机械设计制造及其自动化专业英语翻译

机械设计制造及其自动化专业英语翻译

Unit 1 Metals

金属

The use of metals has always been a key 在人类社会的发展中，金属的应用

factor in the development of the social systems 起着重点性的作用。构成物质的大概 100 种

of man. Of the roughly 100 basic elements of 基本元素中，大概有一半为金属。金属和非

which all matter is composed, about half are 金属之间的差别不是特别显然。最基本的定

classified as metals. The distinction between a 义集中在元素原子间存在的连结形式和与这

metal and a nonmetal is not always clear-cut. 些原子有关系的电子的某些特征。但是，在

The most basic definition centers around the 实质应用中，能够将拥有某些特征会合金属

type of bonding existing between the atoms of 定义为某种元素。

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 defined as an element which has a

particular package of properties.

Metals are crystalline when in the solid 除了少量例外金属在常温下是固态

state and, with few exceptions (e.g. mercury), 的。它们是热和电的良导体，不透光。它们

are solid at ambient temperatures. They are 常常拥有较高的密度。 很多金属拥有延展性，

good conductors of heat and electricity and are 也就是说，在不被损坏的状况下它们的形状

opaque to light. They usually have a 在外力的作用下能够发生变化。惹起永远变

comparatively high density. Many metals are 形所需的力和最后使金属断裂所需的力相当

ductile-that is, their shape can be changed 大，只管发生断裂所需的力远没有像所预期

permanently by the application of a force 的扯开金属原子所需的力那么大。

without breaking. The forces required to cause

this deformation and those required to break or

fracture a metal are comparatively high,

although, the fracture forces is not nearly as

high as would be expected from simple

consideration of the forces required to tear apart

the atoms of the metal.

One of the more significant of these 从我们的看法来看，在所有的特征中结

characteristics from our point of view is that of 晶性是最重要的。结晶体是这样一种构造，

crystallinity. A crystalline solid is one in which 构成它的原子定位在规则的三维摆列中，仿

the constituent atoms are located in a regular 佛位于三维棋盘的方格的角上。原子间距随

three-dimensional array as if they were located 着原子大小呈规律性变化，原子间距是金属

at the corners of the squares of a 的一种特征。三维摆列的轴线决定了晶体在

three-dimensional chessboard. The spacing of 空间中的方向。在工程实践中应用的金属由

the atoms in the array is of the same order as 大批的晶体构成，这些晶体称之为晶粒。在

the size of the atoms, the actual spacing being a 大多半状况下， 晶粒在空间中是自由摆列的。

characteristic of the particular metal. The 在原子范围内， 晶粒之间互相接触密切联合。

directions of the axes of the array define the 晶粒之间连结地区被称为晶界。

orientation of the crystal in space. The metals 机械设计制造及其自动化专业英语翻译

commonly used in engineering practice are

composed of a large number of such crystals,

called grains. In the most general case, the

crystals of the various grains are randomly

oriented in space. The grains are everywhere in

intimate contact with one another and joined

together on an atomic scale. The region at which

they join is known as a grain boundary.

An absolutely pure metal (i.e. one

composed of only one type of atom) has never

been produced. Engineers 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 metallic or nonmetallic.

These foreign elements may be detrimental,

they may be beneficial, or they may have no

influence at all on a particular property. If

disadvantageous, the foreign elements tend to

be known as impurities. If advantageous, they

tend to be known as alloying elements. Alloying

elements are commonly 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 it

can be said that the more deliberately an alloying

addition has been 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 controlled within

certain limits if consistent performance is to be

achieved in service. Thus chemical composition

has to be taken into account when developing an

understanding of the factors which determine the

properties of metals and their alloys.

Of the 50 or so metallic elements, only a

few are produced and used in large quantities in

绝对纯净的金属素来也没有被生产出来过。即便绝对纯净的金属能够生产出来，工程师们对它们也其实不会特别感兴趣，因为它们很柔嫩、柔弱。实质应用中的金属常常都包含着必定数目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利的或许它们对某种特定的属性没有影响。假如是有害的，这些外来元素被以为是杂质。假如是有利的，它们被以为是合金元素。在工程资猜中常常被特地地加入必定数目的合金元素。获取的物质被叫做合金。

金属和合金差别不大。金属这个词能够包含工业用纯金属和它的合金。或许能够这样说，合金元素越成心的被增添，被增添的合金元素的量越大，那么生产出来的产品越偏向于被称之为合金。不论如何，假如想使一种金属或合金在使用中表现出稳固一致的特征，在此中增添何种化学成分，它的量多多半应当在控制范围以内。所以，当想认识决定金属和合金性质的要素时，应充足考虑它们的化学构成。