鍛造畢業(yè)論文外文翻譯

1、<p><b>　　附錄A 英文原文</b></p><p>　　A.1 FORGING</p><p>　　Bulk defirnnation of metals refers to various processes, such as forging, rolling, or extruding, where there is a controlled

2、 plastic flow or working of metals into useful shapes. The most well known of these processes is forging where deformation is accomplished by means of pressure, impact blows, or a combination of both. Hammer Forging<

3、/p><p>　　Hanuner forging consists of striking the hot metal with a large semiautomatic hammer. If no dies are involved, the forging will be dependent mainly on the skill of the operator. If closed or impression

4、 dies are used, one blow is struck for each of several (lie cavities. A- gain, productivity and quality depend to a large degree on the skill of the hanimer operator and the tooling.</p><p>　　Press Forging

5、 Press forging is characterized by a slow squeezing action. Again, open or closed dies may be used. The open dies are used chiefly for large, simple-geometry parts that are later machined to shape. Closed-die forging

6、relies less on operator skill awl more on the design of the preform and forging dies.2 As an example of the versatility of the process, newer developments have made it possible to produce bevel gears with straight or hel

7、ical teeth. Rotation of the die (luring penet</p><p>　　Open-die forging is distinguished by the fact that the metal is never completely confined as it is shaped by various dies. Most open-die forgings are pr

8、oduced on flat, V, or swaging dies. Round swaging (lies and V dies are used in pairs or with a flat die. The top (lie is attached to the ram of the press, and the bottom die is attached to the hammer anvil or, in the cas

9、e of press open-die forging, to the press bed.</p><p>　　As the workpiece is hammered or pressed, it is repeatedly manipulated between the dies until hot working forces the metal to the final dimensions, as-s

10、hown in Fig. 1. After forging, the part is rough- and finished-machined. As an example of the amount of material allowed for machining, a 6.5 in. diameter shaft would have to be forged to 7.4 in. dianieter. </p>&

11、lt;p>　　In open-die forging of steel, a rule of thumb says that 50 lb of falling weight is required for each square inch of cross section.</p><p>　　Impression-die Forging</p><p>　　In the simpl

12、est example of impression-die forging, two dies are brought together, and the workpiece undergoes plastic deformation until its enlarged sides touch the side walls of the die (Fig. 2). A small amount of material is force

13、d outside the die impression, forming flash that is gradually thinned. The flash cools rapidly and presents increased resistance to deformation, effectively becoming a part of the tool, and helps build up l)ressUre insid

14、e the bulk of the work- piece that aids material</p><p>　　Closed-die forgings, a special form of impression-die forging, does not depend on the formation of flash to achieve complete filling of the (lie. Thu

15、s closed-die forging is considerably more demanding on die design. Since pressing is often completed in one stroke, careful control of the workpieee volume is necessaiy to achieve complete filling without generating extr

16、eme pressures in the dies from overfilling. Extrusion Forging</p><p>　　As with upsetting, extrusion forging is often accomplished by cold working. Three principal types of metal displacement by plastic flow

17、 are involved. Backward and forward, tube, and impact extrusion are shown in Fig. 3. The metal is placed in a container and corn- pressed by a ram movement until pressure inside the metal reaches flow-stress levels. The

18、workpiece completely fills the container, and additional pressure causes it to leave through an orifice and form the extruded product. </p><p>　　Extruded products may be either solid or hollow shapes. Tube e

19、xtrusion is used to produce hollow shapes such as containers and pipes. Reverse-impact extrusion is used for mass production of aluminum cans. The ram hits a slug of metal in the die at high impact, usually 15 times the

20、yield strength of the metal, which causes it to flow instantaneously up the walls of the die. Other common hollow extrusion products are aerosol cans, lipstick cases, flashlight cases, and vacuum bottles. Secondary ope&l

21、t;/p><p>　　The reduction of the cross section obtainable in one pass is limited by the tendency of the material to spread and form an undesirable flash that may be forged into the surface as a defect in the sub

