专业英语

It is known that metals are very important in our life. Metals have the greatest importance for industry. All machines and other engineering[] constructions have metal[] parts; some of them consist only of metal parts.

There are two large groups of metals:

1) Simple metal- more or less pure chemical elements[]

2) Alloys[]- materials consisting of a simple metal combined with some other elements.

About two thirds of all elements found in the earth are metals, but not all metals may be used in industry. Those metals which are used in industry are called engineering metals. The most important engineering metal is iron[], which in the form of alloys with carbon[] and other elements, finds greater use than any other metal. Metals consisting of iron combined with some other elements are known as ferrous[] metals; all the other metals are called nonferrous[] metals. The most important nonferrous metal are copper[], aluminum[], lead[], zinc[], tin[], but all these metals are used much less than ferrous metals, because the ferrous metals are much cheaper.

Engineering metals are used in industry in the form of alloys because the properties[] of alloys are much better than the properties of pure[] metals. Only aluminum may be largely used in the form of simple metal. Metals have such a great importance because of their useful properties or their strength, hardness, and their plasticity[].

Different metals are produced in different ways, but almost all the metal are found in the forms of metal ore[] (iron ore, copper ore, etc[et cetra].)

The ore is a mineral[] consistence of a metal combined with some impurities[]. In order to produce a metal from some metal ore, we must separate these impurities from the metal that is done by metallurgy['mɛtə,lɝdʒɪ].

engineering[] 工程 metal[] 金属

elements[] 元素 alloys[] 合金 iron[] 铁

carbon[] 碳 copper[] 铜

aluminum[] 铝

nonferrous[] 非铁金属，有色金属 ferrous[] 黑色金属 lead[] 铅 zinc[] 锌 tin[] 锡

properties[] 性能 pure[] 纯的

plasticity[] 可塑性 ore[] 矿石

mineral[] 矿物

impurity[] 不纯的 metallurgy ['mɛtə,lɝdʒɪ] 冶金术

2. Plastics and Other Materials

Plastics[] have specific properties which may make them preferable[] to traditional materials[] for certain uses. In comparison[] with metals, for example, plastics have both advantages and disadvantages. Metals tend to be corroded[] by inorganic[] acids[], such as sulphuric[] acid and hydrochloric[] acid. Plastics tend to be resistant to these acids, but can have dissolved or deformed by solvent[], such as carbon tetrachloride[], which have the same carbon base as the plastics. Color must be applied to the surface of metals, whereas it can be mixed in with plastics. Metals are more rigid[] than most plastics while plastics are very light, with a specific[] gravity normally between 0.9 and 1.8. Most plastics do not readily[] conduct[] heat or electricity[]. Plastics soften slowly and can easily be shaped[] when they are soft.

塑料具有特殊的性能。对于某种用途而言，这些性能使得塑料比传统材料更为可取。例如，跟金属相比较，塑料既有优点也有缺点。金属易受到无机酸的腐蚀，如硫酸和盐酸，塑料能抵抗这些酸的腐蚀，但可被溶剂所溶解或引起变形，例如溶剂四氯化碳与塑料具有同样的碳基。颜色必定只能涂到金属的表面。而它可以跟塑料混合为一体。金属比大多数塑料刚性要好，而塑料则非常之轻，通常塑料密度在0. 9-1. 8之间。大多数塑料不易传热导电。塑料能缓慢软化，而当其还是在软的状态时，能容易成形。

It is their plasticity[] at certain temperatures[] which gives plastics their main advantages over many other materials. It permits the large-scale production of molded[] articles, such as containers, at an economic unit cost, where other materials require laborious[] and often costly processes involving cutting, shaping, machining, assembly[] and decoration.

在某一温度下塑料是处于塑性状态的，这就使塑料具备超过许多其他材料的主要优点。它容许大量生产单位成本低廉的模制式器件，例如，各种容器。于此，若用其他材料则需要大量劳力和往往需要很费钱的加工工艺，比如，切割、成形、加工、装配和装饰。

Plastics not only replace other materials. Their properties can be exploited[] for entirely[] new applications. For example, plastics heart valves[] 心脏瓣膜 （阀） and other human 'spare parts' have make possible many recent developments in surgery[].

