曲面葉片的數(shù)控加工工藝設(shè)計及CAM編程仿真含NX三維及CAD圖
曲面葉片的數(shù)控加工工藝設(shè)計及CAM編程仿真含NX三維及CAD圖,曲面,葉片,數(shù)控,加工,工藝,設(shè)計,cam,編程,仿真,nx,三維,cad
設(shè)計（論文）任務(wù)書
題 目
三維CAD與CAM技術(shù)在數(shù)控加工中的應(yīng)用—典型汽車零部件的CAM編程（曲面）
姓 名
學(xué) 號
題目類型
工程實(shí)際
科 研
實(shí)驗(yàn)室建設(shè)
其 它
一、課題主要研究（設(shè)計）內(nèi)容：
1. 學(xué)習(xí)數(shù)控加工技術(shù)，了解數(shù)控加工的技術(shù)特點(diǎn)，分析典型汽車零件的特點(diǎn)
2. 學(xué)習(xí)UG 或Mastercam軟件，掌握計算機(jī)編程技巧
3. 依據(jù)典型汽車零件的技術(shù)要求及加工要求制定加工方案；
4． 實(shí)現(xiàn)UG或Mastercam環(huán)境下的建立典型零件的三維建模和數(shù)控加工動作的運(yùn)動仿真。
5. 編寫加工程序，對比加工參數(shù)設(shè)定重要性及選擇性，并對加工效果及加工方案進(jìn)行分析及評價
二、工作進(jìn)度要求（分階段提出具體時間要求）：
2013.10.08——2013.11.30 收集相關(guān)資料，確定畢業(yè)設(shè)計課題
2013.12.01——2013.12.17 學(xué)生完成課題研究與設(shè)計方案論證報告交給指導(dǎo)教師，完成課題開題報告
2013.12.18——2014.01.31 學(xué)習(xí)UG或Mastercam三維軟件并完成典型零件加工方案確定
2014.02.01——2014.03.10 實(shí)現(xiàn)UG或Mastercam環(huán)境下典型零件的運(yùn)動仿真，并完成相關(guān)典型零件的制作數(shù)控加工加工程序編制，完成中期報告
2014.03.11——2014.04.15 進(jìn)行0號裝配圖紙繪制及論文撰寫等工作
2014.04.16——2014.04.25 完成論文撰寫及各類圖紙繪制、各數(shù)控程序的匯總及必要表格的歸納，并提交給指導(dǎo)老師
2014.04.26——2014.05.09 指導(dǎo)教師評閱畢業(yè)論文，學(xué)生及時積極修改指導(dǎo)老師指出的問題，準(zhǔn)備畢業(yè)設(shè)計答辯內(nèi)容
2014.05.10——2014.05.16 完成答辯
三、應(yīng)查閱的主要參考文獻(xiàn)：
[1] 閻紅娟《數(shù)控自動編程參數(shù)設(shè)置技巧》化學(xué)工業(yè)出版社
[2] PeterSmid《數(shù)控編程手冊(原著第3版)》化學(xué)工業(yè)出版社
[3] 尚廣慶《數(shù)控加工工藝及編程》上海交通大學(xué)出版社
[4] PeterSmid《數(shù)控編程技術(shù):高效編程方法和應(yīng)用指南》化學(xué)工業(yè)出版社
[5] 顧雪艷《數(shù)控加工編程操作技巧與禁忌》機(jī)械工業(yè)出版社
四、畢業(yè)設(shè)計（論文）預(yù)期成果或結(jié)論性觀點(diǎn)
1. 一份畢業(yè)論文；
2. 一份學(xué)生手冊；
3. CAD三維模型，CAM加工程序，切削仿真動畫（可折合成1張A0圖紙內(nèi)容工作量）
4. A0號圖紙1份。
五、畢業(yè)設(shè)計（論文）完成提交方式（設(shè)計、作品照片、實(shí)物、模型、技術(shù)文檔或論文、含有技術(shù)文檔或論文的光盤等）
1、以電子稿形式上交所有畢業(yè)成果要求的內(nèi)容。
2、文字編排的成果（包括畢業(yè)論文與各種報告等）需在電子稿的情況以外附加打印稿。
指導(dǎo)教師： 審核人：
年 月 日 年 月 日
畢業(yè)設(shè)計（論文）開題報告
題 目
三維CAD與CAM技術(shù)在數(shù)控加工中的應(yīng)用—典型汽車零部件的CAM編程（曲面）
姓 名
學(xué) 號
一、本課題的研究目的和意義
1．目的：對典型汽車零部件特點(diǎn)進(jìn)行分析；掌握計算機(jī)三維建模和計算機(jī)編程；熟悉加工方案的制定和評價；學(xué)會對加工方案進(jìn)行分析；