22、sequent operations. The workpiece is int roduced repeatedly with rota- tion between passes. Ring Rolling</p><p>　　Ring rolling offers a homogeneous circumferential grain flow, ease of fabrication and machi

23、ning, and versatility of material size . Manu- facture of a rolled ring starts with a sheared blank, which is forged to a pancake, punched, and pierced. There is no limit to the size of the rolled rings, ranging fro

24、m roller-bearing sleeves to Fig. 4 Roll forging rings 25 ft in diameter with face heights of 80 in. Various profiles may be rolled by suitably shaping the driven, idling rolls. </p><p>　　CAD/CAM in Forging

25、 CAD/CAM is being increasingly applied to frging. Using the three-dimensional description of a machined part, which may have been computer designed, it is possible to generate the geometry of the associated forging. T

26、hus the forging sections can be obtained from a common (laiR base. Using well-known techniques, forging loads and stresses can be obtained and flash dimensions can be selected for each section where metal flow is approxi

27、mated as ro dimensional (plane strain or</p><p>　　A.2 HEAT TREATMENT OF METAL</p><p><b>　　Annealing</b></p><p>　　The word anneal has been used before to describe heat-t

28、reating processes for softening and regaining ductility in connection with cold working of material. It has a similar meaning when used in connection with the heat treating of allotropic materials. The purpose of full an

29、nealing is to decrease hardness, increase ductility, and sometimes improve machinability of high carbon steels that might otherwise be difflcult to cut. The treatment is also used to relieve stresses, refine grain size,

30、and p</p><p>　　The procedure for annealing hypoeutectoid steel is to heat slowly to approximately 60 above the Ac3 line, to soak for a long enough period that the temperature equalizes throughout the materia

31、l and homogeneous austenite is formed, and then to allow the steel to cool very slowly by cooling it in the furnace or burying it in lime or some other insulating material. The slow cooling is essential to the precipitat

32、ion of the maximum ferrite and the coarsest pearlite to place the steel in its softest, </p><p>　　The purpose of normalizing is somewhat similar to that of annealing with the exceptions that the steel is not

33、 reduced to its softest condition and the pearlite is left rather fine instead of coarse. Refinement of grain size, relief of internal stresses, and improvement of structural uniformity together with recovery of some duc

34、tility provide high toughness qualities in normalized steel. The process is frequently used for improvement of machinability and for stress nlief to reduce distortion that</p><p>　　Minimum hardness and maxim

35、um ductility of steel can he produced by a process called spheroidizing, which causes the iron carbide to form in small spheres or nodules in a ferrite matrix, in order to start with small grains that spheroid ize more r

36、eadily, the process is usually performed on normalized steel. Several variations of processing am used, but all reqllin the holding of the steel near the A1 temperature (usually slightly below) for a number of hours to a

37、llow the iron carbide to form on i</p><p>　　The main need for the process is to improve the machinability quality of high carbon steel and to pretreat hardened steel to help produce greater structural unifor

38、mity after quenching. Because of the lengthy treatment time and therefore rather high cost, spheroidizing is not performed nearly as much as annealing or normalizing. Hardening of Steel Most of the heat treatment h

39、ardening processes for steel are basel on the production of high pereentages of martensite. The first step. therefore</p><p>　　High temperature gradients contribute to high stresses that cause distortion and

40、 cracklug, so the quench should only as extreme as is necessary to produce the desired structure. Care must be exercised in quenching that heat is removed uniformly to minimize thermal stresses. For example, a long slend

41、er bar should be end-quenched, that is, inserted into the quenching medium vertically so that the entire section is subjected to temperature change at one time. if a shape of this kind were to be quen</p><p>

42、;　　A similar process performed at a slightly higher temperature is called austempering. In this case the steel is held at the bath temperarnre for a longer period, and the result of the isothermal treatment is the format

43、ion of bainite. The bainite structure is not as hard as the martensite that could be formed from the same composition, but in addition to reducing the thermal shock to which the steel would be subjected under normal hard

44、ening procedures, ii is unnecessary to perform any further trea</p><p><b>　　Tempering</b></p><p>　　A third step usually required to condition a hardened steel for service is temperin

