机械设计制造及其自动化专业英语翻译

1、Unit 1 Metals金属The use of metals has always been a key factor in the development of the social systems of man. Of the roughly 100 basic elements of which all matter is composed, about half are classified as metals. The distinction between a metal and a nonmetal is not always clear-cut. The most basi

2、c definition centers around the type of bonding existi ng betwee n the atoms of the element, and around the characteristics of certain of the electrons associated with these atoms. In a more practical way, however, a metal can be defi ned as an eleme nt which has a particular package of properties.M

3、etals are crystalline when in the solid state and, with few exceptions (e.g. mercury), are solid at ambient temperatures. They are good con ductors of heat and electricity and are opaque to light. They usually have a comparatively high density. Many metals are ductile-that is, their shape can be cha

4、nged permanently by the application of a force without break ing. The forces required to cause this deformation and those required to break or fracture a metal are comparatively high,在人类社会的开展中，金属的应用 起着关键性的作用。构成物质的大约100种根本兀素中，大约有一半为金属。金属和非 金属之间的区别不是特别明显。最根本的定 义集中在元素原子间存在的连接形式和与这 些原子相关联的电子的某些特性。然而，在 实

5、际应用中，可以将具有某些特性集合金属 定义为某种元素。除了少数例外金属在常温下是固态 的。它们是热和电的良导体，不透光。它们 往往具有较咼的密度。 许多金属具有延展性， 也就是说，在不被破坏的情况下它们的形状 在外力的作用下可以发生变化。引起永久变 形所需的力和最终使金属断裂所需的力相当 大，尽管发生断裂所需的力远没有像所预期 的撕开金属原子所需的力那么大。从我们的观点来看，在所有的特性中结 晶性是最重要的。结晶体是这样一种结构， 组成它的原子定位在规那么的三维排列中，仿 佛位于三维棋盘的方格的角上。原子间距随 着原子大小呈规律性变化，原子间距是金属 的一种特性。三维排列的轴线决定了晶体在 空

6、间中的方向。在工程实践中应用的金属由 大量的晶体组成，这些晶体称之为晶粒。在 大多数情况下，晶粒在空间中是自由排列的。 在原子范围内，晶粒之间相互接触紧密结合。 晶粒之间连接区域被称为晶界。although, the fracture forces is not nearly ashigh as would be expected from simplecon siderati on of the forces required to tear apartthe atoms of the metal.One of the more significant of these characteri

7、stics from our point of view is that of crystalli nity A crystalline solid is one in which the constituent atoms are located in a regular three-dimensional array as if they were located at the corners of the squares of a three-dimensional chessboard The spaci ng ofthe atoms in the array is of the sa

8、me order as the size of the atoms, the actual spaci ng being a characteristic of the particular metal. The direct ions of the axes of the array defi ne the orientation of the crystal in space. The metalscommonly used in engineering practice are composed of a large number of such crystals, called gra

9、ins. In the most general case, the crystals of the various grains are randomly orie nted in space. The grains are everywhere in in timate con tact with one ano ther and joined together on an atomic scale. The region at which they join is known as a gra in boun dary.An absolutely pure metal (i.e. one

10、 composed of only one type of atom) has n ever bee n produced. Engin eers would not be particularly interested in such a metal even if it were to be produced, because it would be soft and weak. The metals used commercially inevitably contain small amounts of one or more foreign elements, either meta

11、llic or nonmetallic. These foreign elements may be detrimental , they may be beneficial, or they may have no in flue nee at all on a particular property. If disadva ntageous, the foreig n elements tend to be known as impurities . If advantageous, they tend to be known as allo yingeleme nts. Allo yin

12、geleme nts arecommonly added deliberately in substantial amounts in engineering materials. The result is known as an alloy.The distinction between the descriptors metal and alloy is not clear-cut. The term metal may be used to encompass both a commercially pure metal and its alloys. Perhaps 计 can be

13、 said that the more deliberately an allo ying additi on has bee n made and the larger the amount of the addition, the more likely it is that the product will specifically be called an alloy. In any event, the chemical composition of a metal or an alloy must be known and con trolled within certa in l