2．意義：對制造業(yè)來說，CAD/CAM是提高產(chǎn)品設(shè)計品質(zhì)和制造品質(zhì)、縮短產(chǎn)品開發(fā)周期，降低產(chǎn)品開發(fā)成本的強(qiáng)有力手段，已成為企業(yè)贏得市場的制勝法寶。因此，研究我國機(jī)械行業(yè)CAD/CAM技術(shù)應(yīng)用現(xiàn)狀，對加快我國機(jī)械行業(yè)CAD/CAM技術(shù)推廣應(yīng)用步伐，提高我國機(jī)械制造業(yè)的國際競爭力具有深遠(yuǎn)的意義。通過對汽車零部件的CAM編程，可以讓我更好地了解現(xiàn)代計算機(jī)輔助設(shè)計。搜集整合相關(guān)資料時，使我對國內(nèi)外CAD/CAM有了一定的了解，同時開闊了自身的視野。與老師同學(xué)們討論，不但增強(qiáng)我的專業(yè)知識水平，也很大程度上提高了我的語言表達(dá)溝通能力。總之，此次畢業(yè)設(shè)計將整合我大學(xué)四年中所學(xué)到的各項(xiàng)專業(yè)知識，理論聯(lián)系實(shí)際。讓我的自身綜合能力得到很大的提升。
二、本課題的主要研究內(nèi)容（提綱）
1. 學(xué)習(xí)數(shù)控加工技術(shù)，了解數(shù)控加工的技術(shù)特點(diǎn)，分析典型汽車零件的特點(diǎn)
2. 學(xué)習(xí)UG 或Mastercam軟件，掌握計算機(jī)編程技巧
3. 依據(jù)典型汽車零件的技術(shù)要求及加工要求制定加工方案（重點(diǎn)在自動加工參數(shù)、刀路路線選擇等方面）；
4. 實(shí)現(xiàn)UG或Mastercam環(huán)境下的建立典型零件的三維建模和數(shù)控加工動作的運(yùn)動仿真。
5. 編寫加工程序，對比加工參數(shù)設(shè)定重要性及選擇性，并對加工效果及加工方案進(jìn)行分析及評價
6. 3000字符的科技英文資料翻譯。
三、文獻(xiàn)綜述（國內(nèi)外研究情況及其發(fā)展）
CAD/CAM技術(shù)在20世紀(jì)60年代逐漸興起，經(jīng)過數(shù)十年的發(fā)展，先后經(jīng)過了四個年代，分別為大型機(jī)、小型機(jī)、工作站、微機(jī)時代。現(xiàn)如今，CAD/CAM軟件在工作站和微機(jī)平臺已經(jīng)占據(jù)主導(dǎo)地位。
在我國有許多流行的商品化軟件。比如 PICAD，軟件具有參數(shù)化和較強(qiáng)的開放性，對特征點(diǎn)和特征坐標(biāo)可自動捕捉及動態(tài)導(dǎo)航;系統(tǒng)提供交互環(huán)境下的開放的二次開發(fā)工具，用戶可以增加功能或開發(fā)專業(yè)應(yīng)用軟件。再比如CAXA：CAXA電子圖板足高效，方便、智能化的通用中文設(shè)計繪圖軟件，輔助設(shè)計人員進(jìn)行零件圖、裝配圖、工藝圖表、平面包裝的設(shè)計，適合二維繪圖的場合，可使設(shè)計人員甩掉圖板，滿足相關(guān)行業(yè)的設(shè)計要求。還有金銀花系統(tǒng)(Lonicera)、高華CAD，GS-CAD98、開目CAD等軟件，其中的金銀花系統(tǒng)的目標(biāo)是向國外三維CAD軟件發(fā)出強(qiáng)有力的挑戰(zhàn)。但我國CAD/CAM相比國外的軟件有如下缺點(diǎn)：應(yīng)用范圍窄、層次淺；功能單一，經(jīng)濟(jì)效益并不明顯。
在國外，UG 、PROE、solidworks是CAD/CAM軟件的佼佼者，?Unigraphic(UG)：UG是源于美國麥道(MD)公司的產(chǎn)品，是由美國通用汽車公司EDS分部的獨(dú)立子公司UnigraphicSolutions開發(fā)的，集CAD/CAM/CAE于一體的 機(jī)械工程輔助系統(tǒng)，適用于航空、航天、汽車、通用機(jī)械及模具等的設(shè)計、分析及制造工程。UG是將優(yōu)越的參數(shù)化和變量化技術(shù)與傳統(tǒng)的實(shí)體、線框、表面功能結(jié)合在一起，還提供了二次開發(fā)工具GIRP、UFUNG、ITK，允許用戶擴(kuò)展UG的功能。(2)AutoCAD：它是美國Autodesk公司開發(fā)的具有交互式和強(qiáng)大二維功能的繪圖軟件(如二維繪圖、編輯、剖面線和圖案繪制、尺寸標(biāo)注以及二次開發(fā)等功能)，并有部分三維功能。AutoCAD軟件是目前世界上應(yīng)用最廣的CAD軟件，占整個CAD/CAE/CAM軟件市場的37%左右(在中國二維繪圖CAD軟件市場占有絕對優(yōu)勢)。(3)Pro/Engineer：它是美國參數(shù)技術(shù)公司(PTC)1988年的產(chǎn)品，具有先進(jìn)的參數(shù)化設(shè)計、基于特征設(shè)計的實(shí)體造型和便于移植設(shè)計思想的特點(diǎn)，用戶界面友好，符合工程技術(shù)人員的機(jī)械設(shè)計思想，能將整個設(shè)計和生產(chǎn)過程集成在一起。最近幾年P(guān)ro/E已成為三維機(jī)械設(shè)計領(lǐng)域里最富有魅力的軟件，在中國模具工廠得到了非常廣泛的應(yīng)用。(4)由美國Autodesk公司基于參數(shù)化特征實(shí)體造型和曲面造型而開發(fā)的MDT軟件。由美國SolidWorks公司基于Windows，平臺的全參數(shù)化特征造型開發(fā)的Soildworks軟件。