45、g, or as it is sometimes referred to, drawing. With the exception of austempered steel, which is frequently used in the as-hardened condition, most steels are not serviceable “as quenched”. The drastic cooling to produce

46、 martensite causes the steel to be very hard and to contain both macroscopic and microscopic internal stresses with the result that the material has little ductility and extreme brittleness. Reduct</p><p>　　

47、In commercial tempering the temperature range of 25O-425 is usually avoided because of an unexplained embrittlement, or loss of ductility, that often occun with steels ternpered in this range. Certain alloy steels also d

48、evelop a ¡°temper brittleness¡± in the tempera- ture range of 425-600, particularly when cooled slowly from or through this range of temperature. When high temperature tempering is necessary for these

49、 steels, they are usually heated to above 600 and quenched for rapid cooling. Qu</p><p><b>　　附錄B 漢語(yǔ)翻譯</b></p><p><b>　　B.1 鍛造</b></p><p>　　金屬變形方法有多種，比如通過(guò)鍛造、滾壓

50、或擠壓，使金屬的塑性流動(dòng)或加工受到控制而得到有用的形狀。這些方法中最廣為人知的是鍛造，它通過(guò)壓力、沖擊或兩者的組合使材料變形。錘鍛 錘鍛是用大的半自動(dòng)鍛錘鍛打熱金屬，如果不用模具，鍛造主要取決于操作者的技巧。如使用封閉?；蛐颓荒?，對(duì)幾個(gè)模膛的每一個(gè)模膛都要錘打一次。同樣地，生產(chǎn)率和質(zhì)量在很大程度上取決于錘鍛操作者的技巧和所用工具。</p><p><b>　　鍛壓</b></

51、p><p>　　鍛壓具有緩慢加壓的特點(diǎn)，同樣可用開(kāi)模或封閉模。開(kāi)模主要用于大型的形狀簡(jiǎn)單的零件，鍛壓后再加工成形。封閉模鍛造很少依賴操作者的技巧，而更多地取決于預(yù)成形模和鍛模的設(shè)計(jì)。例如，目前能用直齒或螺旋齒加工錐齒輪，加工過(guò)程中旋轉(zhuǎn)的模具用螺旋齒擠壓出錐齒輪。</p><p>　　開(kāi)模鍛 開(kāi)模鍛的顯著特征是：用不同模具成形時(shí)，金屬?zèng)]有被完全限制。大多數(shù)開(kāi)模鍛使用平砧、V 形砧或U 型

52、砧模一圓形砧和V 形砧成對(duì)使用或和一個(gè)平砧一起使用，上模裝在壓力機(jī)的壓頭上，下模裝在錘砧上，開(kāi)模壓力鍛時(shí)裝在壓力機(jī)床身上。 錘鍛或壓鍛時(shí)，將工件在模具間重復(fù)鍛打，直至金屬達(dá)到最終尺寸，如圖l 所示。鍛打后，零件再粗加工和精加工，作為一個(gè)加工余量的實(shí)例，一根直徑6 . 5 英寸的軸的鍛打直徑為7 . 4 英寸。 在鋼的開(kāi)模鍛中，一個(gè)經(jīng)驗(yàn)數(shù)據(jù)是每平方英寸橫截面需50 磅鍛擊力。</p><p><

53、;b>　　型腔模鍛</b></p><p>　　型腔模鍛的最簡(jiǎn)單實(shí)例是，將兩個(gè)模具相互靠攏，其間的工件經(jīng)受塑性變形直至其周邊充滿模具為止（圖2 ）。少量材料被壓出型模膛，形成薄薄的飛邊。飛邊迅速冷卻，增加了變形阻力，變成了模具的一部分，幫助在工件內(nèi)部產(chǎn)生壓力，使材料流至未填充的型腔。</p><p>　　封閉模鍛是一種特殊的型腔模鍛，不依賴飛邊的形成，叮完整充填模具。因此