14、imits if con siste nt performa nee is to be achieved in service. Thus chemical compos it ion has to be taken into绝对纯洁的金属从来也没有被生产出来 过。即使绝对纯洁的金属可以生产出来，工 程师们对它们也并不会特别感兴趣，因为它 们很柔软、脆弱。实际应用中的金属往往都 包含着一定数量的一种或多种外来金属或非 金属元素，这些外来元素可能是有害的也可 能是有益的或者它们对某种特定的属性没有 影响。如果是有害的，这些外来元素被认为 是杂质。如果是有益的，它们被认为是合金 元素。在工程材料中

15、往往被特意地参加一定 数量的合金元素。得到的物质被叫做合金。金属和合金区别不大。金属这个词可以 包括工业用纯金属和它的合金。也许可以这 样说，合金元素越成心的被添加，被添加的 合金元素的量越大，那么生产出来的产品越 倾向于被称之为合金。不管怎样，如果想使 一种金属或合金在使用中表现出稳定一致的 特性，在其中添加何种化学成分，它的量多 大都应该在控制范围之内。因此，当想了解 决定金属和合金性质的因素时，应充分考虑 它们的化学组成。在50种左右的金属兀素里， 工程头践中 只有少数金属被大量生产和使用。到目前为account when developing an understanding ofth

16、e factors which determine the properties ofmetals and their alloys.Of the 50 or so metallic elements, only a few are produced and used in large qua ntities inengin eeri ng practice. The most importa nt by far is iron , on which are based the ubiquitous steels and cast irons (basically alloys of iron

17、 and carb on). They acco unt for about 98% by weight of all metals produced. Next in importanee for structural uses (that is, for structures that are expected to carry loads) are aluminum , copper, nickel, and titanium% for all other metals. As might be expected, the rema in ders are all used in rat

18、her special applications. For example, nickel alloys are used principally in corrosion-and heat-resistant applicati ons, while tita nium is used exte nsively in the aerospace industry because its alloys have good comb in ati ons of high stre ngth and low den sity. Both ni ckel and tita nium are used

19、 in high-cost, high-qualityapplications, and,in deed, it is their high cost that tends to restrict their applicati on.We cannot discuss these more esoteric properties here. Suffice it to say that a whole complex of properties in addition to structural止最重要的是铁，以它为根底构成了处处可 见的钢和铸铁。主要由铁和碳构成的合金 它们的重量占所有生产

20、出来的金属重量的 98%。在结构应用也就是说，可以承受载 荷的结构中居于其次位置的是铝、铜、镍 和钛。在所有的金属产量中，铝占0.8%，铜占0.7%，剩下的占0.5%。剩下的金属用于 相对特殊的用途。例如，镍合金主要用于抗 磨损和耐高温的用途，由于钛合金具有高强 度和低密度的综合特性，钛被广泛应用于航 空工业中。镍合钛有咼本钱和咼质量的使用 特性，事实上，它们高的本钱限制了它们的 应用。我们不能在这里讨论这些深奥的特性。 在合金材料被米用和应用于工程实际之前， 掌握其结构强度和它的综合性质就够了。举 例来说，它可以强度很咼，并且有好的耐磨 性；它可以被例如拉伸加工，机械加工，或 焊接等特殊工艺

21、来加工出来；它可以被循环 利用；它的本钱和实用性是首要的。stre ngth is required of an alloy before it will be accepted in to, and survive in. engin eeri ngpractice. It may, for example, have to be stro ng and yet have reas on able corrosi on resista nee; it may have to be able to be fabricated by a particular process such as de

22、ep drawing, machining, or welding; it may have to be readily recyclable; and its cost and availability may be of critical importa nee.Unit 2 Selection of Construction Materials工程材料的选择There is not a great differenee between “ this steel and “ that steel; all are very similar in mecha nical properties

23、. Select ion must be made on factors such as harde nability, price, and availability , and not with the idea that“can do something no other can do because it contains 2 perce nt in stead of 1 perce nt of a certa in alloying element, or because it has a mysterious (神 在钢之间没有太大的区别；所有的钢在机 械性能方面都是近似的。 它们

24、的选取标准是诸 如脆硬性，价格，和可用性等。不仅仅是因为 这种钢含有2%的合金元素另一种钢含有1%:hW使前者ee有了后者没有的某些能力，或者是某种钢具有神奇的名字。经过热处理后，任何 一种钢都具有大范围的特性；这种性质冋样在 合金钢中存在。秘的，不可思议的 n ame. A treme ndous range of properties is available in any steel after heat treatme nt; this is particularly true of alloy steels.Con siderati ons in fabricati on制造The

