3920 轉(zhuǎn)塔式數(shù)控加工中心設(shè)計(jì),塔式,數(shù)控加工中心,設(shè)計(jì) 河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- II -轉(zhuǎn)塔式數(shù)控加工中心設(shè)計(jì)摘 要數(shù)控機(jī)床是一種高科技的機(jī)電一體化產(chǎn)品，是現(xiàn)代制造技術(shù)中不可缺少的生產(chǎn)手段。隨著科技的不斷發(fā)展，數(shù)控機(jī)床在國內(nèi)也進(jìn)入了實(shí)用化階段，但在目前我國許多國營大廠都有一批老機(jī)床，若在老機(jī)床的基礎(chǔ)上對其進(jìn)行改造，配以數(shù)控技術(shù)，這樣不僅可降低成本，而且可提高老機(jī)床的使用壽命。因此，我們畢業(yè)設(shè)計(jì)的題目就是將普通銑床改為集鏜、銑、鉆為一體的八軸轉(zhuǎn)塔式簡易加工中心，實(shí)現(xiàn)不用人工換刀的情況下，短時間內(nèi)進(jìn)行鏜、銑、鉆的轉(zhuǎn)換，這樣不僅可以提高生產(chǎn)效率和加工精度，并且還可以降低成本。我主要負(fù)責(zé)機(jī)床的整體布局和八軸轉(zhuǎn)塔自動換刀裝置的設(shè)計(jì)。在機(jī)床的整體布局方面，我從人機(jī)工程學(xué)和產(chǎn)品造型兩方面對機(jī)床進(jìn)行設(shè)計(jì)。八軸轉(zhuǎn)塔自動裝置的工作原理是在八個軸上事先根據(jù)工序的安排將加工中所需要的刀具裝夾好，當(dāng)將油注入中心油缸后，產(chǎn)生壓力帶動整個轉(zhuǎn)塔頭使八軸轉(zhuǎn)塔旋轉(zhuǎn)，使其實(shí)現(xiàn)自動換刀的功能。這套簡易的數(shù)控加工中心也應(yīng)用了近年來才發(fā)展起來的變頻技術(shù)，從而提高了其中的科技含量。由于現(xiàn)在國內(nèi)的國營大廠都面臨老機(jī)床淘汰的情況，因此在老機(jī)床的基礎(chǔ)上進(jìn)行數(shù)控改造是很有市場前景的，從而進(jìn)行這次畢業(yè)設(shè)計(jì)也是比較實(shí)用的。關(guān)鍵詞：數(shù)控技術(shù)，八軸轉(zhuǎn)塔頭，變頻技術(shù)，自動換刀河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- I -軸 承 套軸 承 材 料軸承的減磨性是與軸和軸承材料及潤滑劑有關(guān)的。軸承材料是根據(jù)與鋼軸頸或不常用的鑄鐵軸頸相配合選擇的。這是因?yàn)?，軸的成本比軸承襯的成本高（尤其就曲柄軸和其他主軸而言） ，其磨損也必須比軸承襯的小。又因?yàn)檩S頸的硬度越大，可靠性越好，所以通常要提高軸頸的硬度。因此，與高速運(yùn)轉(zhuǎn)軸頸相配合的軸承的硬度也會被增加到 55—60RC（滲碳后） 。軸承材料的總體要求符合軸承工作的基本準(zhǔn)則。因此，軸承的材料應(yīng)具備以下幾點(diǎn)要求：（1）應(yīng)具有減磨性。減磨性是通過相配軸頸的摩擦系數(shù)和工作表面溫度來進(jìn)行描述的；（2）有較好的耐磨性；（3）具有較高的疲勞強(qiáng)度。除此之外，軸承的材料還應(yīng)具有以下幾條基本性質(zhì)：（1）傳熱性。對摩擦表面進(jìn)行的熱處理和較低的材料線性膨脹系數(shù)，可避免軸承在工作時產(chǎn)生過大的間隙；（2）跑合性。減少局部應(yīng)力在加工過程中引起的彈性變形和誤差；（3）能保證摩擦潤滑，并能形成穩(wěn)定且可快速恢復(fù)原狀的油膜；（4）耐腐蝕性好；（5）彈性模量低。還有一些重要的性質(zhì)如：可鑄性，切削性等。對于抗磨材料來說，最有用的結(jié)構(gòu)是在材料中加入一些較硬的成分。根據(jù)它們的化學(xué)成分，具有抗磨性的軸承材料可分為下面幾種類型：（1） 金屬材料：如巴氏合金，青銅，鋅基合金，鋁基合金，抗磨鑄鐵等；（2） 粉末冶金材料；（3） 非金屬材料：如塑料，硬木，橡膠等。軸承金屬。巴氏合金被長期運(yùn)用在工程上的軸承合金。它們是以錫或鋁為基體，具有硬度低（常在架或殼體中使用） ，跑合性好的特點(diǎn)，并且對軸頸的硬度和摩擦表面狀態(tài)的要求較低。B83,B89 系列的高錫巴氏合金被應(yīng)用于高速運(yùn)轉(zhuǎn)和高壓的場合。它們可河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- II -以在壓力達(dá)到 p=200kgf/cm2 和 pv=1000kgf-m/cm2-s 的條件下工作。為了避免膠合，只有巴氏合金才能在溫度高達(dá) 110°C 的環(huán)境下工作。其典型應(yīng)用是，由巴氏合金為材料的汽渦輪機(jī)和電力發(fā)電機(jī)及電動機(jī)中的軸承，高錫使軸頸的磨損最小。高錫巴氏合金的缺點(diǎn)是疲勞強(qiáng)度低，這限制了其在沖擊型機(jī)械和高速活塞機(jī)械中的應(yīng)用。而且由于它們的晶體是分層堆積的，故它們不能在需要薄層材料的地方使用。蘇聯(lián)汽車使用的軸承襯是由一層 COC6-6(88% 鉛，6% 錫，和 6%銻)系列的巴氏合金和含有由 40%鎳和 60%銅燒結(jié)而成的含陶合金的鋼襯組成。層與層之間的凝聚力非常好，因?yàn)橄聦颖蛔⑷肓税褪虾辖鸷秃蘸辖?，所以表面凝聚力增?qiáng)了。從另一個方面來說，含陶合金在鋼襯內(nèi)擴(kuò)散，因此，這個系列的巴氏合金的疲勞強(qiáng)度被增加了。并且，由于不含硬物質(zhì)，故軸的磨損較小。另外，其在高生產(chǎn)力的制造業(yè)中也得到了廣泛應(yīng)用。BK2 系列的含鈣巴氏合金，被用于柴油機(jī)引擎制造業(yè)中。被長期應(yīng)用于工程工業(yè)中的是 B16 和 BH 的錫—鉛巴氏合金，其特性與高錫巴氏合金相似(p<=150 kgf/cm2 ,pv<=500kgf-m/cm2-s).BK 系列的巴氏合金，適用于中載荷的場合。它不含錫，并常用于如鐵路所有機(jī)車的軸承的類似場合。BC 系列的巴氏合金是一種不太貴的合金，它常被用于輕載的情況。軸承青銅Bp.C-30 系列的銅鉛軸承合金，常用與高速和高壓(壓力高達(dá) p=300 kgf/cm2)的場合。尤其是在不同負(fù)載的典型內(nèi)燃機(jī)中的應(yīng)用。它比高錫巴氏合金的疲勞強(qiáng)度大。這種銅鉛合金相對于巴氏合金來說，對軸頸的硬度和軸頸、軸承襯的表面光潔度，及對由于油被氧化而導(dǎo)致腐蝕時所要用的潤滑劑都有較高的要求。軸的磨損比用巴氏合金做成的軸承襯的磨損大。若將其中鉛的含量增加35%，則可減少磨損。銅鉛合金是嵌入或鑄在軸承襯中使用的。但是，由于其易產(chǎn)生腐蝕，所以銅鉛合金在近幾年來很少被使用。在重要的軸承和軸承襯的表面應(yīng)被涂上一層薄薄的鉛錫合金或銦或錫的磨合運(yùn)轉(zhuǎn)層。Bp.Ф10-1 型的萬用銅錫合金適用于高壓和中速的場合。