在本次畢業(yè)設(shè)計中，我將使用UG這款軟件進(jìn)行三維造型和加工仿真。因?yàn)閁G相比其他軟件，在復(fù)雜的零件的建模過程中，相對來說比較容易，特別是在曲面建模方面，其曲面構(gòu)造工具比較豐富。在CAM方面的功能也非常強(qiáng)大，它能自動進(jìn)行數(shù)控編程，但是數(shù)控編程之前的加工工藝的分析和規(guī)劃必須由用戶自行完成。加工工藝制定的好壞從根本上決定了數(shù)控程序的優(yōu)劣。加工工藝分析和規(guī)劃的主要內(nèi)容包括：毛坯工件的選擇、加工區(qū)域的確定、工藝路線的擬定、加工刀具的選擇、走刀路線和切削用量的確定等內(nèi)容。這也是我本次畢設(shè)要學(xué)習(xí)的重點(diǎn)。
四、擬解決的關(guān)鍵問題
1．使用三維軟件對汽車典型零部件進(jìn)行建模，應(yīng)注意在曲面部分比較復(fù)雜；
2．加工方案和加工參數(shù)的確定；
3．利用計算機(jī)進(jìn)行輔助編程時應(yīng)注意的關(guān)鍵點(diǎn)及如何最有效實(shí)現(xiàn)加工優(yōu)化及成本優(yōu)
化；
五、研究思路和方法
1.技術(shù)措施和方案
1．利用所學(xué)的知識以及查閱相關(guān)的資料，對典型汽車零部件進(jìn)行幾個加工方案的實(shí)施，
然后進(jìn)行仿真，以對比加工參數(shù)選擇的優(yōu)劣；
2．查詢相關(guān)資料，詢問專業(yè)老師，定義零件的各項(xiàng)參數(shù)以及其加工工藝；
3．運(yùn)用CAM對典型零部件進(jìn)行數(shù)控編程仿真及個別實(shí)物現(xiàn)場加工；
2.解決的技術(shù)途徑
1．查閱相關(guān)技術(shù)資料進(jìn)行研究、分析；
2．利用網(wǎng)絡(luò)及相關(guān)教程進(jìn)行學(xué)習(xí)編程軟件操作技巧，熟練應(yīng)用主流CAM軟件進(jìn)行加
工工藝方案的實(shí)現(xiàn)；
3．向?qū)I(yè)老師請教來解決建模，加工仿真等問題。
六、本課題的進(jìn)度安排
2013.10.08——2013.11.30 收集相關(guān)資料，確定畢業(yè)設(shè)計課題
2013.12.01——2013.12.17 學(xué)生完成課題研究與設(shè)計方案論證報告交給指導(dǎo)教師，完成課題開題報告
2013.12.18——2014.01.31 學(xué)習(xí)UG或Mastercam三維軟件并完成典型零件加工方案確定
2014.02.01——2014.03.10 實(shí)現(xiàn)UG或Mastercam環(huán)境下典型零件的運(yùn)動仿真，并完成相關(guān)典型零件的制作數(shù)控加工加工程序編制，完成中期報告
2014.03.11——2014.04.15 進(jìn)行0號裝配圖紙繪制及論文撰寫等工作
2014.04.16——2014.04.25 完成論文撰寫及各類圖紙繪制、各數(shù)控程序的匯總及必要表格的歸納，并提交給指導(dǎo)老師
2014.04.26——2014.05.09 指導(dǎo)教師評閱畢業(yè)論文，學(xué)生及時積極修改指導(dǎo)老師指出的問題，準(zhǔn)備畢業(yè)設(shè)計答辯內(nèi)容
2014.05.10——2014.05.16 完成答辯
七、參考文獻(xiàn)
[1] 閻紅娟《數(shù)控自動編程參數(shù)設(shè)置技巧》化學(xué)工業(yè)出版社
[2] PeterSmid《數(shù)控編程手冊(原著第3版)》化學(xué)工業(yè)出版社
[3] 尚廣慶《數(shù)控加工工藝及編程》上海交通大學(xué)出版社
[4] PeterSmid《數(shù)控編程技術(shù):高效編程方法和應(yīng)用指南》化學(xué)工業(yè)出版社
[5] 顧雪艷《數(shù)控加工編程操作技巧與禁忌》機(jī)械工業(yè)出版社
指導(dǎo)教師意見
指導(dǎo)教師（簽名）：
年 月 日
所在系（所）意見
負(fù) 責(zé) 人（簽章）：
年 月 日
畢業(yè)設(shè)計（論文）中期檢查表
題 目
三維CAD與CAM技術(shù)在數(shù)控加工中的應(yīng)用—典型汽車零部件的CAM編程（曲面）
姓 名
學(xué) 號
原畢業(yè)設(shè)計（論文）的進(jìn)度計劃：
2013.10.08——2013.11.30 收集相關(guān)資料，確定畢業(yè)設(shè)計課題
2013.12.01——2013.12.17 完成課題研究與設(shè)計方案論證報告交給指導(dǎo)教師，完成課題開題報告
2013.12.18——2014.01.31 學(xué)習(xí)UG或Mastercam三維軟件并完成典型零件加工方案確定