25、properties of the final part hardness, stre ngth, and mach in ability , rather tha n properties required by forging, govern the selection of material. The properties required for forging have very little relation to the final properties of the material; therefore, not much can be done to improve its

26、 forgeability. Higher-carb on steel is difficult to forge. Large grain size is best if subseque nt heat treatme nt will refine the grain size.关于加工的考虑最后零件的特性硬度、强度和可加工性 而不是锻造特性决定了材料的选择。可锻性与材料的最后特性联系不大；因此，提高金属的可锻造性价值不大。 咼碳钢很难锻造。如果在 随后的热处理过程进行细化， 大尺寸晶粒是最 好的。Low-carb on, n ickel-chromium铬steels are just

27、about as plastic at high temperature under a single 520-ft lb1 ft lb=1.35582J blow as plai n steels of similar carb on content. Nickel decreases forgeability of medium-carb on steels, but has little effect on low-carb on steels. Chromium seems to harden steel at forging temperatures, but vanadium 钒h

28、as no discernible可区分的effect; neither has the method of manufacture any effect on high-carb on steel.在高温下低碳，镍铬合金钢在受到 520-ft lb的冲击下表现出与相冋碳含量普通 钢几乎同样的塑性。镍减少了中碳钢的可锻 性，但对低碳钢影响不大。铬在锻造温度下时使钢硬化，但钒没有明显的效果；两种加工方 法对高碳钢没有影响。FormabilityThe cold-formability of steel is a function功 能of its ten sile stre ngth comb

29、ined with ductility. The tensile strength and yield point must not be high or too much work will be required in bending弯曲;likewise冋样地,the steel must have sufficient充足的 ductility to flow to the required shape without cracking. The force required depends on the yield point, because deformation starts

30、in the plastic range above the yield point of steel. Work-hardening also occurs here, progressively日益增多地 stiffening使 变硬the metal and caus ing difficulty, particularly独特的，显著的in the low-carb on steels.成形钢的冷成形是它的拉伸强度和延展性相结 合的结果。拉伸强度和屈服点不能太高否那么在 发生弯曲时需要做很多工作； 与之相类似，钢 应该有咼延展性，使其在没有断裂的情况下成 形。加工力的大小取决于屈服点，

31、因为钢在屈服点之上才开始变形。 与此同时，加工硬化也 同时发生，金属变得越来越硬，增加加工难度， 尤其在低碳钢中容易发生。It is quite in terest ing in this connection 关于 这一点，就此而论to discover that deep drawscan sometimes be made in one rapid operati on that could not possibly be done leisurely 缓慢地，从 容不迫地in two or three. If a draw is half madeand the n stopped,

32、it may be n ecessary to ann eal退 火before proceeding, that is换句话说，if the在这方面，相当有趣的是你将发现有时可 通过一次快速加载完成大拉伸，但以缓慢的方式两三次加载却不能实现。如果拉伸进行了一 半就停止了，那么在再加工之前应先退火，也 就是说工件是否有时间进行加工硬化。这不是一种科学的表达方法，但确头是发生了。piece is given time to work-harden. This may not be a scientific statement, but it is actually what seems to h

33、appe n.Internal stressesCold forming is done above the yield point in the work-hardening range, so internal stressescan be built up easily. Evidenee of this is the springback回弹 as the work leaves the forming operation and the warpage翘曲，扭曲in any任何一种subseque nt heat treatme nt. Even asimple washer mig

34、ht, by virtue of依靠the internal stresses result ing from pun chi ng冲压and then flattening整平，warp弯曲 severely 严格地，剧烈地duri ng heat treat in g. virtue n.德行，美德，贞操，优点，成效，效力，英勇 believed in the virtue of prayer.相信祈祷的力量内应力在咼于屈服点的加工硬化区进行冷加工很 容易产生内应力。例如工件停止成型加工后会 发生回弹，在随后的热处理后， 工件会发生翘 曲。即使是一个简单的垫圈，由于打孔和随后 的平整加工中