但是，由于錫河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- III -的含量過高，故其使用范圍受到限制。一般說來，不應(yīng)將這種軸承青銅應(yīng)用于復(fù)合金屬的軸承襯中。復(fù)合錫鋅青銅（通過重熔獲得） ，如 Bp.OЦC6-6-3 系列被廣泛應(yīng)用于中載荷的情況。鋁鐵青銅在一定壓力，低速，和與硬度被加強(qiáng)了的軸頸相配的條件下，可以作為軸承材料。近幾年來，鋁基軸承合金已經(jīng)越來越多的被人們所使用。因?yàn)樗鼈兊某杀据^低，故較經(jīng)濟(jì)實(shí)惠。這種合金的密度低，耐腐蝕性差，傳熱性好，彈性模量低，疲勞強(qiáng)度高。在將它們運(yùn)用到通過旋轉(zhuǎn)的方法來獲得鋼襯的技術(shù)中后，其用途就越來越多了。無錫的鋁基軸承合金 具有很好的減磨性。但是，在高速運(yùn)轉(zhuǎn)的場合 其減磨性也不是很好。它們對油中的污垢很敏感，且具有較高的線性膨脹系數(shù)。在蘇聯(lián)得到廣泛應(yīng)用的是，用 ACM 系列的無錫鋁基合金來制作的拖拉機(jī)引擎中的軸承。然而，當(dāng)嘗試將它們應(yīng)用于高速運(yùn)轉(zhuǎn)的汽車引擎軸承時，卻沒有成功。最好的軸承材料是具有抗磨性好﹑疲勞強(qiáng)度大的特性的鋁錫抗磨合金。常用的鋁錫抗磨合金為 A09-2 系列（9% 錫，2% 銅，鑄件并且作為非金屬使用） ，A09-2B 系列（鑄件并作為復(fù)合金屬使用） ，A09-1 系列（通過滾軋制成并作為復(fù)合金屬使用）和 A020-1 系列（通過滾軋制成并作為復(fù)合金屬使用） 。這些合金都具有最好的結(jié)構(gòu)。且在沒油的情況下，能在軸頸上形成一層錫保護(hù)膜。例如，A09-1 和 A09-2 系列，被有效地運(yùn)用于柴油機(jī)車，輪船和重型拖拉機(jī)中，內(nèi)燃機(jī)上的軸承。對于鋅軸承合金，人們最為熟悉的應(yīng)該是 ЦAM10-5 系列（10% 鋁，5% 銅，和 85% 鋅） ，由于這種合金具有抗磨性好，組成原料豐富，成本低，及加工過程簡單的特點(diǎn)，因此它在某些場合，常常用來取代 B16 系列的巴氏合金和軸承青銅。這種合金的缺點(diǎn)是跑合性較差，對與其配合的軸承的表面精度要求很高，而且其線性膨脹系數(shù)也很高。由這種材料所做成的軸承，所能承受的最高溫度為80°C。它是鑲鑄或嵌入軸承襯中使用的。一種新的軸承合金是 ЦAM9-1.5 系列；一種由已經(jīng)發(fā)展起來的制造復(fù)合金屬材料的技術(shù)加工而成的合金材料。實(shí)驗(yàn)表明，它具有很好的耐磨性。多層復(fù)合金屬軸承的應(yīng)用現(xiàn)在在不斷的增加。例如在汽車引擎中的軸承，河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- IV -其軸承襯是由含有具有較好傳熱性和較大疲勞強(qiáng)度的 0.25mm 的銅鉛合金﹑極薄的防止錫擴(kuò)散的鎳或銅鋅合金﹑和具有抗磨性及跑合性好的 25μm 厚的錫鉛合金組成的鋼襯?？鼓ヨT鐵（蘇聯(lián) Std GOST 1585-70）可應(yīng)用于低速中等載荷的軸承。軸頸的硬度必須大于鑄鐵襯的硬度。其工作表面必須小心跑進(jìn)油中所用石墨的一種膠質(zhì)混合物。許用壓力隨著轉(zhuǎn)速的增加而急劇下降。鑄鐵襯尤其對局部壓力，沖擊載荷，和所用的不太好的潤滑劑等都是非常敏感的。經(jīng)過實(shí)踐證明，在其中加入氫化物是提高其性能的有效途徑。粉末冶金材料（含陶合金）這種經(jīng)過高壓制模和高溫?zé)Y(jié)而成的金屬粉末，也可不太好的潤滑油中工作。這種材料具有多孔組織，其中孔占體積的 15%—40%。在由該材料做成的軸承中，這些孔都被注滿了油（熱油是通過軸承襯被注入的） 。被廣泛應(yīng)用的鐵—石墨材料中，含有 1%—3%的石墨，剩余的都是鐵。和它一樣實(shí)用的含有 10% 錫的銅—石墨材料中，有 1%—4%的石墨，剩余的均為銅。這兩種材料唯一的不同點(diǎn)是，鐵—石墨比銅—石墨要便宜一些。它們應(yīng)用的范圍主要是由它們的自潤滑性決定的。因?yàn)橐恍┲饕妮S承不能用普通的方法進(jìn)行潤滑。在低壓低速的情況下，這種軸承只利用軸承襯孔中的潤滑油就可以工作很長時間?？渍俭w積的 20%—25%的鐵—石墨軸承的允許運(yùn)轉(zhuǎn)條件和所能承受固定載荷的能力為：v, m/s…… 0.5 1 1.5 2 2.5 3 3.5 4p, kgf/cm2…… 70 65 60 55 45 35 18 8非金屬材料作為軸承襯的非金屬材料有：（1）塑料；（2）疊木；（3）各種不同的硬木；（4）橡膠；（5）石墨材料。由于非金屬材料的傳熱性差，所以大部分非金屬材料的本質(zhì)特征是：用水作為潤滑劑以保證適當(dāng)?shù)睦鋮s。只有在低速高壓時，才能用油或乳液來潤滑。當(dāng)用水作為潤滑劑時，可通過在停機(jī)前向軸承中注入一種膠狀潤滑劑（如油脂等）或在軸上覆蓋一層不銹鋼來避免軸被腐蝕。河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- V -應(yīng)用非金屬材料的前提是：（1） 與軸材料不發(fā)生化學(xué)反應(yīng)；（2） 具有較好的跑合性；（3） 塑性好；（4） 用水或其他在機(jī)器中可能是工作媒介的液體潤滑的可行性。塑料軸承襯的主要應(yīng)用場合：（1） 在不能用液體潤滑和完全或部分自潤滑的軸承中是必須使用的（如汽車懸掛裝置，化學(xué)機(jī)械和紡織機(jī)械中的軸承） ；（2） 通過介質(zhì)潤滑的軸承（如潛水泵和一些食品加工機(jī)械） ；（3） 在重載低速的機(jī)器中，軸承不能達(dá)到流體摩擦的工作條件。這可能是由于頻繁的啟動和停止，低速，或因彈性變形及制造誤差而形成的局部高壓。河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- II -轉(zhuǎn)塔式數(shù)控加工中心設(shè)計(jì)摘 要數(shù)控機(jī)床是一種高科技的機(jī)電一體化產(chǎn)品，是現(xiàn)代制造技術(shù)中不可缺少的生產(chǎn)手段。隨著科技的不斷發(fā)展，數(shù)控機(jī)床在國內(nèi)也進(jìn)入了實(shí)用化階段，但在目前我國許多國營大廠都有一批老機(jī)床，若在老機(jī)床的基礎(chǔ)上對其進(jìn)行改造，配以數(shù)控技術(shù)，這樣不僅可降低成本，而且可提高老機(jī)床的使用壽命。因此，我們畢業(yè)設(shè)計(jì)的題目就是將普通銑床改為集鏜、銑、鉆為一體的八軸轉(zhuǎn)塔式簡易加工中心，實(shí)現(xiàn)不用人工換刀的情況下，短時間內(nèi)進(jìn)行鏜、銑、鉆的轉(zhuǎn)換，這樣不僅可以提高生產(chǎn)效率和加工精度，并且還可以降低成本。我主要負(fù)責(zé)機(jī)床的整體布局和八軸轉(zhuǎn)塔自動換刀裝置的設(shè)計(jì)。