2014.02.01——2014.03.10 實(shí)現(xiàn)UG或Mastercam環(huán)境下典型零件的運(yùn)動仿真，并完成相關(guān)典型零件的制作數(shù)控加工加工程序編制，完成中期報告
2014.03.11——2014.04.15 進(jìn)行0號裝配圖紙繪制及論文撰寫等工作
2014.04.16——2014.04.25 完成論文撰寫及各類圖紙繪制、各數(shù)控程序的匯總及必要表格的歸納，并提交給指導(dǎo)老師
2014.04.26——2014.05.09 指導(dǎo)教師評閱畢業(yè)論文，學(xué)生及時積極修改指導(dǎo)老師指出的問題，準(zhǔn)備畢業(yè)設(shè)計答辯內(nèi)容
2014.05.10——2014.05.16 完成答辯
中期報告（已完成的研究內(nèi)容，所取得階段性成果，下一步工作計劃和研究內(nèi)容等）
1.對典型汽車零部件進(jìn)行測繪，并用UG進(jìn)行三維建模，可以提交三維造型。
2.用UG導(dǎo)出A0圖紙，并用CAD進(jìn)行修改，可以提交A0
3已完成畢設(shè)翻譯
4接下來將進(jìn)行對某汽車零部件的建模和CAM編程（曲面），工藝分析，優(yōu)化分析等等，并完成論文
指導(dǎo)教師意見：
指導(dǎo)教師簽字：
年 月 日
畢業(yè)（論文）指導(dǎo)記錄表
題 目
三維CAD與CAM技術(shù)在數(shù)控加工中的應(yīng)用—典型汽車零部件的CAM編程（曲面）
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指 導(dǎo) 內(nèi) 容
1.A0圖紙的標(biāo)注問題
2.A0圖紙的零件問題
3.畢業(yè)設(shè)計的某些內(nèi)容修改
學(xué)生簽名： 指導(dǎo)老師簽名：
指 導(dǎo) 內(nèi) 容
1.A0圖紙的修改
2.畢業(yè)設(shè)計的格式修改
學(xué)生簽名： 指導(dǎo)老師簽名：
指 導(dǎo) 內(nèi) 容
1.A1圖紙修改
2.畢業(yè)設(shè)計增添一些內(nèi)容
學(xué)生簽名： 指導(dǎo)老師簽名：
指 導(dǎo) 內(nèi) 容
1.A1圖紙修改
2.論文格式最終修改
學(xué)生簽名： 指導(dǎo)老師簽名：
指 導(dǎo) 內(nèi) 容
學(xué)生簽名： 指導(dǎo)老師簽名：
指 導(dǎo) 內(nèi) 容
學(xué)生簽名： 指導(dǎo)老師簽名：
外文原稿和翻譯稿
Corrosion Prevention for Magnesium Automotive Component
LIU Xinkuan XIANG Yanghui HU Wenbin DING Wenjiang
(State Key Lab of Metal Matrix Composite，Shanghai Jiaotong University，Shanghai 200030)
Abstract： With rapid growth of magnesium alloy applications in automotive industry，especially for external components，corrosion prevention is becoming increasingly impotrant．This paper discussed the methodology for corrosion protection of automotive components，particularly for the external components. Further more，the possible technical solutlons of galvanic corrosion for using magnesium components in automotive industry was described．
Key words :magnesium alloys，corrosion prevention，automotive components
Automotive industry has recognized the advantages of magnesium alloy for a long time. In the 1930s of the last century,, there are some earliest applications and then gradually increase the application, the use of magnesium alloy reached its peak in 1971, when Volkswagen Beetle car consumes 42000t magnesium, accounting for almost the entire Western world magnesium production of 1 / 4. Beginning