There is no single plastics material which is suitable for all applications. It is important that the most suitable plastics should be chosen, and if necessary adapted[], for each particular requirement. It is also important that the properties of the plastics chosen should be exploited to the best advantage.

A plastics article may need to differ in design and appearance from a similar article made from another material such as metal or wood. This is due not only to the properties of plastics but

also to the techniques[] employed in fabricating[] plastics. These techniques include injection[] molding[], blow molding, compression molding, extrusion[] and vacuum[] forming.

3. Casting and Die-Casting Alloys

Casting[] is one of the oldest metal working techniques known to man. Our country made metal castings as early as 2000 B.C., and the process used then is not much different in principle[] from the one used today.

铸造是入类所掌握的最古老的金属加工技术之一。我国早在公元前2000年就已把金属制成铸件，而所使用的工艺从原理上和今天的工艺没有多大的区别。

Foundry[] processes consist of making molds, preparing and melting[] the metal, pouring[] the metal into the molds, and cleaning the castings. The product of the foundry is a casting, which may vary from a fraction[] of a kilogram to several hundred tons. It may also vary in composition[] as practically all metals and alloys can be cast.

铸造工艺由制模、备料和金属熔炼，金属液浇注入模和铸件清砂等。铸造的产品是铸件，铸件可能从零点几公斤到几百吨范围变化。实际上所有金属在成分上也是变化的，而合金也可以铸造。

The metals most frequently cast are iron, steel, aluminum and so on. Of these, iron, because of its low melting point, low price and ease of control, is outstanding for its suitability[] for casting and is used far more than all the others.

最常铸造的金属是铸铁、钢、铝等等。这些金属中，铸铁，由于其低熔点，低价格和易控制，因而其铸造适应性是最突出的，而且使用也远比所有其他金属多。

Casting is a widely used method of producing metal products, particularly those which are intricate[]. Since molten materials will readily take the shape of the container into which they are poured, it is nearly as easy to cast fairly complex shapes as to produce simple forms.

由于熔融的物料能容易取得被浇注进去的容器〔模型)的形状，因此，几乎像生产简单形状铸件那样颇为容易地铸造出复杂形状的铸件。

The place where the metals are cast is called a foundry. The most important of cast metals is cast iron which is made from pig iron by remelting it in a special melting furnace[] called a cupola[].

铸造金属的地方叫做铸造车间。最重要的铸造金属是铸铁，铸铁是用生铁在一个特殊的熔炉—叫冲天炉的炉子中重新熔炼而制造出来的。

From the cupola, the cast iron flows into ladles[] of different size, and from these ladles it is poured into the molds.

从冲天炉中出来的铁水流入到不同规格的铁水包中，并从这些铁水包中被浇注到模型中。 The molds may be of two kinds: sand molds and metal molds. A metal mold consists of two hollow parts which should be joined for pouring the metal into it. The inside of this mold is covered with carbon or graphite[] so that the metal could not stick[] to the wall of the form. When the metal has solidified[], these hollow parts are disjoined and the casting is taken out. There are also special molds in which large blocks of steel

can be cast. These molds are usually made of cast iron and are called ingot[] molds, which the blocks of steel produced by pouring the metal into these molds are called ingots and the process is called ingot casting.