35、产生内应力，也会在热处理中呈现严重的翘曲。When doubt exists as to关于whetherinternal stresses will cause warpage，a piece can be checked by heating it to about 1100 and then letting it cool. If there are internal stresses，the piece is likely to可能deform. Pieces that will warpseverely while being heated have been seen，yet 然而

36、the heat-treater was expected to put them through and bring them out better than they were in the first place.当是否内应力会引起翘曲的疑心存在时， 可以通过将工件加工至1100然后进行冷却来验证。如果存在内应力，工件会发生变形。经 过热处理的工件像我们看到的那样会发生严 重的翘曲，但是我们仍然希望工件被扔到热处 理炉中被处理，这样好过它存在内应力的状 态。Weldi ng%. higher-carb on steel is welded every day，but only with

37、proper preheating. There are two important factors: the amount of heats that is put in ; the rate at which it is removed.焊接不需要预热或之后进行热处理就能平安焊 接的取咼碳含里为 0.3%。咼碳钢通过适宜的 预热通常也可焊接。有两点值得注意：吸收热 量的多少；移除速度。Weldi ng at a slower rate puts in more heat and heats a large volume of metal，so the cooling rate due to

38、 loss of heat to the base metal is decreased减 少.A preheat will do the same thing. For example， sae4150 steel，preheated to 600 or 800, can be welded readily容易地.When the flame or arc is take n away from the weld, the cooli ng rate is not so great, owing to the higher temperature of the surro unding me

39、tal and slower cooli ng results. Even the most rapid air-harde ning 风硬钢 steels are weldable if preheated and welded at a slow rate.低速焊接带来了更多的热量，这对金属的 大量体积进行了加热，所以冷却速度降低。预 热可以取得与之相当的效果。例如当被预热至或 时可以很好的焊接。由于周围金属的较高温度，当焊接弧移开焊接点后， 冷却 速度不会太快，产生了低速冷却的结果。 即使 是冷作硬化速度最快的金属也可以通过预热 和慢速焊接到达良好的焊接效果。Machi nability

40、Mach in ability机械加工性冃能means severalthin gs. To product ion men it gen erally mea ns being可加工性可加工性意味着几件事情。对于加工者来 说，它意味着可以快速的移除金属，取得最好able to remove metal at the fastest rate, leave the best possible fini sh, and obta in the Ion gest possible tool life. Mach in ability applies to应用于thetool-work 工具，零件c

41、omb in atio n.的加工效果，得到最长的刀具寿命。 可加工性 是刀具和零件的结合。It is not determined by hardness硬度 alone, but by the toughness韧性，microstructure,chemical composition成分，and tendency倾 向 of a metal to harden under cold work. In the misleading expression “ tochard to machine the word “ hard is usually meant to be synonymo

42、us 同义的 with “difficult . Many times a mat is actually too soft to mach ine readily. Softn ess and tough ness may cause the metal to tear撕裂 and flow ahead of the cutting tool rather than cut clea nly. Metal that are in here ntly天性地,固有地 soft and tough are sometimes alloyed to improve their mach in abi

43、lity at some sacrifice牺牲inductility. Examples are use of lead 铅 in brass 黄铜and of sulfur硫磺in steel.加工性不仅仅只由硬度决定，它还由韧性，微观结构，化学成分和在冷加工下金属所呈现 的硬化特性所决定。在容易混淆的表示“难加 工中，“ hard与“ difficult 同义。许多时 候，因为材料过软而难于稳定加工。材料柔软性和韧性能够产生金属撕裂，使金属在完成切 e削前流动至刀具前端。柔软的金属往往会被加 入合金从而牺牲它的延展性来提高加工性能。 如黄铜中参加铅钢中参加硫磺。Mach in abili

44、ty is a term used to in dicate the relative比拟的ease不费力with which amaterial can be machined by sharp cutting tools in operations such as turning 车,drilling 钻, milling铳，broaching拉削，and reaming铰.机械加工性能是在指对工件材料使用刀具 进行诸如车、钻、铳、拉削、铰加工时的难易 程度。In the mach ining of metal, the metal being cut, the cutt ing tool

45、, the coola nt, the process and type of machine tool机床，and the cutting conditions all in flue nee the results. By cha nging any one of these factors, different results will be obtained. The criterion 标准upon which the ratinas 等级listed are based等级评定的标准 is the relative在对金属进行加工时，被切削的金属，切 肖U刀具，冷却液，使用的机床的

