锻造铸造焊接外文翻译

1、毕业设计(论文)外文翻译学生姓名： 系 别： 机 械 工 程 系专 业： 机械设计制造及其自动化班 级： 学 号: 译文出处：Science and Technology Engl-ish for Mechanical EngineeringCasting、Forging and Welding1. CastingMetal casting is one of the oldest of all industries, both ancient and medieval history offering examples of the manufacture and use of castin

2、g. From simple axeheads poured from copper in open moulds some 5000 years age, casting in the pre-Christian world developed to a point at which elaborate bronze statuary could be produced in two-piece and cored moulds. By the end of the medieval period, decorated bronze and pewter casting had begun

3、to be used in European church and domestic life. The widespread adoption of cast iron as engineering material awaited the success of Abraham Darby in 1790 in smelting in the coke blast furnace; this paved the way for the massive use of cast iron in construction during the years following the industr

4、ial revolution.Many foundries sprang up after the industrial revolution, the vast majority being for the manufacture of the cast iron then being used as a structural material. The quantity production of iron castings in the nineteenth century was not matched by a universal advance in quality and the

5、 engineering use of the products encountered more serious risks in a non-ductile material.Despite the skill of the molder in producing complex forms, there was little change in the metallurgical and engineering situation until the modern era brought a better understanding of the factors determining

6、quality. With modern techniques of process control the rudimentary judgment of the operator could give way to objective measurements of metal temperature, molding material properties and other production variables. These improvements have been applied not only to cast iron but to a wide range of cas

7、t alloys.There are four basic casting methods: sand-casting, die-casting, investment-casting, and centrifugal casting.Sand-casting is the most widely used method employed in foundry. In this process, sand moulds are contained in metal molding boxes that have four sides but no top or bottom. During t

8、he molding operation the boxes are located together by pins so that they can be separated to remove the pattern, and replaced in the correct position before the metal is poured in. The boxes are clamped together, or the cope (top section) weighted down when pouring to prevent the cope from “floating

9、 away” from the drag (lower section) when the mould is full of molten metal. The sequence when molding the simple two-part mould to cast a bracket is illustrated as follows.At the first stage the pattern is seated on the moulding board. The pattern is covered with facing sand, which is a specially p

10、repared sand of good quality, which can take a clean and smooth impression, and can resist the heat from the molten metal that will be in contact with it. The facing sand is backed up with molding sand, which is old facing sand from previous moulds. The molding sand is carefully rammed up so that it

11、 is fairly tight around the pattern to produce a good solid mould, yet permeable enough to allow the gases produced during casting to escape. The sand is finally leveled off.At the second stage the mould with the pattern still in position is inverted; the exposed sand lightly covered with parting sa

12、nd, and the exposed pattern with facing sand.(The parting sand has no cohesion, and is introduced to permit a clean separation when the mould is opened up to remove the pattern .) The second molding box is located in position on the first box and filled with molding sand. Two or more plugs are intro

13、duced when the second box is being filled (these are removed later, leaving channels in the sand). One of these plugs is positioned to one side of the pattern. The sand is rammed up and leveled off.Now, at stage 3, to allow the pattern to be removed. This is done by screwing a bar with a threaded en

14、d into a suitable insert in the pattern, damping the sand around the pattern, and gently rapping the bar in all directions so that the pattern can be carefully withdrawn. To facilitate the removal of the pattern without scuffing the sides of the impression, all surfaces that lie in the direction of

15、pattern removal are inclined slightly by a small amount (the draw angle).A groove called a gate is cut in the sand face to allow the channel produced by the plug that is outside the pattern to connect with the impression .The metal is poured through this channel (called the runner), and the gate pre

16、vents it from dropping straight into the impression and damaging it .The cross-section of the gate is slightly smaller than that of channel so that a full runner will always supply metal to the gate at a slight pressure.Finally, the mould is reassembled, carefully locating and securing the two secti