模型有两种类型:砂模和金属模。金属模是由两个中空的部件组成，它们应被联结在一起以便将金属液浇入模箱中。这模腔的内侧是要涂以碳粉或石墨，因此金属不玫于粘贴到型腔壁上口当金属液凝固后，这中空的型箱部件被打开并取出铸件。也有一种特殊模型，在该模型中可以铸造大型钢块。这些模型通常用铸铁米制造，并被称为锭模。而浇注金属液到这些模子中生产出的钢块被称为钢锭。该工艺过程叫锭铸。

A relatively[] wide range of nonferrous alloys can be die-cast. The principal base metals used, in order to commercial importance, are zinc, aluminum, copper, magnesium[], lead, and tin. The alloys may be further classified as low-temperature alloys and high-temperature alloys; those having a casting temperature below 538C, such as zinc, tin, and lead, are in the low-temperature class. The low-temperature alloys have the advantages of lower cost of production and lower die-maintenance[] costs. As the casting temperature increases, alloy and other special steels in the best treated condition are required to resist the erosion[] and heat checking[] of die surface. The destructive[] effect of high temperatures on the dies has been the principal factor in retarding[] the development of high-temperature die castings.

相当大量的有色金属合金可以进行模铸}h用的主要而基本的金属，按其在工业上应用的重要性的顺序是锌、铝、铜、锰、铅和锡。这些合金可以进一步进行分类为低温类合金和高温类合金。铸造温度低于538℃的那些合金，就像锌、锡和铅,是属于低温类合金。低温类合金具有低生产成本和低的模具维修费用等优点。当铸造温度上升时，需要最佳条件下处理过的合金钢和其他特种钢来抵抗腐蚀及防止模具表面的热裂纹。高温在模具上的损坏作用已经成为阻碍、延缓高温模铸发展的主要因素。

Another factor governing[] the choice of alloy is the erosive[] or solvent[] action of the molten metal on the respective[] machine parts and dies. This action increases with temperature, although it is more pronounced[] with some alloys than with others. Aluminum, in particular, has a destructive action on ferrous metals and, for this reason, is seldom melted in the machine, whereas the copper-base alloys are never melted in the machine.

控制选择合金的另外一个因素就是熔融的金属在相关的机器零件上和模具上的腐蚀或溶解作用。 这种作用随着温度的升高而增加，甚至某些合金比另一些合金更为明显。特别是.铝对黑色金属有一种破坏作用，为此、铝几乎不熔混于机器零件中，而铜基合金是决不能熔混于机器构件中的。

4. Forging

Press forging[] employs a slow squeezing[] action in deforming[] the plastic metal, as contrasted with the rapid-impact[] blows of a hammer. 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 commonly used, range in capacity[] from 500 to 1000 tons.

与锤锻的快速冲击不同，压力机锻造是用缓慢的挤压作用使塑性金属变形。这挤压作用完全被施加到正在被压锻的零件中心位置上，直至彻底使整个工件得到加工。这些压力机都是立式的，可能是机械操作也可能是液压操作的。机械操作压力机，操作速度比较快，使用最普遍，锻造能力从5400吨到10000吨范围。

For small press forgings, closed impression dies are used and only one stoke of the ram[] is normally required to perform[] the forging operation. The maximum[] pressure is built up at the end of the stroke which forces the metal into shape. Dies may be mounted[] as separate units, or all the cavities may be put into single block. For small forgings, individual[] die unites are more convenient. There is some difference in the design of dies for different metals; copper-alloy forgings can be made with less draft[] than steel, consequently more complicated[] shapes can be produced. These alloys flow well in the die and are rapidly extruded

对于小型压力锻使用闭式锻模。通常要求锻锤仅一个冲程就完成锻造工艺。在冲程终端产生最大压力，该冲击压力迫使金属成形。模具可由各白的单元装配而成，即把所有个别模腔都放到一起，组成整体。对于小型锻件使用分模装置更为方便。对于不同的金属在模具设计上有些区别.铜合金锻件比钢件用较小的拔模斜度，因此可生产更加复杂形状的锻件。这些合金在该种模具中流动性好，而且能快速挤压成形。

In the forging press, a greater proportion of the total work put into the machine is transmitted[] to the metal than in a drop hammer press. Much of the impact of the drop hammer is absorbed by the machine and foundation. Press reduction of the metal is faster, and the cost of operation is consequently lower. Most press forgings are symmetrical[] in shape, having surfaces which are quite smooth, and provide a closer tolerance[] than is obtained by a drop hammer. However, many parts of irregular[] and complicated shapes can be forged more economically by drop forging. Forging press is often used for sizing operations on parts made by other forging processes.