54、，封閉模鍛更多地依賴于模具設(shè)計(jì)。因壓鍛經(jīng)常在一次沖程中完成，因此應(yīng)仔細(xì)控制工件體積，做到既能完全充填，在模具中又不產(chǎn)生多余壓力，使材料滋出。擠壓鍛造</p><p>　　如同冷墩，擠壓常通過(guò)冷加工完成。擠壓鍛主要有三種形式的金屬塑性流動(dòng)，即正與反擠壓、管擠壓和沖擊擠壓，如圖3 所示：將金屬置于容器中，通過(guò)壓頭移動(dòng)加壓直至金屬內(nèi)部壓力達(dá)到流動(dòng)應(yīng)力。金屬完全填滿容器，進(jìn)一步加壓導(dǎo)致金屬通過(guò)小孔流出，形成擠壓產(chǎn)品。

55、 擠壓產(chǎn)品既可以是實(shí)心件也可以是空心件。管擠壓用來(lái)制造空心產(chǎn)品，如容器和管道。反向沖擊擠壓用于鋁罐的大批量生產(chǎn)，壓頭高速?zèng)_擊模具中的金屬原料，通常，應(yīng)力是金屬屈服強(qiáng)度的巧倍，這使金屬瞬間成形。其他常用的空心擠出產(chǎn)品是氣霧罐，唇膏筒，電筒殼和真空瓶，它們經(jīng)常需要進(jìn)一步的加工，比如卷邊，螺紋滾壓，做出波紋和機(jī)加工來(lái)完成產(chǎn)品制作。</p><p>　　通常，鋼的沖擊限制在沖頭直徑的2 . 5 倍以內(nèi)。由于行程長(zhǎng)度

56、、速度等其有較大的變化范圍及其他經(jīng)濟(jì)優(yōu)點(diǎn)，液壓機(jī)用于載荷超過(guò)2000噸場(chǎng)合。公差隨材料和設(shè)計(jì)而變，但生產(chǎn)上通常需要0.002——0.005 英寸的公差.</p><p><b>　　輥軋鍛造</b></p><p>　　最簡(jiǎn)單的輥軋鍛造是將· 根加熱的棒通過(guò)一對(duì)軋輥，使其沿長(zhǎng)度方向變形（圖8 一4 ）與傳統(tǒng)棍軋過(guò)程相比，輥軋鍛造的軋輥直徑較小，相當(dāng)于安裝鍛打

57、工具的心軸。工具的工作表面只占軋輥圓周的一部分（通常一半），來(lái)容納棒料的整個(gè)橫截面。 棒料輥鍛一次的橫截面減少量受到材料擴(kuò)展和形成不必要的毛邊的限制，毛邊可能被壓進(jìn)鍛件表面，在后續(xù)操作中形成缺陷，，工件每重復(fù)送進(jìn)軋輥一次，都要轉(zhuǎn)90度。環(huán)狀軋制 環(huán)狀軋制可得到均質(zhì)的周向纖維流，易于制造和加工，可用于多種尺寸。要將原材料制成一個(gè)，先要卜料，鍛成盤形，再?zèng)_孔和貫穿。 對(duì)環(huán)型坯料的尺寸沒(méi)有限制，小至軸承套，大到直徑2

58、5 英尺、面高8 0英寸的圓環(huán)。適當(dāng)?shù)爻尚伪粍?dòng)軋輥和空轉(zhuǎn)軋輥可軋制出不同輪廓的制品。鍛造中的CAD/CAM CAD/CAM 已日益應(yīng)用于鍛造之中。利用計(jì)算機(jī)設(shè)計(jì)的被加工零件的三維描述，就能生成相關(guān)鍛件的幾何形狀。因此，鍛件橫截面叮通過(guò)一個(gè)通用數(shù)據(jù)庫(kù)獲得。使用眾所周知的方法，可獲得鍛擊力和應(yīng)力，對(duì)每種截面可選擇飛邊尺寸，這里金屬的流動(dòng)近似為二維（平面應(yīng)變和軸對(duì)稱）。對(duì)相對(duì)簡(jiǎn)單的截面形狀，可用計(jì)算機(jī)仿真來(lái)評(píng)價(jià)對(duì)</p>