in the 1970s, as prices ,corrosion and other factors, the amount of magnesium in the automotive industry gradually declined. But in the last decade, the amount of magnesium in the automotive industry continues to increase, the annual growth rate of 15%, this growth rate is expected to continue for 10 years. Now, the using of magnesium in the North American automotive industry is about 3.5kg / car. In the future, every car will use at least 100kg of magnesium.
Magnesium alloys in automotive industry are mainly used for the production of two types of components: one is the case. For those high strength is not necessary for all housing components, magnesium alloy is the material of choice. These parts are considerable, clutch shell, valve cover, gear box, crankshaft box, engine front cover, cylinder head and cylinder head cover etc.. Another part is the support. Although magnesium alloy can not be used for making automobile big stress components, but can be used for the production of structural components of a small force, such as the steering wheel, steering rack etc.. Magnesium alloy is particularly suitable for manufacturing often bear the brunt of the components, such as the steering shaft, the seat frame and the hub etc.. From the perspective of corrosion protection of magnesium alloy automobile parts, can be divided into internal and external parts under the hood parts and parts. Different automobile parts subjected to different local environments and different appearance requirements. Protection measures of course are also different. Discuss separately below corrosion and protection of magnesium alloys parts of several types of. The most serious corrosion problems encountered external parts, is the focus of this article
1. Corrosion and Protection of magnesium alloy components
1.1 Internal parts as well as parts under the hood
Support parts such as instrument panel, steering wheel, the steering bracket in the carriage, belonging to the inner parts, the service environment is mainly moisture, no appearance requirements. Therefore, almost do not need to consider the problem of corrosion protection of magnesium alloys. Also do not need to take protective measures.
