【機械類畢業(yè)論文中英文對照文獻翻譯】C型攪拌摩擦焊的現(xiàn)狀與發(fā)展【word英文5234字7頁word中文翻譯3066字7頁】
【機械類畢業(yè)論文中英文對照文獻翻譯】C型攪拌摩擦焊的現(xiàn)狀與發(fā)展【word英文5234字7頁word中文翻譯3066字7頁】,機械類畢業(yè)論文中英文對照文獻翻譯,word英文5234字7頁,word中文翻譯3066字7頁,機械類,畢業(yè)論文,中英文,對照,對比,比照,文獻,翻譯,攪拌,摩擦,磨擦,現(xiàn)狀,發(fā)展,word,英文,中文翻譯
C型攪拌摩擦焊的現(xiàn)狀與發(fā)展
1 前言
1991年,英國焊接研究所（The Welding Institute-TWI）發(fā)明了攪拌摩擦焊（Friction Stir Welding-FSW），這項杰出的焊接技術(shù)發(fā)明正在為世界制造技術(shù)的進步做出貢獻。
在國外,攪拌摩擦焊已經(jīng)在諸多制造領(lǐng)域達到規(guī)模化、工業(yè)化的應(yīng)用水平。如在船舶制造領(lǐng)域，在1996年攪拌摩擦焊就在挪威MARINE公司成功地應(yīng)用在鋁合金快速艦船的甲板、側(cè)板等結(jié)構(gòu)件的流水線制造。在軌道車輛制造領(lǐng)域，日本HITACHI公司首先于1997年將攪拌摩擦焊技術(shù)應(yīng)用于列車車體的快速低成本制造，成功實現(xiàn)了大壁板鋁合金型材的工業(yè)化制造。在世界宇航制造領(lǐng)域，攪拌摩擦焊已經(jīng)成功代替熔焊實現(xiàn)了大型空間運載工具如運載火箭和航天飛機等的大型高強鋁合金燃料貯箱的制造，波音公司的DELTA II型和IV型火箭已經(jīng)全部實現(xiàn)了攪拌摩擦焊制造，并于1999年首次成功發(fā)射升空。2000年世界汽車工業(yè)，如美國TOWER汽車公司等就利用攪拌摩擦焊實現(xiàn)了汽車懸掛支架、輕合金車輪、防撞緩沖器、發(fā)動機安裝支架以及鋁合金車身的焊接。2002年8月，美國月蝕航空公司利用FSW技術(shù)研制出了全攪拌摩擦焊輕型商用飛機，并且首次試飛成功。
2 攪拌摩擦焊的技術(shù)特點
攪拌摩擦焊作為一項新型焊接方法，用很短的時間就完成了從發(fā)明到工業(yè)化應(yīng)用的歷程。目前,在國際上還沒有針對攪拌摩擦焊公布的統(tǒng)一技術(shù)術(shù)語標(biāo)準(zhǔn)，在攪拌摩擦焊專利許可協(xié)會的影響下，業(yè)界已經(jīng)對攪拌摩擦焊方法中所涉及到的通用技術(shù)術(shù)語進行了定義和認(rèn)可。下圖示出了攪拌摩擦焊所用到的主要描述性術(shù)語。
攪拌摩擦焊是一種在機械力和摩擦熱作用下的固相連接方法。如圖1所示，攪拌摩擦焊過程中，一個柱形帶特殊軸肩和針凸的攪拌頭旋轉(zhuǎn)著緩慢插入被焊接工件，攪拌頭和被焊接材料之間的摩擦剪切阻力產(chǎn)生了摩擦熱，使攪拌頭鄰近區(qū)域的材料熱塑化（焊接溫度一般不會達到和超過被焊接材料的熔點），當(dāng)攪拌頭旋轉(zhuǎn)著向前移動時，熱塑化的金屬材料從攪拌頭的前沿向后沿轉(zhuǎn)移，并且在攪拌頭軸肩與工件表層摩擦產(chǎn)熱和鍛壓共同作用下，形成致密固相連接接頭。
攪拌摩擦焊具有適合于自動化和機器人操作的諸多優(yōu)點，對于有色金屬材料（如鋁、銅、鎂、鋅等）的連接,在焊接方法、接頭力學(xué)性能和生產(chǎn)效率上具有其他焊接方法無可比擬的優(yōu)越性，它是一種高效、節(jié)能、環(huán)保型的新型連接技術(shù)。
但是攪拌摩擦焊也有其局限性，例如：焊縫末尾通常有匙孔存在（目前已可以實現(xiàn)無孔焊接）；焊接時的機械力較大，需要焊接設(shè)備具有很好的剛性；與弧焊相比,缺少焊接操作的柔性；不能實現(xiàn)添絲焊接。
