流；影響擴孔量之主要影響參數則為間隙電壓，次為放電電流；而對另對表面粗糙度之主要影響參數則為放電持續時間，次為間隙電壓；另對變質層厚度之主要影響參數則為放電持續時間，次為放電電流。於單因素實驗分析得知，材料移除率、擴孔量與表面粗糙度將因放電電流與放電持續時間增加而增加。經由本研究深入之實驗與利用田口及單因素實驗法相互驗證及分析探討，對高張力鋼材經微孔放電加工後之特性做一完整研究，同時可將研究成果提供業界參考。

關鍵字

田口方法 ； 材料移除率 ； 電極消耗比 ； 擴孔量 ； 表面粗糙度 ； 變質層厚度 ； 微孔放電加工

並列摘要

The precision demand of surface machining for micro-hole EDM was more serious than common EDM. It is very important to layout the machining parameters. If the machining parameters layout and setup improperly, the copper electrode of micro-hole EDM will be melted and induced the larger surface roughness and thicker transformation layer which were not good for workpiece. And then the rough surface and poor transformation layer must be removed with second machining process. In this investigation, the HY80 high tensile steel material was employed to workpiece and then precedes the machining process of micro-hole EDM. After micro-hole EDM, the material remove rate（MRR）, electrode remove ratio（ERR）, and hole enlargement（HR）,and surface roughness（SR） were analyzed,the thickness of the transformation layer（TTL）.
In this study, we use Taguchi method to find main influencing factors. The pulse current（Ip）, pulse-on duration（TON）, pulse-off duration （TOFF）, and gap voltage（Vg） will be selected as machining parameters of micro-hole EDM. Investigating the machining characteristics, involve material remove rate（MRR）, electrode remove ratio（ERR）, hole enlargement（HR）, and surface roughness（SR） ,the thickness of the transformation layer（TTL）, the optimal combination of parameters was obtained. And then confirmation experiment was done by the optimal combination of parameters. On the other hand, the single-factor experimental method was used to investigate the relation of EDM conditions and machining characteristics, and the surface characteristic of HY80 high tensile steel after micro-hole EDM.
And to confer the material surface characteristic after machining by the difference machining parameters, and observe meta-micro-hole electrical discharge with scanning electron microscope. The observation items have the conformation of electrical-discharge, distributive thickness, diameter and depth of the crater, condition of amass tailing, cleavage conformation of surface and distributive thickness, etc.
By the analysis of the experiment we find pulse current （Ip） are the primary influencing parameters for the material remove rate, the secondary parameters are pulse-on duration（TON）. The primary influencing parameters for the relative electrode wear ratio are pulse-on duration （TON）, the secondary parameters are the pulse current（Ip） The primary influencing parameters for the hole enlargement are gap voltage （Vg）, the secondary parameters are the pulse current. The primary influencing parameters for the surface roughness are pulse-on duration（TON）, the secondary parameters are gap voltage （Vg）. The primary influencing parameters for the thickness of the transformation layer are pulse-on duration（TON）, the secondary parameters are the pulse current（Ip）. From the single-factor experiment shows the material removal rate, the hole enlargement and the surface roughness increase as the pulse current （Ip） and pulse-on duration （TON） increase. By the deviation analysis of the study by Taguchi method and sing factor experiment method, we can understand in depth of machining property of high tensile steel material after micro-hole EDM .And the study result can provide the consultation to the affiliated industry while machining.

並列關鍵字

material removal rate ； electrode wear ratio ； hole enlargement ； surface roughness ； the thickness of the transformation layer. ； Taguchi method ； micro-hole EDM

參考文獻

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