锻压机比落锤锻，输入到机器里的总能量中有更大部分的能量被传输到金属坯料上。落锤锻的冲击能量被机器和基础吸收得较多(比起压力机来〕。金属上的压力衰减较快，因此生产成本比较低。大多数压力锻锻件形状、产生的表面都是对称的，而且表面非常光滑，并比落锤锻件的公差尺寸更加精确。然而落锤锻造可以锻制形状复杂而不规则的锻件，因而较为经济。锻压机常常用来为其他锻造工艺所生产的锻件进行整形和校正加工用。

In drop forging, a piece of metal, roughly[] or approximately of the desired[] shape, is placed between die faces having the exact form of the finished piece, and forced to take thin form by drawing the dies together. Large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press 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 too hot, for overheated steel will have poor mechanical properties when cooled. In heating for forging, temperature is usually judges by the eye, but where large numbers of the same pattern are made, the piece to be forged are heated in furnaces[] in which the temperature is indicated[] by pyrometers[], and often is automatically controlled.

在落锤锻中，一块金属坯料，粗糙的即大体像所要求零件形状那样，被放入到具有成品件那样精确形状的模面之间，然后施加压力使模具紧紧结合在一起以锻取模腔形状。这一方法广泛用来制造钢件和黄钢件。大型金属锭现在几乎都是用液压压力机来锻造的，而不用蒸汽锤。因为用压力机锻造，变形更加深透。将来压力机可对付冷金属锭并能加工得到更加精确的尺寸。锻造将在大约与辊轧同样的温度下进行，这种工艺正像轧制那样可改善金属的物理性能。最后火锻时，不使钢太热很重要，因为过热钢冷却后，其机械性能较差。为锻件加热，温度通常是以肉眼来判断的，但在生产大量相同锻件的场合，要锻造的坯件是在有高温计指示温度的炉子中来加热，并且常常是自动控制的。

5. Soldering and Welding

There are a number of methods of joining metal articles[] together, depending on the type of metal and the strength of the joint which is required.

把金属件连接在一起的方法有若干个，用哪一种方法，要根据金属种类和所要求的焊缝强度来决定。

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 most important operations in soldering is that of cleaning the surface to be joint, this may be done by some acid cleaner.

软焊是要用溶融状态的第三种金属来使两件金属连接在一起的工艺。焊料由锡和铅组成。而常常含有铋和镉。目的是要降低熔点。软钎焊中最重要的工序之一就是清理焊缝表面。这可以用某种酸性清除剂来进行。

Soldering gives a satisfactory joint for light articles of steel, copper or brass[], but the strength of a soldered joint is rather less than a joint which is brazed[], riveted[] or welded[]. These methods of joining metal are normally adopted[] for strong permanent[] joints.

软钎焊能为轻型钢件、铜件和黄铜件生产满意的焊缝，但软钎焊的焊缝强度比起硬钎焊、铆接和焊接来要弱些。连接金属的这些方法，通常用来产生强固的永久性的焊缝。

The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heat-for iron, the welding temperature should about 1300C-in a flame[]. At this temperature the metal becomes plastic. The ends are then pressed 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. For this reason, 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. A number of different types of weld may be used, but for fairly thick bars of metal, a v-shaped weld should normally be employed[]. It is rather stronger than the ordinary but weld.