攪拌摩擦焊對材料的適應(yīng)性很強，幾乎可以焊接所有類型的鋁合金材料，由于攪拌摩擦焊接過程較低的焊接溫度和較小的熱輸入，一般攪拌摩擦焊接頭具有變形小、接頭性能優(yōu)異等特點;可以焊接目前熔焊“不能焊接”和所謂“難焊”的金屬材料如：Al-Cu(2xxx系列) 、Al-Zn(7xxx系列)和Al-Li(如8090、2090 和2195鋁合金)等鋁合金。
另外，攪拌摩擦焊對于鎂合金、鋅合金、銅合金、鉛合金以及鋁基復(fù)合材料等材料的板狀對接或搭接的連接也是優(yōu)先選擇的焊接方法；目前，攪拌摩擦焊還成功地實現(xiàn)了不銹鋼、鈦合金甚至高溫合金的優(yōu)質(zhì)連接。
攪拌摩擦焊可以較容易實現(xiàn)異種材料的連接，例如鋁合金和不銹鋼的攪拌摩擦焊接，利用攪拌摩擦焊可以較方便的實現(xiàn)鋁－鋼板材之間的連接和銅鋁復(fù)合焊接接頭。
3 攪拌摩擦焊在國外的發(fā)展
攪拌摩擦焊作為一種輕合金材料連接的優(yōu)選焊接技術(shù)，已經(jīng)從技術(shù)研究，邁向高層次的工程化和工業(yè)化應(yīng)用階段,形成了一個新的產(chǎn)業(yè): 攪拌摩擦焊設(shè)備的制造、攪拌摩擦焊產(chǎn)品的加工.如在美國的宇航制造工業(yè)、北歐的船舶制造工業(yè)、日本的高速列車制造等制造領(lǐng)域，攪拌摩擦焊得到了廣泛的應(yīng)用,均已形成新興產(chǎn)業(yè)。
4激光輔助攪拌摩擦焊
激光輔助攪拌摩擦焊（LAFSW）是一種新改進的攪拌摩擦焊，攪拌摩擦焊是近10年開發(fā)的工藝。
在攪拌摩擦焊里，焊接熱能是來自工具和工件之間摩擦熱量。由于這種工藝需要相對大的力，因此，在攪拌摩擦焊中使用的設(shè)備笨重且昂貴。激光輔助攪拌摩擦焊用激光能源加熱工件，而攪拌頭的主要作用是攪拌和連接工件2部分。由于這種原因，激光輔助攪拌摩擦焊是一種相對簡單和廉價的方法。
為了克服攪拌摩擦焊中存在的不足，如（1）裝夾焊接工件的夾具較大，需要很大的力向前移動焊接工具，焊接工具磨損率相對高；（2）用感應(yīng)線圈方法加熱不能保證正確的位置、焊接攪拌頭和夾具裝置都受到加熱感應(yīng)線圈的影響及用感應(yīng)線圈作媒介加熱及僅適用于導(dǎo)體材料，并不能用于其他非金屬和非導(dǎo)體材料。人們開發(fā)了的激光輔助攪拌摩擦焊 。這種方法由通用銑床和Nd：YAG激光器改造成的。激光能源在旋轉(zhuǎn)攪拌頭前面有限范圍內(nèi)預(yù)熱工件。這樣，旋轉(zhuǎn)的攪拌頭前面的工件體積、塑性增加（插圖1）。然后，采用與普通FSW工藝一樣的方法連接工件。旋轉(zhuǎn)工具前面的高溫軟化了工件，并且可以不用強大夾具裝夾就能夠保證連接。向前移動焊接工具只需很小的力，所以減少了磨損。對于激光能源這種工藝的優(yōu)點還有焊接能力較高，焊接中不會引起過多的磨損。商業(yè)用的激光器，具有很精確地激光直徑控制裝置，因此，控制工件的受熱區(qū)域和激光源到達工件的數(shù)量，并且保持系統(tǒng)的其他部位的受熱是比較容易的。
目前激光輔助攪拌摩擦焊的焊接工藝已經(jīng)被證明。激光能預(yù)熱工件的使用標(biāo)志著在焊接工具和工件中需要提供較大的力的降低，用這種改進的方法簡化了使用，因此使用經(jīng)濟的焊接方法已成為可能。另外，較高的焊接速度在改進中獲得了較好的效益。
5攪拌摩擦焊――鑄鋁的高效連接技術(shù)
