放電加工參數對HY-80高降伏鋼加工特性之研究

Study on Characteristics of EDM Effect for HY-80 Material Machining Parameters

曹智韜(Chih-Tao Tsao)

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(2011年)

摘要

本研究主要係選用HY－80高降伏鋼作為實驗母材，藉由四軸CNC雕模放電加工機，經調變電氣參數，亦即改變放電電流（IP）、放電持續時間（TON）及放電休止時間（TOFF），以單因素實驗法，探討單一放電條件、加工特性與品質之關係，並利用掃描式電子顯微鏡據以觀察HY－80高降伏鋼於不同之放電環境下，其表面形貌之變化。
實驗首先完成電極及工件材料之選取及實驗參數設定，再將試片及電極分別裁切、研磨、清洗及重量量測後，進行放電加工，並在完成後量測加工特性與表面形貌觀察。
實驗結果顯示當放電持續時間及放電休止時間設為固定參數時，放電電流由3A分段調升至25A，其材料移除率及電極消耗率隨放電電流增加而增大。當固定放電電流及放電休止時間時，放電持續時間於10∼20μs之間因放電持續時間增長，單位時間內放電次數增加，材料移除率亦相對增加，然放電持續時間大於20μs時，材料移除率逐漸下降後趨於定值，另放電持續時間介於10∼100μs時，時間愈長則電極消耗率愈小，大於100μs時電極消耗率變化有減緩之趨勢。當實驗設定放電電流及放電持續時間為固定參數時，放電休止時間增加，單位時間內之放電次數相對減少，故加工速度與電極消耗率自然亦隨著降低。
放電參數條件改變與表面粗糙度之相對應關係可由實驗分析得知，當放電電流增加，表面粗糙度亦隨之增加；而改變並增加放電持續時間或放電休止時間，表面粗糙度反呈現反比之趨勢。
另於表面形貌觀察放電痕時，可明顯發現當放電電流增加將使放電痕逐漸變深、變大，密度則會降低，堆疊情形逐漸轉變為鬆散；隨著放電持續時間增加，放電痕面積隨之增大，淺坑與痘瘡高度則變淺；在表面裂紋之觀察發現當加工電流較低時，裂紋數量較少，且特徵形貌皆屬輻射狀裂紋，隨著放電電流增加，裂紋更為稀少，然當放電電流提升至20A以上時，工件表面裂紋將隨放電電流增加而增加；放電持續時間愈長，裂紋密度、寬度、長度隨之增加，並呈現出樹枝狀之裂紋。
本研究另進行正向與側向放電加工實驗，於相同之實驗參數下，發現正向放電所形成之球狀附著物明顯較側向放電為少，且側向放電所形成之類毛線球狀附著物並未於正向放電之試件中出現，推論應係放電過程中之急熱驟冷型態不同所致。

關鍵字

雕模放電加工 ； 單因素實驗法

並列摘要

In this study, we use HY-80 workpiece to find characteristics, by 4D CNC EDM, pulse count current(Ip), pulse-on duration(TON), pulse-off duration (TOFF), and gap voltage(Vg) will be selected 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.
By the analysis of the experiment, the single-factor experimental method was used to investigate the relation of EDM conditions and machining characteristics, and the surface characteristic of HY-80 high tensile steel after EDM.
The experimental result discharges when the time of stopping is set as the regular parameter, discharge electric current is rise to 25A to transfer by stage from 3A, consume discharge electric current increase at the same time. As discharge in the electric current to stop regularly in time, and increase between 10∼20μs, the material is moved except that the rate also increases relatively, but discharge in duration when being greater than 20μs, the material is moved except value after the rate drops gradually, discharge duration at lying between 10∼100μs, long electrode consuming rate few time have separately, the change of consuming rate of the electrode has trend slowed down when being greater than 100μs. When it is regular parameters that the experiment establishes and discharges the electric current, it’s stop time increase to discharge, unit relative to reduce to discharge number of times, so processing speed and the consuming rate of electrode, also with reduce naturally.
By experimental analysis, relation of EDM parameter terms can be learnt with phase corresponding , surface of roughness to change, increase pulse count current, the roughness of surface also increases ; And change pulse count current or pulse-off duration to increase, surface roughness appear inverse ratio trend their instead.
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 increase 20A, distributive thickness, diameter and depth of the crater, condition of amass tailing, cleavage conformation of surface and distributive thickness.
In study, same experimental EDM parameter researching for main-side and other side, find out method was used to investigate the relation of EDM conditions and machining characteristics, and infester balloter didn’t flat on main-side workpiece, potation for different method faster increase hot-cold change in relation of EDM conditions.

並列關鍵字

Die Sinking EDM ； single-factor experimental method

參考文獻

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