臺灣博碩士論文加值系統

製造過程積熱常導致機台結構變形，對於精密加工機台而言，熱變形常是極其重要卻又難以處理的因素。因此本研究開發膨脹係數小於4.5×10-6/℃之延性球墨鑄鐵合金，探討其傳統車削與非傳統的放電加工性能，並選定線切割放電加工機之關鍵下伸臂結構件做為應用範例，以說明降低因線切割加工區積熱而致結構變形與加工精度誤差的應用效益。本文報告經實驗設計與分析之主要成果如下：
(a) 採用鎳及鈷合金的調配可大幅降低墨鑄鑄鐵的熱膨脹係數，其中以32%鎳加上6%的鈷可使鑄鐵達到較佳的性質，其膨脹係數可達4×10-6/℃至5×10-6/℃之間。然而基於強度的要求，需要較高強度要求者應採低膨脹球墨鑄鐵(其抗拉強度大於120MPa以上)，而對於較低強度及較佳制震能需求時，另可採用低膨脹灰口鑄鐵。
(b) 低膨脹合金成形後再施以適當的熱處理可進一步降低其膨脹係數，其幅度可達1×10-6/℃，而本研究提出優化的膨脹係數可降至3.85×10-6/℃。
(c) 在相同車削條件下，其總切削力低熱膨脹鑄鐵＜SUS 304不銹鋼；而表面粗糙度則SUS 304不銹鋼＜低熱膨脹鑄鐵。代表所提出的低熱膨脹鑄鐵易於車削加工，但因切斷點常為石墨基地，使其表面粗糙度略遜於304不銹鋼。
(d) 非傳統加工性方面因其具良好電性，已證實易於放電加工。使用粗加工雕模放電參數其表面粗糙度(Ra)為11.7μm，細加工可達4.55μm。而在線切割放電加工粗能量參數下，低熱膨脹鑄鐵材的輪廓精度比304不鏽鋼稍差。
(e) 對於採用低膨脹鑄鐵之線切割機下伸臂而言，其溫度變異所造成的精度誤差範圍在2μm以內，較目前常用的鋼材之5μm而言，證實可藉改善下伸臂熱變形達60%，提昇精密加工設備的結構穩定度與加工精度。
關鍵字：熱膨脹係數、機械性質、低熱膨脹鑄鐵、線切割放電加工、加工性

Most of the thermal which caused the mechanical deformation of the machine are happened during production process. For accuracy of machine tool, the thermal deformation issue is quite important and difficult to be solved. Therefore, this research is to develop the ductile cast iron alloy whose expansion coefficient is less than 4.5 × 10-6 / ℃. To investigate the traditional turning/machining process and nontraditional EDM process characteristic, and choose overhanging structure of wire Electrical Discharging Machine to be the application example to describe the application effectiveness of reducing the thermal deformation which caused by wire EDM machining area and the accuracy bias of the machining. The survey of machining performance and machinability is based on the experiment design and analysis results, which are list as followed:
(a) The application of Nickel and cobalt alloy can decrease the expansion coefficient of the ductile cast iron. The optimal ration of Nickel and Cobalt Alloy is 32% nickel and 6% cobalt alloy, and this ratio make the cast iron to get better characteristic. The expansion coefficient can be reached between from 4×10-6/℃ to 5×10-6/℃. Due to the requirement of the strength, the cast iron strength requirement is higher, the material should use low expansion ductile cast iron (the tensile strength is over 120Mpa.) If the strength requirement is lower, it should use gray casting iron.
(b) To low expansion alloy, the proper heat treatment can decrease the expansion coefficient after the product is formed. The decrease range can be 1×10-6/℃. In this survey, it’s figured out the optimal expansion coefficient can decrease to 3.85×10-6/℃.
(c) Turning in the same conditions, the total cutting force of low thermal expansion cast iron is less than that of SUS 304 stainless steel; while the surface roughness of the SUS 304 stainless steel is less than low thermal expansion cast iron. For low thermal expansion cast iron, on behalf of the graphite base occur at the cut-off point of turning easy, so that the surface roughness is slightly inferior to SUS 304.
(d) In the aspect of nontraditional machining process, it’s easier to process EDM processes, because of well characteristic of electrical conductivity. By using rough machining condition of EDM, the roughness is around 2.95μm (Ra) and the finish machining can reach 1.13μm (Ra). For the contour accuracy of wire electricity discharge machining, SU304 Stainless is better than that of low expansion cast iron.
(e) To the extend arm of wire EDM machine which is made from low expansion cast iron, comparing with 5μm of accuracy tolerance by the usual stainless steel, that of the low expansion cast iron which is affected and can be reduced into 2μm. It’s approved the material application can increase the stability and accuracy of high precious equipment and improve deformation of the extend arm of wire EDM by 60%.
Keywords: thermal expansion coefficient, mechanical properties, low thermal expansion cast iron, wire EDM, machining performance, machinability

目錄
摘 要 I
Abstract III
誌謝 V
目錄 VI
圖目錄 IX
表目錄 XI
第一章 緒論 1
1.1前言 1
第二章 低熱熱膨脹鑄鐵原理與發展歷程 3
2.1 鑄鐵 3
2.1.1平衡相圖 3
2.1.2碳含量 5
2.1.3石墨 7
2.2合金元素對球墨鑄鐵的影響 9
2.2.1矽元素 9
2.2.2鉬元素 11
2.3影響碳化物形成的因素 13
2.3.1鑄件冷卻速率 13
2.3.2凝固與偏析 13
2.4低熱膨脹鑄鐵 14
2.4.1低熱膨脹現象之原因 14
2.4.2 低熱膨脹鑄鐵的基地組織 18
2.4.3 低熱膨脹鑄鐵的石墨組織 18
2.5放電加工與線切割放電加工原理 19
2.5.1放電加工原理 19
2.5.2放電加工材料去除機制 21
2.5.3線切割放電加工原理 23
第三章 實驗規畫與分析 24
3.1實驗流程 24
3.2合金添加設計與材料性質 25
3.2.1 C、Si的影響 25
3.2.2 Ni、Co的影響 25
3.2.3木模設計及熔鑄作業 25
3.2.4金相檢驗 27
3.2.5機械性質測試 27
3.2.5熱膨脹係數量測 27
3.2.6熱處理 28
3.2.7線切割機下伸臂樣品之試鑄 29
3.3低熱膨脹鑄鐵加工性能測試 31
3.3.1放電加工參數設定與方法 31
3.3.2線切割放電加工參數設定與方法 34
.3.3車削加工參數設定與方法 37
第四章 實驗結果與討論 38
4.1球墨鑄鐵合金配比及性質的探討 38
4.2灰口鑄鐵合金配比及性質的探討 47
4.3低熱膨脹鑄鐵的耐蝕性探討 52
4.4熱處理對鑄鐵性質的探討 52
4.5低熱膨脹鑄鐵與304不鏽鋼加工性能評估 54
4.5.1放電加工表面粗糙度評估 54
4.5.2 線切割放電加工轉角精度評估 56
4.5.3 車削加工性能評估 59
4.6材料用於線切割機之下伸臂結構製作 63
4.6.1下伸臂鑄件檢驗及功能測試 67
4.6.2實機測試改善後之精度 69
第五章 結論 71
第六章 未來發展 72
參考文獻 73
簡歷 75

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