針對ZL114A合金廣泛應(yīng)用，中國攪拌摩擦焊中心對該材料的攪拌摩擦焊工藝適應(yīng)性進行了開發(fā)， 試驗數(shù)據(jù)表明，該材料的攪拌摩擦焊工藝適應(yīng)性良好，接頭抗拉強度達到了母材的91%，接頭力學(xué)綜合性能優(yōu)于電子束等熔焊方法。 ZL114A合金（舊牌號為ZAlSi7Mg1A），是在ZL101A合金基礎(chǔ)上增加Mg元素的含量發(fā)展起來的Al-Si-Mg系高強度鑄造鋁合金。它既具有優(yōu)良的鑄造工藝性能，又具有較ZL101A合金更高的力學(xué)性能。由于其優(yōu)越特性，在航空航天制造業(yè)中，廣泛用于制造重要部位的大型薄壁結(jié)構(gòu)件。ZL114A合金應(yīng)用前景廣闊，產(chǎn)生了對材料高效連接技術(shù)的迫切需求。因采用熔焊方法，熱輸入量較大，焊接變形大，難以滿足薄壁件精度要求；并且焊縫易出現(xiàn)氣孔、夾渣、未焊透、燒穿、裂紋等缺陷，缺陷率高；而且焊前焊后處理工序較繁瑣。 攪拌摩擦焊是一種新興的金屬固相連接技術(shù)，金屬在焊接過程中不熔化，熱輸入量小；焊縫的連接是在金屬受擠壓的狀態(tài)下完成的，焊接接頭不會產(chǎn)生熔化焊焊接接頭的氣孔和裂紋等一類缺陷，焊縫缺陷少；攪拌摩擦焊類似于機械加工過程，容易實現(xiàn)自動化控制，而且沒有熔化焊中的電壓，電流，強光，金屬粉塵等現(xiàn)象，工作環(huán)境環(huán)保清潔。最重要的是，攪拌摩擦焊接頭的力學(xué)性能優(yōu)于熔焊接頭。試驗數(shù)據(jù)表明焊接接頭的抗拉強度達到了母材的91％，試樣延伸率達到了2.5％，接頭組織晶粒細(xì)化、均勻而致密，消除了母材的鑄造缺陷。ZL114A母材與焊接接頭微觀組織對比，可觀察到焊核區(qū)微觀組織是無方向性的、細(xì)小的等軸晶粒，母材區(qū)為粗大的樹枝狀鑄造組織。攪拌摩擦焊是一種區(qū)別于熔化焊和機械連接的新型焊接技術(shù)，基于其技術(shù)優(yōu)勢，在航空制造業(yè)中的應(yīng)用具有巨大的潛在性，為各種輕質(zhì)合金高效連接，提供了解決途徑和方法。
6攪拌摩擦焊接在運載火箭上的應(yīng)用?
運載火箭貯箱常用的材料是比強度高、比剛度高的鋁合金，如2014，2219和7075 鋁合金?，F(xiàn)在，運載火箭貯箱又采用性能更好的2195鋁鋰合金。在航天產(chǎn)品中，特別是在制 造運載火箭貯箱中，焊接工藝是一項關(guān)鍵的制造技術(shù)。熔焊技術(shù)如氣體鎢極電弧焊（GTAW ）和氣體金屬電弧焊（GMAW）自20世紀(jì)50年代起，在雷神、宇宙神、大力神、土星和德爾它 系列運載火箭貯箱的制造中使用了幾十年，從焊接設(shè)備、焊接材料、焊接工藝等方面作了大量的研究工 作，滿足了焊接質(zhì)量的需要。同時，為了提高焊接質(zhì)量和降低成本，20世紀(jì)80年代美國又采 用了變極性等離子弧焊（VPPA）焊機，并配備了先進的計算機控制系統(tǒng)，代替了GTAW和GMAW ，焊接了2219-T87鋁合金制的航天飛機外貯箱，使焊接工藝在貯箱的制造中向前邁進了一 大步。迄今為止，雖然焊接質(zhì)量有所提高，焊接時間有所縮短，但仍不能徹底解決焊縫及近縫區(qū)的裂紋和減少焊接氣孔等缺陷問題。1991年英國劍橋大學(xué)焊接研究所（TWI）發(fā)明了攪 拌摩擦焊接(FSW)。這種焊接技術(shù)焊接的鋁合金變形小、冶金和力學(xué)性能高、成本低和焊接時間短。
挪威在世界上最早用FSW焊接技術(shù)焊接過6 mm×16 m2的6068-T6鋁合金船面板和20 m長的鋁合金制的快艇，焊接總長達10 000 m。瑞士也研制出FSW焊機。為了加速FSW焊 接技術(shù)在工業(yè)上的應(yīng)用，1995年國際合作公司贊助了一項計劃，由TWI研究所牽頭繼續(xù)研究FSW，并用FSW焊接2000系（AlCu）、5000系（AlMg）、6000系（AlMgSi）等鋁合金，并均獲得滿意的焊接質(zhì)量。TWI研究所、美國愛迪生焊接研究所（EWI）等部門，除了研究用FSW焊接鋁合金外，還研究用它焊接黑色金屬及其它金屬。美國的航空航天工業(yè)部門對F SW開展了更多的應(yīng)用性研究，如洛馬公司、波音公司投入了大量的研制經(jīng)費，僅花在FSW 焊接工藝和設(shè)備研制上的費用就達1500萬美元，成功地焊接了德爾它Ⅱ～Ⅳ的運載火箭貯箱 。