The shell parts such as gear box, clutch housing generally located in the car under the hood, the service environment is the atmospheric environment, the occasional water splash, general corrosion is not the main problem, magnesium alloy of high purity itself has sufficient corrosion resistance. You need to consider is to prevent galvanic corrosion, the protection measures of galvanic corrosion will be discussed separately below.
There are some cover components such as the valve cover, the oil pan and other higher, with the appearance, durability requirements, to heat, oil, salt water splash, must carry on the surface treatment. Epoxy or epoxy use chitosan powder coating can meet the requirements.
1.2 External parts
1.2.1 The external parts facing new problem
External parts such as doors, the trunk cover and front some pieces of the structure, the working condition is bad, such as industrial atmospheric corrosion, stone, sand, salt spray, ultraviolet irradiation, also called the beautiful appearance. So it must be necessary treated before to meet the requirements . In addition, the magnesium alloy external parts service period relative to other materials will meet many new problems in the manufacturing process of automobile and vehicle .
?The production of automobiles, automobile coating must pass before phosphating / E coating, zinc, aluminum and steel parts for, do not need any treatment can be assembled, and before the assembling of magnesium alloy parts must be processed
?Phosphating treatment standards can not meet the requirements of the binding force of magnesium alloy coating
?The phosphating solution is acidic, will lead to the dissolution of magnesium alloy and magnesium ions, and cause the processing liquid pollution, will reduce the other metal phosphating treatment efficiency
?Iron ions in phosphating solution deposited on magnesium surface, so that the corrosion resistance of magnesium alloys decrease
New problems encountered during the service process of the magnesium alloy parts in the galvanic corrosion. When the magnesium alloy directly in the assembly or heterogeneous metal coating on magnesium alloy surface damage, it is prone to galvanic corrosion. Therefore, to prevent galvanic corrosion will be priority
1.2.2 Batter deal
Magnesium alloy member surface coating treatment may be applied to select the pretreatment or anodizing treatment plus closed , .
Pretreatment general chemical conversion coating . Chromate treatment effect , of course, very good, but chromate serious pollution of the environment , from the environmental point of view, priority should be given a non- chromate treatment, such as phosphate treatment . Common organic paint coating , e.g. ,
E coating or powder coating .
Cost considerations , of course, hope that will solve the problem monolayer , monolayer must be strong enough , however , got enough to withstand damage during assembly . The E a single coating becomes too thin. Too fragile to be coupled with a layer of polymer or resin powder coating thickness exceeding 40pm to avoid damage during assembly .
Anodized to provide a good corrosion preventing effect , the anodized film is generally hard and wear resistant enough to withstand damage during assembly , and the anodic oxide film and the substrate with a strong force , the entire body can be used as a substrate coating , Thus , anodic oxide film on the performance enough to replace pretreatment plus coating layer . The only drawback is anodized high cost , and a porous anodic oxide film . There must be follow- closed treatment , in order to cope with the harsh corrosive environments .
1.3 Handling car tires circle
Car tire service conditions in the external part of the circle to withstand the most severe , requiring tire laps splashing salt water , heat , oil and UV rays. There brake dust, stones hit, also requires a beautiful appearance . Taking into account the ease and the color transformation in acidic environment , preferably coating technology ; considering flying rocks and other factors lead to corrosion damage to the coating applied to the magnesium alloy of the tire beads and the coating layer 5 is usually done baking total film thickness of up to 160 ~ 180μm.
Base treatment before painting is currently the best method is anodized magnesium alloy after chromate bright anodized greatly improved corrosion resistance . Production of automobile tires circle magnesium alloy anodized AM60B applicable law is DOwl, DOw7, DOw22, which Dow22 method works best. The oxide film is much higher in the method of generating the magnesium content than chromium oxide film which is formed on the aluminum alloy of the chromium content , even if the film off , can also achieve the purpose of long-term corrosion resistance .
Primer coating. Due to the poor corrosion resistance of the alloy pan , it is necessary to full coating, to achieve the full effect of a uniform , preferably electrophoretic coating. Electrophoretic coating anionic and cationic there , both compared to cationic better .
Just layer electrophoretic film can not completely prevent splashing paint damage caused by rocks , this also needs to be able to absorb the rocks coated with a coating of energy , this layer is crucial to choose a good first layer electrophoretic coating to adapt the film layer . Good paint and adaptability necessary thickness to be determined by the test .