在機(jī)床的整體布局方面，我從人機(jī)工程學(xué)和產(chǎn)品造型兩方面對機(jī)床進(jìn)行設(shè)計(jì)。八軸轉(zhuǎn)塔自動裝置的工作原理是在八個軸上事先根據(jù)工序的安排將加工中所需要的刀具裝夾好，當(dāng)將油注入中心油缸后，產(chǎn)生壓力帶動整個轉(zhuǎn)塔頭使八軸轉(zhuǎn)塔旋轉(zhuǎn)，使其實(shí)現(xiàn)自動換刀的功能。這套簡易的數(shù)控加工中心也應(yīng)用了近年來才發(fā)展起來的變頻技術(shù)，從而提高了其中的科技含量。由于現(xiàn)在國內(nèi)的國營大廠都面臨老機(jī)床淘汰的情況，因此在老機(jī)床的基礎(chǔ)上進(jìn)行數(shù)控改造是很有市場前景的，從而進(jìn)行這次畢業(yè)設(shè)計(jì)也是比較實(shí)用的。關(guān)鍵詞：數(shù)控技術(shù)，八軸轉(zhuǎn)塔頭，變頻技術(shù)，自動換刀河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- -IIIDESIGN OF TURRET NUMERICAL CONTROL MACHINING CENTERABSTRACTThe numerical control lathe is the kind of Hi-Tech and electromechanics integrated products, is the indispensable means of production in the modern manufacturing technology. With the constant development of science and technology, the numerical control lathe has entered practical stage of taking too at home. But at present in our country, a lot of state-run factories have a batch of old lathes, if we transform to them on the basis of old lathes and mix them with numerical control technology. We can not only decrease the costs, but also raise the service lives of the old lathes. However, our topics of graduation project is to switch the ordinary milling machines to turret numerical control machining center, which have the functions of boring, milling, and drilling. They can realize to the transfer of boring, milling and drilling in the short time in the condition of being not artificial to transfer knives. It can not only improve production efficiency and machining accuracy, but also decrease costs. I’m responsible for the whole overall arrangements of lathe and the design of eight axles turret numerical control machining center. I apply the knowledge of man-machine engineering and model of the products into the whole overall arrangements of lathe. The operation principles of eight axles turret numerical control machining center is to insert cutters in the axles according to the arrangement of working procedure in advance of machining, and after inject the oil into the jar of center,the pressure make eight axles turret to be transferred entirely, this make it to realize the function of transfer knives automatically. This set of simples numerical control machining center have used the frequency conversion technology which was developed in recent years too, thus this improved the scientific and technological content among them. Because the domestic state-run factories all face the situation that the old lathes 河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- -IVneed eliminates now, so there are market prospects very much to carry on the transformation of numerical control on the basis of old lathe, thus it is practical for us to carry on this graduation project. KEY WORDS: the technology of numerical control, eight axles turret, frequency conversion technology, change the knife automatically河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- I -SLEEVE BEARINGSBEARING MATERIALSThe antifriction properties of rubbing pairs are considered in conjunction with the materials of the shaft and bearing, and the