由于FSW是在比被焊合金材料熔點溫度低的條件下完成的固態(tài)連接，所以金屬材料沒有熔化，焊接收縮變形小和力學(xué)性能損失低，與傳統(tǒng)的GMAW和GTAW熔焊技術(shù)焊接鋁合金相比，有著突出的優(yōu)點：
a）不需要氬、氦保護氣體和填充材料，焊接時不需要控制焊接電流和電弧電壓參數(shù)，節(jié)省了大量材料的消耗。
b）焊前不需要對被焊接材料和焊絲仔細(xì)清理、酸洗、打磨和烘干等，不必對被焊接材料機械加工開剖口，節(jié)省了許多操作時間。
c）焊工不要求有高的操作技術(shù)。
d）焊接能量效率高，單層焊接6000系鋁合金可達12.7 mm厚度，因此適合于自動 化生產(chǎn)。
e）不存在鋁合金焊接主要缺陷，即裂紋敏感性問題，因此，容易焊接難以焊接的鋁合金材料，如7075鋁合金。
f）由于FSW可以保持合金的冶金性能，所以可焊接金屬基復(fù)合材料和快速凝固材料。
g）采用最佳的焊接參數(shù)，可以獲得無氣孔的焊縫。
h）可以焊接異種金屬，如鑄造和擠壓、鑄造和鍛造材料等。
i）用FSW可以焊接許多通常不能夠焊接的長而大的橫截面零件。
J）焊接大尺寸擠壓件變形很小。
k）焊接前工件裝配要求低，待焊接表面根部不必緊配合，根部裝配間隙允許公差低， 1.6 mm厚薄板根部裝配間隙為0.2 mm，12.7 mm厚板為1.25mm。
?FSW是一項適合于焊接鋁合金的新技術(shù)。因為它是固態(tài)焊接，與熔焊鋁合金技術(shù)相比，具有3個主要優(yōu)點：
a）固態(tài)連接消除了與熔焊有關(guān)的裂紋，即液化或固化裂紋。在最佳焊接條件下完全消除氣孔。
b）不存在焊縫金屬蒸發(fā)產(chǎn)生的合金元素?fù)p失，焊縫合金元素得到保存，因此焊接質(zhì)量得到保證。
c）由于焊接工具對材料產(chǎn)生的碾壓、攪拌和鍛造作用，可得到比基體金屬更為細(xì)小的再結(jié)晶組織，焊縫金屬強度超過了焊接熱影響區(qū)材料的強度。
用于運載火箭貯箱的材料2014-T6高強度鋁合金（中國牌號為LD10）是比較難焊接的金屬材料，其焊接熱裂紋傾向性高，焊接接頭強度系數(shù)為0.5左右，塑性不高，延伸率僅2%～3 %，補焊性能差。FSW焊接后的接頭彎曲試樣證明：接頭塑性明顯提高，彎曲角達180°，拉 伸試樣均斷在焊縫金屬外的熱影響區(qū)。2014-O狀態(tài)拉伸試樣破壞均斷在基體金屬。與熔焊接頭相比，F(xiàn)SW焊接接頭 的抗拉強度高30%～50%，焊接接頭的強度系數(shù)達0.7，斷裂韌性提高，疲勞性能與鉚接 的相同。2519-T87高強度鋁合金有優(yōu)異的沖擊性能，用于海軍先進的水陸兩用攻擊型戰(zhàn)車，但用普通熔焊時，焊接接頭塑性低，不能通過必須的沖擊驗收試驗，經(jīng)FSW焊接后的焊接接頭比熔焊接頭塑性提高，強度相同，成功地通過了彈道沖擊試驗。2195-T8鋁鋰合 金采用FSW焊接，焊接接頭力學(xué)性能比VPPA焊接接頭力學(xué)性能高得多。
FSW發(fā)展很快，已有10年。自從1995年以來，歐洲、美國和日本等一些國家對FSW開展了應(yīng)用性研究，特別是美國航空航天工業(yè)部門高度重視該技術(shù)，并用它 成功地焊接了以往難以焊接的7075鋁合金低溫燃料貯箱，其力學(xué)性能很好。5454鋁合金焊接后有很好的抗腐蝕性。?