17、ons. The top section is known as the cope, and the lower section is known as the drag. The sand in the cope is vented. These vents allow the sand to be rammed up more tightly at the earlier stages without the risk of gases being trapped in the molten metal and forming blowholes in the solid metal. A

18、 sand-feeding gate (also called a pouring or bowl) is added to make it easier to pour the metal into the runner. The molten metal is poured through the runner and the air will escape through the riser.The impression will be filled with molten metal when it is completely filled. Gases can escape thro

19、ugh the runner and the riser, which also act as headers to supply the impression with more metal to compensate for the contraction of the metal when cooling in the molten state. 2. ForgingForging is the plastic working of metal by means of localized compressive forces exerted by manual or power hamm

20、ers, presses, or special forging machines. It may be done either hot or cold. however, when it is done cold, special names usually are given to the processes. Consequently, the terms“forging” usually implies hot forging done above the recrystallization temperature.Modern forging is a development for

21、m the ancient art practiced by the armor makers and the immortalized village blacksmith. High-powered hammers and mechanical presses have replaced the strong arm, the hammer, and the anvil and modern metallurgical knowledge supplements the art skill of the craftsman in controlling the heating and ha

22、ndling of the metal.Forge ability is the term used in the industry to denote a material relative resistance to deformation and its plasticity. While considerable disagreement exists as to precisely what characteristics the word “forge ability” should include, the term as used here is defined as the

23、tolerance of a metal or alloy for deformation without failure, regardless of forging pressure requirements.Raw material used for forging is generally bar or billet stock hot rolled from ingots melted in open-hearth, electric arc, or vacuum arc furnace .other forms and shapes such as rolled slabs, pl

24、ats, and stock produced by continuous casting techniques are occasionally used .for certain grades ,vacuum arc melting imparts better forge ability than does conventional arc melting . However, the major purpose of vacuum melting is the improvement of mechanical properties and cleanliness, not forgi

25、ng behavior.Equipment behavior influences the forging progress since it determines the feasibility of forging a part and affects the rate of deformation and the temperature conditions.The hammer is the most economical type of equipment for generating load and energy necessary to carry out a forging

26、process, provided that the material being forged can support high deformation velocities. It is most commonly used hot forging equipment for repeated blows on the same workpiece and cannot be overloaded.There are various types of hammers: air-lift gravity drop hammers, power drop hammers, power drop

27、 hammers, Counterblow hammers ect. In a simple gravity drop hammer the upper ram is positively connected to a board, a belt, a chain or a piston. When forging the ram is lifted to a certain height and then dropped on the stock placed on the anvil. During the down stroke, the rain is accelerated by g

28、ravity and builds up the blow energy. The upstroke takes place immediately after the blow, the force necessary to ensure quick lift-up of the ram can be 3 to 5 times the ram weight. The operation principle of a power-drop hammer is similar to that of an air drop hammer. During the down stroke, in ad

29、dition to gravity, the ram is accelerated by steam, cold air or hot air pressure. In an electro hydraulic gravity-drop hammer, the ram is lifted with oil pressure against an air cushion. The compressed air slows down the upstroke of the ram and contributes to its acceleration during the down stroke

30、.thus; the electro hydraulic hammer also has a minor power hammer action.Press forging employs a slow squeezing action in deforming the plastic metal, as contrasted with the rapid-impact blows of a hammer. Hydraulic forging press is operated by large pistons driven by high-pressure hydraulic or hydr

31、ometric system. The squeezing action is carried completely to the center of the part being pressed, thoroughly working the entire section. These presses are the vertical type and may be either mechanically or hydraulically operated. The mechanical presses, which are faster operating and most commonl

32、y used, range in capacity from 5000 to 10000 tons.In the forging press a grater proportion of the total work put into the machine is transmitted to the metal than in a drop hammer. The machine and foundation absorb much of the impact of the drop hammer .press reduction of the metal is faster, and th

33、e cost of operation is consequently lower. most press forging s are symmetrical in shape ,having surfaces, which are quite smooth, and provide a closer tolerance than is obtained by a drop hammer .however ,drop forging can forge many parts of irregular and complicated shapes more economically. Forgi