lubricant.Bearing materials are chosen for application in a pair with a steel or, much less frequently, cast iron shaft journal. Owing to the fact that the cost of shafts is, as a rule, higher than that of the bearing liners (especially in the case of crankshafts and other main shafts), their wear must be less than that of the liners. The higher the hardness of the shaft journals, the more reliable their performance. As a rule, journals are hardened. Journals running in high-speed bearings are hardened to a high hardness, 55 to 60 Rc (following carburizing).Integrated requirements, complying with the basic criteria of bearing performance, can be made to bearing materials. Thus, they must:(a) be antifrictional, a property characterized by the coefficient of friction in operation in a pair with the material of the shaft journal, and by the temperature at the working surface; (b) have high wear resistance; and (c) have high fatigue strength.Of importance in meeting these integrated requirements are the following basic properties of bearing materials:(a) thermal conductivity, to provide intensive heat disposal from the friction surfaces, and a low coefficient of linear expansion to avoid large changes in the clearances in the bearings during operation;(b) capacity for being run in readily, which reduces edge and local pressures resulting from elastic deformation and errors in manufacture;(c) good wettability with oil and the capacity for forming stable and rapidly restorable oil films on its surfaces; (d) good corrosion resistance;(e) low modulus of elasticity.Also of basic importance are processing properties, such as castability, machinability, etc.The most favorable structure for an antifriction material is one having a plastic matrix into which hard components are embedded.河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- II -With respect to their chemical composition, antifriction bearing materials can be classified into the following large groups:(a) metallic materials: babbitts, bronzes, zinc-base alloys, aluminium-base alloys and antifriction cast irons;(b) sintered metal powders;(c) nonmetallic materials: plastics, wood laminates, rubbers, etc.Bearing Metals. Babbitts are high-quality bearing alloys that have been used for many years in engineering. They are based on tin or lead and are characterized by their low hardness (they are used for casting into a support or housing), good running-in properties, and relatively lower requirements as to the hardness of the shaft journals and to the state of the rubbing surfaces.High-tin babbitts, grades B83, B89, etc. are to be applied for high running speeds and high pressures. They allow operation at pressures up to p=200 kgf/cm2 and pv= 1000 kgf-m/cm2-s. Toavoid burning-out, babbitts are used for temperatures up to 110°C only. Typical applications are in the bearings of steam turbines, and of powerful electric generators and motors. The use of high-tin babbitts leads to minimum wear of the shaft journals.Shortcomings of high-tin babbitts are their relatively low fatigue strength, which restricts their application in impact-type machinery