當(dāng)前各國都在研究不同鋁合金，不同接頭形狀的焊接，著手建立材料焊接力學(xué)性能數(shù)據(jù)庫，建立飛機和航天工業(yè)用鋁合金焊接標(biāo)準(zhǔn)，并將FSW應(yīng)用擴大到汽車、造船 、鐵路 、建筑、壓力容器等部門。同時研究熔點高的鈦合金材料，包括金屬基材料在內(nèi)的泡沫鋁合金材料的焊接。?
FSW焊接主要依靠設(shè)備完成，研究的重點是夾持器和特型指棒。研究證明：工具的形狀決定了焊縫金屬塑性加熱、熱塑性材料的流動和鍛造形式；夾持器的尺寸決定了焊縫 的尺寸、焊接速度；工具材料決定了摩擦加熱速度、夾持器的強度、工件溫度；所以，夾持器決定了焊縫的最終質(zhì)量。在各國的專利中，為了焊接出最好的力學(xué)性能和冶金性能、完全 無氣孔、光滑表面的焊縫，對各種各樣的特型指棒的形狀分別作了研究；對圓柱形夾持器的直徑2rs、幾何形狀、焊接速度ω、向下的作用力F以及 焊接材料厚度W的最佳配合作了研究，得出了以下結(jié)論：
FSW是一種最新的非常適合于焊接鋁合金的工藝技術(shù)，具有焊接變形小、質(zhì)量高和成本低等優(yōu)點。雖然發(fā)展時間不長，在運載火箭貯箱制造等領(lǐng)域已經(jīng)獲得應(yīng)用，并在進一步 擴大。由于這種焊接工藝在航空航天工業(yè)部門的重要性，又極具潛力，目前關(guān)鍵性的焊接規(guī)范參數(shù)和工具技術(shù)還處于保密階段。我國應(yīng)要盡早開展 FSW在航天工業(yè)上的研究，用于高強度鋁合金制造的產(chǎn)品中。?
FSW-C Current Status and Development
1 Preface
In 1991, the British Welding Research Institute (The Welding Institute-TWI) invented the FSW (Friction Stir Welding-FSW), the invention is excellent welding technology advances in manufacturing technology for the world to contribute.
At Abroad, friction stir welding has been achieved in many large-scale manufacturing, the application level of industrialization. Areas such as shipbuilding, in 1996, friction stir welding in Norway MARINE successfully applied to fast ship aluminum deck, side panels and other structural parts of the assembly line manufacturing. In the rail equipment manufacturing field, the first Japanese company in 1997 HITACHI friction stir welding technology in the train body fast low-cost manufacturing, successful implementation of a large panel of industrial aluminum profiles manufacturing. Aerospace manufacturing in the world, instead of friction stir welding has been successfully implemented large-scale fusion, such as launch vehicles and space launch vehicles and other large-scale space shuttle fuel tank manufacturing high strength aluminum, Boeing DELTA II rocket type and IV have all been Friction stir welding manufacturing implements, and in 1999 the first successful launch. 2000 world automotive industry, automobile companies, such as the U.S. TOWER on the use of friction stir welding to achieve the car hanging bracket, light alloy wheels, anti-collision buffer, engine mounting bracket and the aluminum body of the weld. August 2002, the United States Air eclipse technology developed by the entire FSW FSW light commercial aircraft, and the first successful test flight.
2 The technical characteristics of friction stir welding
The technical characteristics of friction stir welding friction stir welding as a new welding method, using a very short time to complete the invention to the industrial application from the course. At present, no international publication for the unity of friction stir welding technology terminology standards, patent licensing in the friction stir welding under the influence of the Association, the industry has been friction stir welding method of the involved technical terms are defined and recognized. The following figure shows the use of friction stir welding of the main descriptive terms.