46、种类，切削条 件均影响着切削效果。改变任何一种均会产生 不同的切削效果。切削效果评定的准那么是：车 削时在固疋的切削条件下产生一疋量的刀具 磨损时，被加工试件相应的材料去除量。volume of various不同种 materials that may beremoved by turning under fixed conditions toJJproduce an arbitrary任意的fixed amount of1J' 1J -tool wear淬透性：指在规定条件下，决定钢材淬硬深度和硬度分布的特性。即钢淬火时得到 淬硬层深度大小的能力，它表示钢接受淬火的能力。钢材淬透性

47、好与差，常用淬硬层深 度来表示。淬硬层深度越大， 那么钢的淬透性越好。 钢的淬透性是钢材本身所固有的属性, 它只取决于其本身的内部因素，而与外部因素无关。钢的淬透性主要取决于它的化学成 分，特别是含增大淬透性的合金元素及晶粒度，加热温度和保温时间等因素有关。淬透 性好的钢材，可使钢件整个截面获得均匀一致的力学性能以及可选用钢件淬火应力小的 淬火剂，以减少变形和开裂。淬透性主要取决于其临界冷却速度的大小，而临界冷却速度那么主要取决于过冷奥氏体的稳定性，影响奥氏体的稳定性主要是：1.化学成分的影响碳的影响是主要的，当C%小于1.2 %时，随着奥氏体中碳浓度的提高，显著降低临界冷却速度，C曲线右移，

48、钢的淬透性增大；当C %大于时, 钢的冷却速度反而升高， C 曲线左移，淬透性下降。其次是合金元素的影响，除钴外，绝大多数合金元素溶入奥氏体后，均使 C 曲线右移，降低临界冷却速度， 从而提高钢的2. 奥氏体晶粒大小的影响 大的奥氏体晶粒能使 C 曲线右移，形、开裂倾向和降低韧性。3. 奥氏体均匀程度的影响核率就越低，转变的孕育期增长，4. 钢的原始组织的影响淬透性。奥氏体的实际晶粒度对钢的淬透性有较大的影响，粗降低了钢的临界冷却速度。 但晶粒粗大将增大钢的变在相同冷度条件下， 奥氏体成分越均匀， 珠光体的形 C 曲线右移，临界冷却速度减慢，钢的淬透性越高。 钢的原始组织的粗细和分布对奥氏体的

49、成分将有重大 影响。5.局部元素，例如 Mn ， Si 等元素对提高淬透性能起到一定作用，但同时也会对钢 材带来其他不利的影响。可锻性 forgeability金属具有热塑性，在加热状态各种金属要求温度不同 ，可以进行压力加工，称为具有可锻性。可锻性：指金属材料在压力加工时，能改变形状而不产生裂纹的性能。它包括 在热态 或 冷态下能够进行锤锻，轧制，拉伸，挤压等加工。可锻性的好坏主要与金属 材料的化学成分有关讨论 元素在钢中的形成物对可锻性的影响1C与Fe形成渗碳体Fe3C,与其它合金元素形成合金渗碳体FeM3C或合金碳化物。所有碳化物都有硬度高、 塑性低、 熔点高的特点， 但渗碳体型碳化物在

50、加热到锻造温度时经 适当保温可大局部或全部溶入固溶体中， 而合金碳化物较难溶入固溶体中， 对钢的可锻性影 响最大。 一般高合金工具钢含碳高， 故具有变形抗力大， 塑性差， 碳化物不易被粉碎等特点。2Mn 在钢中形成 MnS以代替FeS。因MnS熔点高1620C，且呈断续分布，不像 FeS 熔点988C,呈网状分布在晶界，所以可减少热脆。锰对钢的过热性粗晶很敏感，钢锭加热温度过高，易生粗晶，使锻造困难。锰对珠光体 钢的可锻性影响较小，奥氏体锰钢临界点将降低。3 Ni 炼钢时有 Ni 极易吸收氢形成大量气泡，锻造时引起开裂。 Ni 与 Mn 的作用相反， 它促使硫化物成网状分布于晶界，使锻造时开裂