and high-speed piston machines, and the impossibility of applying them in thin layers because of their large crystals.Soviet automobiles use bearing liners with a layer of babbitt, grade COC6-6 (88% lead, 6% tin and 6% antimony), and a cermet sublayer, sintered of a powder with 40% Ni and 60% Cu, on a steel backing. There is excellent cohesion between the layers because the sublayer is impregnated with the babbitt which forms, with the sintered metal, a substantially increased cohesion surface. On the other side, the sublayer diffuses into the steel backing. This grade of babbitt has an increased fatigue strength and, owing to the absence of hard components, its use leads to less shaft wear. Another advantage is that it lends itself to high-production manufacturing techniques (pressforming from strip stock).A calcium babbitt, grade BR2, is used in diesel engine manufacture. Among those long in use in the engineering industries are the tin-lead babbitts, grades B16 and BH, 河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- III -which have properties close to those of the high-tin babbitts (p<=150 kgf/cm2 and pv <=500kgf-m/cm2-s).Calcium babbitt, grade BK, finds application for medium duty. It contains no tin and is used, for instance, for babbitting the bearings of railway rolling stock. A less expensive babbitt, grade BC, is used for light duty applications.Bronzes. At high speeds and pressures (up to p=300 kgf/cm2) and, in particular, for variable loads typical of internal-combustion engines, a leaded bronze, grade Bp.C-30, is used. It has a higher fatigue strength than the high-tin babbitts. Leaded bronze makes higher requirements than the babbitts do to the hardness of the shaft journals (hardening is compulsory),to the surface finish of the journals and liners, and also to the lubricants since oxidized oils cause corrosion. Shaft wear is higher than that with babbitt liners. If the lead content is increased to 35%,the wear can be reduced. Leaded bronze is applied to strip stock from which the liners are pressformed or it is cast into the liner. Owing to the danger of corrosion, the use of leaded bronze has been curtailed in recent years.The working surface of the liners of critical bearings is coated with a thin running-in layer of an alloy of lead with tin, or of indium or tin.Universal tin bronzes of the Bp. OΦ10-1 type provide for efficient performance at high pressures and medium speeds. However, owing to the high tin content, their application is limited. This bronze is not to be recommended for use in bimetallic bearing liners.Secondary tin-zinc-lead bronzes (i.e. ones obtained by remelting), for instance, grade Bp. OЦC6-6-3, have found extensive application and have proved quite satisfactory for medium duty.Aluminium-iron bronzes are used to some extent for bearings subject to considerable pressures at low speeds and operating with a hardened shaft journal.In recent years, aluminium-base bearing alloys have come into use because they are more economical due to the low cost of the basic material. These alloys have low density, low corrosion resistance, high thermal conductivity, low modulus of elasticity and a high fatigue strength. The use of these alloys increased considerably after a technique was developed for applying them to a steel backing by a rolling process.