FSW is a frictional heat in the mechanical and solid under the action of the connection method. Shown in Figure 1, friction stir welding process, a cylindrical shaft with a special convex shoulders and pin head spinning slowly stirred into the workpiece to be welded, welding materials mixing head and is the shear resistance of the friction between the friction heat generated , So that mixing the first neighborhood of thermal plastics (welding temperature normally does not reach and exceed the melting point of welding materials), when the mixing head spinning move forward, the hot plasticized metal back from the forefront of the pin Along the transfer, and in the mixing head shoulder and the workpiece surface friction and heat and forging together, form a dense solid connectors
FSW with automation and robotics operations for the many advantages, for non-ferrous materials (such as aluminum, copper, magnesium, zinc, etc.) connection, welding, mechanical properties of joints and productivity that has no other welding methods Compare the advantages, it is an efficient, energy saving, environment-friendly new connection technology.
However, friction stir welding also has its limitations, such as: weld at the end there is usually a key hole (hole-free now for welding); large mechanical force during soldering, welding equipment need to have good rigidity; and arc phase Ratio, the lack of flexible welding operations; can not be achieved filler metal welding.
FSW adaptability of materials, almost all types of aluminum alloy welding, friction stir welding process because the lower temperature and smaller welding heat input, the general deformation of friction stir welding head with a small, joint performance And so on; to fusion welding current "can not be welded, " and so-called "hard to weld" the metal materials such as: Al-Cu (2xxx series), Al-Zn (7xxx series) and Al-Li (such as 8090,2090 and 2195 aluminum Alloy) and other aluminum alloy.
In addition, friction stir welding for magnesium alloy, zinc alloy, copper alloy, lead alloys, and aluminum matrix composites and other materials, the connection plate butt or lap welding method is preferred; present, friction stir welding has also successfully achieved Stainless steel, titanium or high-temperature alloys high-quality connections.
Fsw of dissimilar materials can be more easily achieved the connection, such as aluminum and stainless steel by friction stir welding, the use of friction stir welding of aluminum can be more easily achieved - the connection between steel plates and copper and aluminum composite joints.
3 FSW development abroad
FSW in the development of friction stir welding abroad as a preferred light alloy welded connection technology, has moved from technical studies, into a high level of engineering and industrial application stage, the formation of a new industry: friction stir welding equipment Manufacturing, processing and friction stir welding products. If the aerospace manufacturing industry in the United States, the Nordic shipbuilding industries, manufacturing, and other high-speed train in Japan manufacturing, friction stir welding has been widely used, have been the formation of new industries.
4 Laser assisted friction stir welding
Laser assisted friction stir welding (LAFSW) is a new and improved friction stir welding, friction stir welding is a technique developed nearly 10 years.
In friction stir welding, the welding heat from the heat of friction between tool and workpiece. Since this process requires a relatively large force, therefore, the use of friction stir welding equipment cumbersome and expensive. Laser assisted friction stir welding using laser energy heating the workpiece, and the pin connecting the main role is to stir and the workpiece 2. For this reason, laser assisted friction stir welding is a relatively simple and inexpensive methods.
In order to overcome the friction stir welding deficiencies, such as (1) welding the workpiece clamping fixture larger force to move forward requires a lot of welding tools, welding tool wear rate is relatively high; (2) the method of induction heating coil is not To ensure the correct position, welding mixing head and fixtures are subject to the impact of the induction coil and heated by induction coil for heating and only for the media conductor material, and can not be used for other non-metallic and non-conductive material. It has developed a laser assisted friction stir welding. This approach by the general milling and Nd: YAG laser converted into a. Laser energy in the rotating mixing head warm in front of the workpiece within a limited range. In this way, rotating the workpiece in front of the volume mixing head, the plastic increase (Figure 1). Then, the FSW process and ordinary connection the same way as the workpiece. Softening the front rotary tool workpiece, and clamping fixture may not be able to guarantee a strong connection. Welding tools to move forward only a small force, so a reduction of wear and tear. The advantages of this technology of laser energy also welding with higher welding does not cause excessive wear and tear. Commercial use of the laser, the laser has a very precise diameter control device, therefore, control of the workpiece and the laser heat source to reach the regional number of jobs and keep other parts of the heating system is relatively easy.
Currently laser assisted friction stir welding of the welding process has been proven. Preheat the workpiece to the use of laser marks in the welding tool and the workpiece in the need to provide a larger reduction in force, with this improved method simplifies the use of, the use of economical welding method is possible. In addition, the higher the welding speed to obtain a better in improving the efficiency.