59、<p>　　B.2 金屬的熱處理</p><p><b>　　退火</b></p><p>　　在前面描述冷拔加工材料的軟化并重新獲得塑性的熱處理方法時(shí)，就已經(jīng)用退火這個(gè)詞。當(dāng)用于同素異晶材料的熱處理時(shí)，該詞具有相似的意義。完全退火的目的是降低硬度、增加塑性，有時(shí)也提高高碳鋼的切削加工性，否則這種鋼很難加工。這種熱處理方法也用來(lái)減少應(yīng)力，細(xì)化晶粒，提高整

60、個(gè)材料的結(jié)構(gòu)均勻性。 退火不總是能提高切削加工性，切削加工性一詞用來(lái)描述幾個(gè)相關(guān)因素，包括材料切削時(shí)獲得好的表面光潔度（即較小的表面粗糙度值― 譯者）的能力。，當(dāng)完全退火時(shí)，普通低碳鋼硬度較低，強(qiáng)度較小，對(duì)切削的阻力較小，但通常由于塑性和韌性太大以致切屑離開(kāi)工件表面時(shí)會(huì)劃傷表面，工件表面質(zhì)量比較差，導(dǎo)致較差的切削加工性。對(duì)這類鋼，退火可能不是最合適的處理方法。許多高碳鋼和大多數(shù)合金鋼的切削加工性通?？山?jīng)退火大大改善，因?yàn)槌谧钴?/p>

61、條件下，它們的硬度和強(qiáng)度太高而不易加工。 亞共析鋼的退火方法是將鋼緩慢加熱到Ac3 線以上大約60 ℃ ，保溫一段時(shí)間，使整個(gè)材料溫度相同，形成均勻奧氏體，然后隨爐或埋在石灰或其他絕緣材料中緩慢冷卻。要析出粗大鐵素體和珠光體，使鋼處于最軟、最韌和應(yīng)變最小的狀態(tài)，必須緩慢冷卻。正火 </p><p><b>　　回火 </b></p><p>　　調(diào)整

62、淬硬鋼以便使用的第三步通常是回火。除了等溫淬火鋼通常在淬火狀態(tài)下使用外，大多數(shù)鋼都不能在淬火狀態(tài)下使用。為產(chǎn)生馬氏體而采取的激冷使鋼很硬，產(chǎn)生宏觀內(nèi)應(yīng)力和微觀內(nèi)應(yīng)力，使材料塑性很低，脆性極大。為減少這種危害，可通過(guò)將鋼再加熱到線（低溫轉(zhuǎn)變）以下某一溫度。悴火鋼回火時(shí)產(chǎn)生的結(jié)構(gòu)變化是時(shí)間和溫度的函數(shù)，其中溫度是最重要的。必須要強(qiáng)調(diào)，回火不是硬化方法，而是剛好相反?；鼗痄撌菍⒔?jīng)熱處理硬化的鋼，通過(guò)回火時(shí)的再加熱，來(lái)釋放應(yīng)力、軟化和提高塑性。

63、 回火引起的結(jié)構(gòu)變化和性能改變?nèi)Q于鋼重新加熱的溫度。溫度越高，效果越大，所以溫度的選擇通常取決于犧牲硬度和強(qiáng)度換取塑性和韌性的程度、重新加熱到100 ℃ 以下，對(duì)淬火普碳鋼影響不大，在100 ℃ 到200 ℃ 之間，結(jié)構(gòu)會(huì)發(fā)生某些改變，在200 ℃ 以上，結(jié)構(gòu)和性能顯著變化。在緊靠著溫度以下的長(zhǎng)時(shí)間加熱會(huì)產(chǎn)生與球化退火過(guò)程類似的球化結(jié)構(gòu)。 在工業(yè)上，通常要避免在250 ℃ 到425 ℃ 范圍內(nèi)回火，因?yàn)檫@個(gè)范圍內(nèi)回火的