河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- IV -Tinless aluminium bearing alloys have sufficiently high antifriction properties, but at high speeds their resistance to scoring is not very high; they are sensitive to dirt in the oil and have a high coefficient of linear expansion. The most widely used of these alloys in the USSR is grade ACM which is found in the bearings of tractor engines. No favorable results were obtained, however, when attempts were made to apply them in the bearings of automobile engineswhich run at higher speeds.The most promising bearing materials are the aluminium-tin antifriction alloys which have high antifriction properties and high fatigue strength. In use are alloys grade AO9-2 (9%tin, 2%copper, cast in and used as a monometal), AO9-2B (cast in and used as a bimetal), AO9-1(made by rolling and used as a bimetal). and AO20-1 (made by rolling and used as a bimetal).These alloys have optimal structure and are capable, in cases of oil starvation, of forming a protective film of tin on the journal. Alloys AO9-1 and AO9-2, for example, are being efficiently employed in the bearings of internal-combustion engines of diesel locomotives, ships and heavy-duty tractors.Of the zinc bearing alloys, the best known is grade ЦAM10-5(10% aluminium,5% copper and the remainder zinc),Owing to its satisfactory antifriction properties, abundancy of its constituent materials, low cost and simple manufacture, this alloy is widely used in place of type Б16 babbitts and bronzes. Shortcomings of this alloy are its poor running-in properties, and the consequently higher requirements made to the accuracy of the bearing surfaces, and the high coefficient of linear expansion. The highest permissible temperature of such bearings is 80°C. The alloy is used either for cast-in or for pressfitted liners.A new bearing alloy is grade ЦAM9-1.5;a technique has been developed for making bimetallic strip stock. Tests show that it has high wear resistance.Polymetallic multiple-layer bearings are being employed to an ever-increasing extent. Bearings are used, for example, in automobile engines that consist of a steel backing, a 0.25-mm layer of leaded bronze, serving as a compliant cushion with good thermal conductivity and fatigue strength, an extremely thin layer of nickel or a copper-zinc alloy which prevents diffusion of the tin, and, finally, a surface antifriction layer of a tin-lead alloy, 25 microns thick, which has excellent running-in properties.