34、ng presses are often used for sizing operations on parts made by other forging processes.For small forgings closed impression dies are used, and only one stroke of the ram is normally require to perform the forging operation .the maximum pressure is built up at the end of the stroke ,which forces th

35、e metal into shape .dies may be mounted as separate units, or all the cavities may be put into a single block. for small forgings individuals die units are more convenient .large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press

36、goes deeper. Further, the press can take a cooler ingot and can work to closer dimensions.The forging should be done at about the same temperature as rolling; the process improves the physical properties of the steel just as rolling does. In the final forging it is important not to have the steel to

37、o hot, for overheated steel will have poor mechanical properties when cooled. in heating for forging the temperature is usually judged by the eye, but where a large number of the same patterns will be made, the pieces to be forged are heated in furnaces in which the temperature is indicated by pyrom

38、eters, and often is automatically controlled.3. weldingWelding techniques have become so versatile that it is difficult nowadays to define “welding”. Formerly welding was “the joining of metals by fusion”, that is, by melting, but this definition will no longer do. Welding was next defined as the “j

39、oining of metals by heat”, but this is not a proper definition either. Not only metals can be welded, so can many of the plastics. Furthermore several welding methods do not require heat. Every machinist is familiar with heatless welding method under some circumstances. Besides these, we can weld wi

40、th sound and even with the famous laser. Faced with a diversity of welding methods that increase year by year, we must here adopt the following definition of welding: welding is the joining of metals and plastics by methods that do not employ fastening devices”.There is also no uniform method of nam

41、ing welding processes. Some processes are named according to the heat source or shielding method, other certain specialized processes are named after the type of joint produced. Examples are spot and butt welding. But an overall classification can not take account of this because the same type of jo

42、int may be produced by a variety of processes. Spot welding may be done by electric resistance, arc, or electron-beam processes and butt welding by resistance, flash or any of a number of other methods. Many welding processes are named depending on the heat applied, equipment used, and type of metal

43、 to be joined and the strength of the joint.Soldering is the process of joining two metals by a third metal to be applied in the molten state. Solder consists of tin and lead, while bismuth and cadmium are often included to lower the melting point. One of the important operations in soldering is tha

44、t of cleaning the surface to be joined, this may be done by some acid cleaner. Soldering gives a satisfactory joint for light articles of steel, copper or brass, but the strength of soldering joint is rather less than a joint which is brazed, riveted or welded. These methods of metal are normally ad

45、opted for strong permanent joints.Pressure welding is known as the simplest method of welding two pieces of metal together. The ends of metal are heated to a while heatfor iron, the welding temperature should be about 1300in a flame. At this temperature the metal becomes plastics. The ends are then

46、presses or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation, and a film of oxide is formed on the heated surfaces.

47、For this reasons, a flux is applied to the heated metal. At welding heat, the flux melts, and the oxide Particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the center of the weld.Gas welding

48、 includes all the processes in which gases are used to obtain a hot flame. Those commonly used are acetylene, natural gas, and hydrogen in combination with oxygen. The maximum temperature developed by oxyhydrogen welding is 3600 (1980). Hydrogen is produced either by the electrolysis of water or by

49、passing steam over coke. An oxyacetylene weld is produced by heating with a flame obtained from the combustion of oxygen and with or without the use of a filler metal. In most cases the joint is heated to a state of fusion, and as a rule, no pressure is used.Are welding is a process in which coalesc

50、ence is obtained by heat produced from an electric arc. The electrode or filler metal is heated to a liquid state and deposited into the joint to make the weld. Contact is first made between the electrode and the work to create an electric circuit, and then, by separating the conductors, an arc is f

51、ormed. The electric energy is converted into intense heat in the arc, which attains a temperature around 10 000F (5500). Either direct or alternating current can be used for arc welding, direct current being preferred for most purposes. A d-c welder is simply a motor-generator set of constant-energy