5 FSW - Aluminum high-connectivity
ZL114A alloy widely used for the Chinese Center for friction stir welding of the friction stir welding process of adaptation to the development, test data show that the friction stir welding process well adapted, the joint tensile strength of the base metal 91 %, overall performance is better than the mechanical joints such as electron beam welding methods. ZL114A alloy (the old grade is ZAlSi7Mg1A), is based on the increase in ZL101A Mg alloy element content developed Al-Si-Mg system high strength cast aluminum alloy. It has excellent casting properties, but also has higher than the mechanical properties of ZL101A alloy. Because of its superior characteristics, in the aerospace manufacturing industry, the important parts are widely used in the manufacture of large thin-walled structure. ZL114A alloy and promising, resulting in high connectivity for the urgent material needs. By using fusion method, a large amount of heat input, welding deformation, difficult to meet the requirements of thin-walled precision parts; and prone to weld porosity, slag, lack of penetration, burn, cracks and other defects, defect rate; and treatment before welding after welding process more cumbersome. Friction stir welding is a new solid metal connection technique, the metal is not melted during the welding process, a small amount of heat input; weld metal connection is accomplished by squeezing the state, the welded joint does not produce fusion welding pores and cracks, welded joints, and other similar defects, fewer weld defects; similar mechanical friction stir welding process, easy automation, and does not melt welding voltage, current, light, metal dust and other phenomena, the work environment environmental cleaning. The most important is that friction stir welding is superior to the mechanical properties of welded joints. Experimental data show that the tensile strength of welded joints for 91% of the base material, the specimen extension rate of 2.5%, joints grain refinement, uniform and compact, eliminating the base metal casting defects. ZL114A base metal and welded joint microstructure compared to the weld nugget zone can be observed microstructure is no direction, and small equiaxed grains, base metal as a coarse dendritic cast structure. Friction stir welding is a welding and mechanical connections different from the melting of new welding technology, based on its technical advantages in the aviation industry in the application of great potential, for a variety of light alloys and efficient connectivity, and provide a solution methods.
6 FSW applications in launch vehicles
Launch vehicle tanks commonly used material is high specific strength and stiffness than aluminum, such as 2014,2219 and 7075 aluminum alloy. Now, the launch vehicle performance and better use of the tank and aluminum-lithium alloy 2195. Aerospace products, especially in the manufacturing launch vehicle tank, the welding process is a key manufacturing technology. Welding techniques such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) 50 years since the 20th century onwards, Thor, Atlas, Titan, Saturn and the Delta series of launch vehicles used in the manufacture of tanks Decades, from welding equipment, welding materials, welding technology has done a lot of research work to meet the needs of the welding quality. Meanwhile, in order to improve the welding quality and reduce costs, the 20th century, the United States has adopted 80 of variable polarity plasma arc welding (VPPA) welder, and equipped with advanced computer control system to replace the GTAW and GMAW, welded 2219-T87 Space shuttle external tank, aluminum alloy, so that the welding process in the manufacture of the tank a big step forward. So far, though improved weld quality, weld time has been shortened, but still not completely solve the weld and the crack near the weld area and reduce the porosity and other weld defects. University of Cambridge in 1991, Welding Institute (TWI) the invention of friction stir welding (FSW). The welding deformation of aluminum alloy welding, metallurgical and mechanical properties, low cost and welding time is short.
Norway first in the world with FSW welding technique had 6 mm × 16 m2 of 6068-T6 aluminum panels and 20 m long ship's boats, aluminum alloy, welding total length of 10 000 m. Switzerland has developed a FSW welding machine. FSW welding technology in order to accelerate the industrial application, in 1995 co-sponsored an international program led by the TWI Institute continue to study the FSW, and with the Department of FSW welded 2000 (Al Cu), 5000 series (Al Mg), 6000 (Al Mg Si) and other aluminum alloy, and welding quality are satisfactory. TWI Institute, United States Edison Welding Institute (EWI) and other departments, in addition to welded aluminum alloy FSW for research, but also use it to study welding ferrous metals and other metals. U.S. aerospace industry sector F SW carried out more applied research, such as the Luo Martin, Boeing invested a lot of development costs, only spent FSW welding process and equipment development and the costs amounted to $ 15,000,000 The successful welding of the Delta launch vehicles Ⅱ ~ Ⅳ tank.