河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- V -Antifriction cast iron (USSR Std GOST 1585-70) can be applied for low-speed moderately loaded bearings. The hardness of the shaft journals must be higher than that of the cast iron liners. The working surfaces should be carefully run in using a colloidal mixture of graphite in oil. The permissible pressures in these bearings drop sharply with an increase in running speed .Cast iron liners are especially sensitive to edge pressures, impact loads, poor lubricant, etc. Sulphocyaniding has proved to be an effective measure for improving their performance.Sintered Metal Powders (cermets). These materials, made of metal powders by compression moulding at high pressure and subsequent sintering at high temperature, are used in connection with their satisfactory operation with poor lubrication. These materials have a porous structure in which the pores occupy from 15 to 40% of the volume. In the finished bearing these pores are filled with oil (by special impregnation of the liners with hot oil). The most widely employed are the iron-graphite liners consisting of 1 to 3% graphite and the remainder, iron. Also used are bronzegraphite liners with 10% tin,1 to 4% graphite and the remainder, copper, but their properties differ only slightly from the much less expensive iron-graphite liners.Their primary field of application is dictated by their property of self-lubrication: these are mainly bearings that are difficult or impossible to lubricate reliably by ordinary means.At low pressures and speeds, sintered bearings can operate for long periods of time with their only lubrication being from the oil in the pores of the liners. Permissible running conditions for iron-graphite bearings having an average porosity of 20 to 25% and subject to a steady load are:v, m / s....... 0.5 1 1.5 2 2.5 3 3.5 4p, kgf / cm2... 70 65 60 55 45 35 18 8河南科技大學(xué)畢業(yè)設(shè)計(jì)論文- VI -Nonmetallic Materials. Nometallic materials employed for the liners of bearings are: (a) plastics, (b) compressed wood (laminated wood), (c) various hardwoods (lignum vitae, boxwood, oak, etc.), (d) rubber, and (e) graphite materials.An essential feature of most nonmetallic bearing materials, due to their low thermal conductivity ,is that the best lubricant for them is water which ensures proper cooling. Oil or an emulsion is required only at low speeds and high pressures.When water is used as the lubricant, corrosion of the shaft in the bearings can be avoided by introducing a plastic lubricant (for instance, grease) into the bearing before stopping the machine, or by coating the shaft with stainless steel.Reasons for applying nonmetallic bearing materials are: (a) no chemical affinity with the shaft material, (b) good running-in properties, (c)products of wear are soft, and (d) the feasibility of lubricating with water or any other fluid which may be the working medium in the machine.The main fields of application of plastic bearing liners are:(1) bearings for which it is impossible to use a fluid lubricant and for which complete or partial self-lubrication is required(automobile suspensions, and the bearings of certain chemical and textile machines);(2) bearings lubricated by the working medium (submersible pumps and certain food-processing machines);(3) bearings of heavy low-speed machinery in which fluid friction running conditions are not always attainable. This may be due to frequent starts and stops, low speeds, or high local pressures resulting from elastic deformation or manufacturing errors.