51、，所以不宜在含硫的炉气中加热。珠光体 Ni 钢在锻造时易形成片状破裂和带状组织。为了消除这种组织可采用镦粗和拔长交错进行，或在10001100 C下长时期扩散退火。4 Cr 铬在钢中形成较稳定的碳化物，提高碳化物在钢中的溶解温度，减慢溶解速度。 铬能促进使铸锭生成大晶粒，冷却时沿晶界形成内裂。高铬钢在空气中冷却即能淬火，常在外表生裂，所以不易锻造。5 V与碳形成稳定碳化物V 能使钢生成细晶组织，阻止过热，适当参加对锻性有利。6 Mo 钼的熔点高，能降低钢的过热倾向它和 Ni 一样，使硫化物以网状分布在晶界。 含有 0.7%C， 25%Mo 的钼钢，锻造时无特殊困难。这些钢在空冷时间淬火，要防止

52、冷裂。Mo 提高钢的热强性，提高变形抗力。7 W 与碳形成稳定的碳化物 提高钢的热强性，增大变形抗力8 Cu 铜在钢中可溶于铁素体中，也可沿晶界析出游离铜铜中含0.15%Cu时，加热不当，外表易生裂纹，高温轧制时易产生热脆9 B硼能细化晶粒，能溶解在丫和a固溶体中，与Fe化合成Fe2B钢中含B > 0.007%时，锻造易裂10 S在钢中形成硫化物或共晶体，如FeS、Fe的熔点为985C,且成网状布于晶界显著降低可锻性红脆11 P促成偏析，使晶粒粗大，容易引起锻件外表龟裂降低可锻性Unit 3 Mecha ni cal Properties of MaterialsThe material

53、properties can be classifiedinto three major headi ngs:(i) Physical, (ii) Chemical,(iii) Mecha ni cal.Physical propertiesDen sity or specificgravity, moisture content,etc., can be classified underthis category.Chemical properties Many chemical properties come un der this category. These in clude aci

54、dity or alkali nity, reactivity and corrosi on.The most importa nt of材料特性主要分为三类：(i)物理特性，(ii)化学特性，(iii)力学性能。物理特性密度或特定的重力，湿 度等都属于此范畴。化学特性许多化学特性都归入到 这个范畴。其中包括酸性 或碱性，活性和耐腐蚀性。 而在这其中最重要的是耐 腐蚀性，通俗的解释是材 料在特定大气中长期使用 时，抵抗腐蚀的能力。these is corrosi on which can be expla ined inlayman ' s terms as the resistanc

55、e of the material to decay while in continu ous use in a particular atmosphere.Mecha ni cal properties Mecha ni cal properties in clude the stre ngth properties like ten sile, compressi on, shear torsi on, impact, fatigue and creep. The ten sile stre ngth of a material is obtai ned by dividi ng the

56、maximum load, which the specime n bears by the area of cross-section of the specime n.This is a curve plotted betwee n the stress力学特性力学特性包括诸如拉 伸，压缩，剪切，扭转， 冲击，疲劳和蠕变等强度 特性。一种材料的拉伸强 度由试件承载的最大载何 除以试件的横截面积得 至叽7如下列图为在拉伸试验中 沿着X轴横轴的应变 和沿着丫轴纵轴的应 力之间的关系曲线。材料 在加载时，随着载荷大小 的变化，尺寸会发生改变。 当卸载时，变形消失。对 于许多材料来说，上述情 况发

57、生的应力极限值称为 弹性极限。在应力-应变曲along the Y-axis(ord in ate) and the stra in along the X-axis(abscissa) in a ten sile test. A material tends to cha nge or cha nges its dime nsions whe n it is loaded, depe nding upon the magn itude of the load.Whe n the load is removed it can be see n that the deformati on disappear s. For many materials this occurs up to a certain value线中，直线关系和随后的 小小的弯曲描述了上述的 加载和卸载。!在弹性范围内，应力应 变成比例的应力极限值称 为比例极限。在这个区域 中，金属服从胡克定律一 阐述了在加载的弹性范围 内，应力和应变成比例关 系材料在卸载后，能够 完全回复它原来的尺寸。 在曲线的实际绘制中，比 例极限值要稍微比弹性极 限值低。这可能是由于材 料回复原尺寸需要的时间 延迟。这种现象在一些有 色金属中常常出现。of the stress called the elastic limit-Th