机械设计制造和自动化专业英语翻译

Unit 1 Metals

金属The use of metals has always bee n a key

factor in the development of the social systems

of man. Of the roughly 100 basic eleme nts 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 basic definition

centers around the type of bonding

existi ng betwee n the atoms of the

eleme nt, and around the

characteristics of certai n of the electrons

associated with these atoms.

In a more practical way, however, a

metal can be defined as an element which ________ has a_particular _____ package __ of

properties.

Metals are crystalline when in the

solid state and, with few excepti ons (e.g.

mercury), are solid at ambie nt

temperatures. They are good

con ductors of heat and electricity and are

opaque to light. They usually have a

comparatively high den sity. Many metals are ductile -that is, their shape can be

changed permanently by the

applicati on of a force without break ing.

在人类社会的发展中，金属的应用 起着关键性的作用。构成物质的大约 100种

基本元素中，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。最基本的定 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 往往具有较高的密度。 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。The forces required to cause this

deformati on and those required to

break or fracture a metal are

comparatively high, although, the

fracture forces is not n early as high as

would be expected from simple

con siderati on of the forces required to

tear apart the atoms of the metal.

One of the more sig ni fica nt of these

characteristics from our point of view is

that of crystall in ity. A crystalli ne solid is one in

which the constituent atoms are located in a

regular

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则的三维排列中，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。three-dime nsional array as if they were

绝对纯净的金属从来也没有被生产出来 过。即使绝对纯净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。在工程材料中往往被特意地加入一定 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，合金元素越故意的被添加，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 located at the corners of the squares of

a three-dimensional chessboard. The

spaci ng of the atoms in the array is of the same

order as the size of the atoms, the actual spaci ng being a

characteristic of the particular metal.

The directi ons of the axes of the array define the

orientation of the crystal in space. The metals

commonly used in engin eeri ng practice are

composed of a large number of such crystals,

called

grains. In the most general case, the

crystals of the various grains are

ran domly orie nted in space. The gra ins are

everywhere in in timate con tact with one ano ther

and joined together on an atomic scale. The regi

on at which they join is known as a grain boun

dary.

An absolutely pure metal (i.e. one composed

of only one type of atom) has n ever bee n

produced. Engin eers would not be particularly in

terested in such a metal even if it were to be

produced, because it would be soft and weak. The

metals used commercially in evitably

contain small amounts of one or more foreig n

eleme nts, either metallic or

nonm etallic. These foreig n eleme nts

may be detrime ntal , they may be

ben eficial, or they may have no

in flue nee at all on a particular property. If disadva ntageous, the foreig n

eleme nts tend to be known as

impurities . If advantageous, they tend

to be known as alloying elements .

Allo ying eleme nts are com monly added

deliberately in substantial amounts in

engin eeri ng materials. The result is

known as an alloy.

The dist inction betwee n the

descriptors “ metal ” and “ alloy ” is

not clear-cut. The term “ metal ” may

be used to en compass both a commercially pure metal and its alloys.

Perhaps it can be said that the more 止最重要的是铁，以它为基础构成了处处可 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 抗磨损和耐咼温的用途，由于钛合金具有咼 强度和低密度的综合特性，钛被广泛应用于 航空工业中。镍合钛有咼成本和咼质量的使 用特性，事实上，它们高的成本限制了它们 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 焊接等特殊工艺来加工出来；它可以被循环 利用；它的成本和实用性是首要的。 deliberately an allo ying additi on has

bee n made and the larger the amount of the