把两件金属焊在一起的最简单的方法称做压力焊。用火焰把金属两端加热到白炽状态—铁的焊接温度为1300C左右—在这一温度下，金属变成塑性，然后对两端施压或锤击使之结合在一起。最后再将焊缝清理千净。必须注意首先保证表面完全清洁，因脏物将会使焊缝强度削弱。此外，加热铸铁或钢到高温会引起氧化井在焊接表面形成氧化皮。因此用助焊剂

施于加热的金属上。达到焊接温度时刻，助焊剂熔化，将氧化物粒子跟任何其他可能存在的杂质一起都熔解于助焊剂中，金属表面被压合在一起，而助焊剂就从焊缝中间被挤出。可能使用若干不同类型的焊缝，但对于颇为粗厚的金属件，通常使用V型焊缝。该焊缝比起普通的对接焊缝来要强固些。

The heat for fusion[] welding is generated in several ways, depending on the sort of metal which is being welded and on its shape. An extremely hot flame can be produced from an oxy-acetylene[] torch[]. For certain welds an electric arc is used. In this method, an electric current is passed across two electrodes[], and the metal surfaces are placed between them. The electrodes are sometimes made of carbon, but more frequently they are metallic[]. The work itself constitutes one of them and the other is an insulated[] filler[] rod[]. An arc struck[] between the two, and the heat which is generated melts the metal at the weld. A different method is usually employed for welding sheets or plates of metal together. This is known as spot welding. Two sheets or plates are placed together with a slight[] overlap[], and a current is passed between the electrodes. At welding temperature, a strong pressure is applied to the metal sheets. The oxide film, and any impurities which are trapped[] between the sheets, are squeezed out, and the weld is made.

可用几种方法来产生溶焊的热，用何种方法，要根据将要焊接的金属种类和根据其形状来决定。由氧乙炔焰可产生强烈的火焰。对于某种焊缝，可用电弧来焊接。在这一系列重要的焊接过程中，电弧可为熔化金属供热，而焊剂起着保护和清理焊缝的作用，而且常常也是起着熔炼控制作用。最广泛使用的助焊剂保护电弧焊的形式是一种称作金属弧焊的手工操作工艺。在这一方法中，电流经两个电极流过，而金属表面则被置于两电极之间。电极(电焊条)有时用碳棒制作，但更常用金属来制作。工件本身构成它们中的一极而另一极是一具有绝缘填充剂的焊条。两极之间电弧放电，由此产生的热去熔化在焊缝处的金属。通常使用不同的方法去把金属薄板或厚板焊接在一起。这就叫做点焊。两块薄板或厚板以边沿稍稍搭叠的方式放在一起，一电流从两极之间通过.达到焊接温度时刻，对金属板施加强压，氧化皮和陷入薄板中间任何杂质都会被挤出，而完成了焊缝连接.

6. Heat Treatment and Hot Working of Metals

We can alter[] the characteristics[] of steel in various ways. In the first place, steel which contains very little carbon will be milder than steel which contains a higher percentage of carbon, up to the limit of about 1.5%. Secondly, we can heat the steel above a certain critical[] temperature, and then allow it to cool at different rates. At this critical temperature, changes begin to take place in the molecular[] structure of the metal. In the process known as annealing[], we heat the steel above the critical temperature and permit it to cool very slowly. This causes the metal to become softer than before, and much easier to machine. Annealing has a second advantage; it helps to relieve[] any internal stresses which exist in the metal. These stresses are liable[] to occur through hammering or working the metal, or thorough[] rapid cooling. Metal which we cause to cool rapidly contracts[] more rapidly on the outside than on the inside. This produces unequal contractions, which may give rise to distortion[] or cracking[]. Metal which cools slowly is less liable to have these internal stresses

than metal which cools quickly.

On the other hand, we can make steel harder by rapid cooling. We heat it up beyond the critical temperature, and then quench[] it in water or some other liquid. The rapid temperature drop fixes the structure change in the steel which occurred at the critical temperature, and makes it very hard. But a bar of this hardened steel is more liable to fracture[] than normal steel. We therefore[] heat it again to a temperature below the critical temperature, and cool it slowly. This treatment is called tempering[]. It helps to relieve the internal stresses, and makes the steel less brittle[] than before. The properties of tempered steel enable us to use it in the manufacture of tools which need fairly hard steel. High carbon steel is harder than tempered steel, but it is more difficult to work.