Since FSW is welded alloy melting point than the low temperature solid-state under the conditions of complete connection, so there is no melting of metallic materials, welding and mechanical properties of small shrinkage loss is low, and the fusion of traditional GMAW and GTAW welding aluminum technology compared to Has outstanding advantages:
a) do not need to argon, helium, shielding gas and filler material, welding need to control the welding current and arc voltage parameters, saving a lot of material consumption.
b) do not need to be before welding wire welding material and careful cleaning, pickling, polishing and drying, do not have to be welded material machining profile mouth open and save a lot of operating time.
c) does not require a high welding technique.
d) welding energy efficient, single-layer welding 6000 series aluminum alloys up to 12.7 mm thickness, and therefore suitable for automated production.
e) there is no major defects in aluminum alloy welding, the crack sensitivity of the issue, therefore, easy to difficult welding of aluminum alloy welding materials, such as 7075 aluminum alloy.
f) Since FSW metallurgical properties of the alloy can be maintained, so I can weld metal matrix composites and rapidly solidified materials.
g) to adopt the best welding parameters, pore-free weld can be obtained.
h) can weld dissimilar metals, such as casting and extrusion, casting and forging materials.
i) can be welded by FSW welding many often can not be a long and large cross-section parts.
J) Large size extrusion welding deformation is small.
k) the workpiece before welding, assembly requirements low, the surface of the roots do not have to be welded tight fit, the root of the assembly gap tolerances low, 1.6 mm thickness of the plate assembly space for the roots of 0.2 mm, 12.7 mm thick as 1.25mm.
FSW is a welding aluminum is suitable for new technologies. Because it is a solid-state welding technology and welding aluminum, compared with three main advantages:
a) elimination of solid-state connection with welding the cracks, that is, liquefied or solidified cracks. Optimum welding conditions in the complete elimination of porosity.
b) there is no weld metal evaporation loss of alloying elements, the weld alloy elements are preserved, so the welding quality is guaranteed.
c) the welding tool on material produced by crushing, stirring and forging the role of the base metal can be obtained more than fine recrystallized weld metal strength over the HAZ material strength.
The material used for launch vehicle tank with high-strength aluminum alloy 2014-T6 (China grades for the LD10) is more difficult to weld metal material, the welding hot cracking tendency of high, welded joint strength factor of about 0.5, the plastic is not high, extending rate of 2% to 3%, welding performance is poor. FSW joints welded bend specimens after the proof: the plastic joints significantly improved, bending angle of 180 °, tensile specimens were broken in the weld metal beyond the heat affected zone. 2014-O state of tensile specimens were broken in the destruction of the base metal. Compared with the welded joints, FSW tensile strength of welded joints and 30% to 50%, welded joint strength factor of 0.7, fracture toughness, fatigue performance and riveting of the same. High-strength aluminum alloy 2519-T87 has excellent impact properties, for the Navy's amphibious attack tanks advanced, but with ordinary welding, the welded joints of low plasticity, the impact can not be acceptance test, after welding by the FSW than the welded joints of welded joints to improve plasticity, strength the same, successfully passed ballistic impact test. 2195-T8 Al-Li alloy by FSW welding, mechanical properties of welded joints than VPPA mechanical properties of welded joints is much higher.
FSW has developed rapidly, over 10 years. Since 1995, Europe, the United States and Japan and other countries to carry out the application of FSW research, especially in the U.S. aerospace industry attach great importance to the technology and used it successfully in the past is difficult to weld 7075 aluminum alloy welding of cryogenic fuel tank its good mechanical properties. 5454 aluminum alloy after welding has good corrosion resistance.
Different countries are studying the current alloy, the shape of the different joints welded, to establish the mechanical properties of welded materials database, the establishment of aircraft and aerospace industry with aluminum welding standards, and broadened the application of FSW to cars, shipbuilding, railways, construction, pressure vessel and other departments. At the same time of high melting point of titanium materials, including metal-based materials, including the welding of aluminum alloy foam.
FSW welding equipment mainly depends on completion of the study focused holder and the special type that sticks. Studies have shown that: Tools determine the shape of the weld metal plastic heating, the flow of thermoplastic material and forging forms; holder size determines the size of the weld, welding speed; tools and materials determines the friction heating rate, grip strength the workpiece temperature; so gripper determine the final weld quality. Patents in various countries, in order to weld the best mechanical properties and metallurgical properties, completely non-porous, smooth surface of the weld on a variety of special type refers to the shape of rods were made of; of the cylindrical clamping the diameter 2rs, geometry, welding speed ω, the downward force F, and welding materials with the thickness W of the best studied, and reached the following conclusions:
FSW is a very suitable for the latest technology in welding aluminum, a welding deformation of small, high quality and low cost. Although the development time is not long, tank manufacturing and other fields in the launch vehicle applications have been received, and further expanded. Because of this welding process in the importance of the aerospace industry sector, but also great potential, the current critical welding parameters and tool technology is still in the secret stage. China should be undertaken as soon as possible FSW research in the aerospace industry for high strength aluminum alloy product.
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