52、 type, having the necessary characteristics to produce a stable arc. Arc welding uses commonly metal electrodes or carbon electrodes. Laser Welding is used because of lasers high heat intensity. It can be operated in any transparent medium without contact with the workpiece, since the laser delivers

53、 its energy in the form of light. In welding, the power is delivered in pulses rather than as a continuous beam, the beam is focused on the workpiece and the intense heat produces a fusion weld. Laser welding is slow and is used only for special jobs involving small weldments. Its greatest use is fo

54、und in the electronics industry.Explosion welding is a process that uses energy from the detonation of an explosive to join two pieces of metal. The explosion accelerates the pieces to a speed at which a metallic bond will form between them when they collide. The weld is produced in a fraction of a

55、second without the addition of filler metal. This is essentially a room temperature process in that gross heating of the workpieces does not occur. The faying surfaces, however, are heated to some extent by the energy of the collision, and welding is accomplished through plastic flow of the metal on

56、 those surfaces. Welding takes place progressively as the explosion and the forces it creates advance from one end of the joint to the other. Deformation of the weldment varies with the type of joint. There may be no noticeable deformation at all in some weldments, and there is no loss of metal.译文：铸

57、造、锻造和焊接1.铸造金属铸造是最古老的产业之一，远古时期和中世纪就有人使用和制造铸件了。5000年前人们只能用铜在开式模具中浇注简单的斧头，而公元前已经能够用分体式模具和型芯制造复杂的青铜雕塑了。中世纪末期，欧洲的教堂和家庭开使使用青铜和锡铅合金铸件制造器皿、进行装饰。 工程材料广泛使用铸铁得益于1709年希伯来用鼓风炼焦炉熔化金属，这为工业革命时期在建设中大量使用铸铁铺平了道路。 工业革命以后铸铁作坊纷纷兴起，生产的铸件主要用作建筑材料。19世纪铸件的产量虽然很大，但质量的提高并不普遍，工程中使用这些延展性很差的材料要冒极大的风险。 尽管铸件工人已经可以制造比较复杂的模型，但整个行业的情况

58、几乎没有什么变化，直到现代人们才逐渐了解那些影响铸件质量的各种因素。现代加工技术不再使用那些粗略的判断，而是对金属温度、材料特性以及生产过程中的其它因素进行客观的测量。这些改进不仅应用到铸铁，而且应用于各种浇注合金。 铸造方法基本有四种：砂型铸造、金属模铸造、熔模铸造和离心铸造。 砂型铸造是铸造厂最普遍使用的方法。铸造时，砂模装在没有上、下底的金属砂箱里。制模时砂箱用销子连在一起，这样取模时可以把砂箱拆开，并在浇注前作必要的校正。砂箱被夹在一起，为了防止浇注的金属在充满砂箱时把上砂箱和下砂箱顶开，有时也把上砂箱放在底部。分离式简单模具的制模过程可以用托架的铸造说明如下。 第一步先把托架模型放在

59、模板上，模型上覆盖面砂。面砂经过专门制造，质量很高，能够生成干净光滑的模腔印痕表面，抵抗熔融金属接触时的高温。面砂外面用型砂填充，型砂包括用过的面砂，经过仔细压紧，形成坚固的模腔，并具有良好的透气性，排放铸造时产生的气体。最后经过整型，平整砂模表面。 第二步把砂箱连同内部的模型就地倒置安放，在暴露的型砂上轻轻地覆盖一层分型砂，暴露的模型外覆盖面砂。（分型砂内没有粘结剂，这样在开箱取出模型时达到完全、清晰的分离。）第二个砂箱放在刚才第一个砂箱的上面，填满型砂。第二个砂箱填充时要插入两个或更多的塞子，以便塞子拔出时在砂子中间留下通孔。其中的一个塞子放置在模型的一侧。最后把砂子夯实、平整。 第三步是取模。把一根端部刻有螺纹的起模棒旋拧进模型，把模型周围的砂子弄湿，然后轻轻在各个方向晃动起模棒并仔细地取出模型。为了便于取模而不划伤模