These heat treatments take place during the various shaping operations. We can obtain bars and sheets of steel by rolling the metal through huge rolls in a rolling mill[]. The roll pressures must be much greater for cold rolling than for hot rolling, but cold rolling enables the operators to produce rolls of great accuracy[] and uniformity[], and with a better surface finish. Other shaping operations include drawing into wire, casting in moulds, and forging.

The mechanical working of metal is the shaping of metal in either a cold or hot state by some mechanical means. This does not include the shaping of metals by machine or grinding, in which processes metal is actually machined off, not does it include the casting of molten metal into some form by use of molds. In mechanical working processes, the metal is shaped by pressure-actually forging, bending[], squeezing, drawing, or shearing[] it to its final shape. In these processes the metal may be either cold-or hot- worked. Although normal room temperatures are ordinarily used for cold working of steel, temperatures up to the recrystallization[] range are sometimes used. Hot working of metals takes place above the recrystallization or work-hardening range. For steel, recrystallization starts around 650 to 700C, although most hot work on steel is done at temperature considerably[] above this range. There is no tendency[] for hardening by mechanical work until the lower limit of the recrystalline range is reached. Some metals, such as lead and tin, have a low recrystalline range and can be hot-worked at room temperature, but most commercial metal require some heating. Alloy composition[] has a great influence[] upon the proper[] working range, the usual result being to raise the recrystalling range temperature. This range may also be increased by prior cold working.

7. Kinds of Steels, Mechanical Properties of Metals

There are two general[] kinds of steel: carbon steel and alloy steel. Carbon steel contains only iron and carbon, while alloy steel contains some other alloying elements such as nickel[], chromium[], manganese[], molybdenum[], tungsten[], vanadium[], etc.

1. Carbon steels

(1) Low carbon steel containing from 0.05 to 0.15 percent carbon; this steel is also known as machine steel.

(2) Medium carbon steel containing from 0.15 to 0.60 percent carbon.

(3) High carbon steel containing from 0.6 to 1.50 percent carbon: this steel is sometimes called \"tool steel\".

2. Alloy steels

(1) Special alloy steel, such as nickel steel, chromium steel. (2) High-speed steel also known as self-hardening steel.

Carbon steels are the most common steels used in industry. The properties of these steels depend on the percentage of carbon they contain. Low-carbon steels are very soft and can be used for bolts[] and for machine parts that do not need strength.

Medium carbon steel is a better grade and stronger than low carbon steel. It is also more difficult to cut than low carbon steel.

High carbon steel may be hardened by heating it to a certain temperature and then quickly cooling in water. The more carbon the steel contains and the quicker the cooling is, the harder it becomes. Because of its high strength and hardness, this grade of steel may be used for tools and working parts of machines.

But for some special uses, for example, for gears[], bearings[], springs[], shafts[] and wire[], carbon steels cannot be always used because they have no-properties needed for these parts.

Mechanical properties are the characteristic responses[] of a material to applied forces. The knowledge of mechanical properties of materials is very essential[] in order to construct a mechanically sound[] structure such as a bridge on the river. Mechanical properties can be determined[] by conducting experimental tests on the material specimen[]. Some important mechanical properties of materials are:

(1) Strength (in tension[], compression, shear and bending) (2) Stiffness[]

(3) Ductility[] (4) Impact strength (5) Hardness

(6) Toughness[]

1. Strength or mechanical strength of a material may be defined as the ability of the material to sustain loads without undue[] distortion[] or failure. Material should have adequate[] strength when subjected[] to tension, compression, shear, bending or torsion[] as per the intended use. For example the crankshaft[] of an automobile[] should have proper torsion strength.

2. Stiffness. Stiffness is the ability of a material or shape to resist elastic[] deflection[]. For identical[] shapes, the stiffness is proportional[] to the modulus[] of elasticity[]. A material which deforms less under a given load is more stiff than on which deforms more.