To prevent paint damage caused by flying rocks and the need to further improve the overall corrosion resistance of the coating thickness of the third film , the requirements of this layer and the second layer and the internal stress from difficult .
The fourth layer of paint color choice is good, good weather resistance coating .
After the above-described magnesium alloy surface treatment, the corrosion resistance , corrosion resistance after splashing rocks . Atmospheric corrosion can reach practical requirements.
1.3 Galvanic corrosion
Magnesium alloy metal relative to other projects in terms of both the anode , magnesium alloy and when assembled together dissimilar metals , galvanic corrosion will need to be carefully considered. Measures to prevent galvanic corrosion , including appropriate structural design , matching metal selection, painting , and washer selection.
Structural Design
Magnesium alloy is applied to the automotive industry, the design principle is to ensure proper water flow out smoothly , but can not let dust and dirt accumulation.
Choose a tight pair of metals and solids
Compatible with the magnesium alloy metal with a low copper content aluminum alloys ( 5000, 6000 series aluminum alloys ) , zinc, tin alloy , the two materials are more commonly used to improve the compatibility of the plating layer and the steel material of magnesium , while the steel, nickel , copper , titanium, and aluminum high copper content , you should try to avoid direct contact with the magnesium.
Select the fastener is relatively critical factor. In sufficient strength . Stuck without considering the case, the compatibility of an aluminum alloy ( 5000, 6000 series aluminum alloy ) as the fastener can be reduced galvanic corrosion. But in most cases, the mechanical performance and price factors determine the use of plating or other ways to protect steel fasteners.
Type in the plating layer , zinc and magnesium is the most compatible. Electric galvanizing process is highly developed, the zinc coating is also very economical , this type of coating has been shown to be effective in reducing the galvanic corrosion between steel and magnesium .
Washer
The role of the gasket is between the current cutting assembly , thereby preventing or reducing the galvanic corrosion. Experimental results show that with the increase of galvanic corrosion gasket thickness decreases linearly . Extrapolated from the experimental curve , with about 4mm thick washers , galvanic corrosion is reduced to negligible . Taking into account the high conductivity of the salt spray test , the data obtained is very conservative . In actual use , the gasket thickness of 2mm or 3mm is enough .
The galvanic corrosion of painting magnesium
In order to prevent galvanic corrosion and coating on magnesium alloy is often the opposite effect. But in some cases, the magnesium alloy parts coating is inevitable, then, coating system selection should be carefully considered. If the magnesium alloy can't get the right protection, the possibility of galvanic corrosion is very large. Therefore, it is necessary to use a thick coating and suitable gasket to prevent the assembly parts insulation layer damage. The galvanic corrosion in the area of effect is very significant. Heterogeneous metal / Mg area ratio increasing, the corrosion rate of the magnesium on the higher. For example, M8 magnesium workpiece with bolts, bolt head area of approximately 3cm 2, when the hole with diameter of LMM coating on magnesium (corresponding to an area of approximately 0.008cm 2), when the area ratio of cathode to anode is 3 / 0.008=375 corresponds, magnesium is not performed on the coating, the area ratio of cathode to anode is 1. If a conductive film, magnesium corrosion will accelerate the speed of 375 times (of course, due to polarization, magnesium corrosion rate does not actually increased 375 times, but the corrosion rate will undoubtedly increase many).
As mentioned above , in order to prevent galvanic corrosion , washers are indispensable. The same is true when the plastic washers may well prevent galvanic corrosion occurs even when there is no protective coating on magnesium. This is mainly due to the increase of the length of the plastic washers conductive channel while reducing the metal ion transfer between the cross-sectional area , of course, galvanic corrosion is reduced . Another benefit of using a plastic protective coating is able to prevent damage during assembly coating system . Of particular note is that the plastic is not high temperature, the temperature of the commonly used phosphate / E- coating system uses 177 ℃, time is about 30min, this treatment can cause brittle plastic cracking. Therefore , do not need plastic washers can be applied only some parts of phosphate / E- coat system.
Aluminum alloy and magnesium alloy washers can also improve the assembly galvanic corrosion in some way . The biggest advantage of aluminum is injury much higher than the strength of aluminum plastic and therefore able to withstand during assembly process .
2 Summary
As for fuel consumption and e
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