求英语达人帮忙翻译一篇机械类英语文章，急！谢谢

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求英语达人帮忙翻译一篇机械类英语文章，急！谢谢(下半部分)~

Gears are often through-hardened by water or oil quenching in order to increase their resistance to wear.
齿轮通常都要经过在油介质或者水介质中的整体淬火，以达到增加耐磨性的目的。

If a low degree of hardness is satisfactory, through-hardening is probably the most desirable heat treatment process to be used because of its inexpensiveness.
如果对强度的要求较低，整体淬火可能是最适当的热处理方法，因为它的花费不高。

Case hardening is used for gear that require a hard surface and for which good accuracy is not necessary.
局部淬火使用在那些要求表面硬度较高的齿轮上，而且很难精确的达到。

The case hardening process results in gears that have much harder surfaces than cores.
局部淬火处理的齿轮具有比心部组织硬度高的表面硬度。

The advantage of case hardening is that, while the surface becomes hard and wear resistant, the toughness associated with the core remains.
局部淬火的优点是，表面具有高硬度和高耐磨性的同时，心部组织仍然保留着较高的韧性。

Carburizing, cyaniding, and induction hardening are some of the processes commonly used to produce the case hardening effect.
碳化、氰化、感应淬火是局部淬火中经常使用的处理方法。

If great accuracy is required, the gear must be ground.
如果对齿轮有精度要求，齿轮就必须经过磨削。

For problems in which corrosion resistant surfaces are desirable, nitriding is the process most often used. However, nitriding is a relatively expensive process and is used

only if other processes do not produce satisfactory results.
对于表面有抗腐蚀性要求的齿轮，渗氮是最常用的方法。然而，渗氮是一种相对较昂贵的热处理方法，并且通常只在其它热处理方法无法满足要求时才会使用。

Flame hardening and induction hardening are the methods usually used to harden larger gears.
火焰淬火和感应淬火是经常在大型齿轮上使用的热处理方法。

To sum up this discussion of specially heat treated steels, the designer should make use of carbon or alloy steels without special heat treatment if the relatively low surface

hardening of these untreated materials is satisfactory.
作为对特殊热处理钢材讨论的总结，设计师应当在未经热处理的低表面硬度材料能够满足使用要求时，使用不经过特殊热处理的碳钢或合金钢。

As the hardness requirement increase, the heat treated steels should be considered, with the least expensive steel that satisfies the strength and wear requirements being

chosen.
随着硬度要求的增加，应当考虑选择能够达到强度、耐磨性要求的最便宜的热处理钢材。

Nonferrous Metals Gears have been manufactured of nonmetallic materials for many years.
用非金属材料来制造齿轮已经有很长时间。

Rawhide, nylon, various type of plastics, and so on, have been used. The advantages obtained by using these materials are quiet operation, internal lubrication, dampening of

shock and vibration, and manufacturing economy.
生牛皮、尼龙、各种塑料、以及其它材料都得到应用。这些材料的优点有:静音操作、自润滑、减振性好、以及加工制造经济性好。

Their primary disadvantages are lower load carrying capacity and low heat conductivity, which results in heat distortion of the teeth and many result in a serious weakening of

the gear teeth.
它们的主要缺点是承载能力低和热传导性差，这些引起了轮齿的热变形和多种轮齿能力的降低。

Recently thermoplastic resins, with glass-fiber reinforcement and a lubricant as additives, have been used as gear materials.
最近，一种由玻璃纤维加固、并且带有自润滑剂的热塑性塑料，已经被用来做齿轮材料。

The composite material has resulted in greater load carrying capacity, a reduced thermal expansion, greater wear resistance and fatigue endurance.
合成材料具有更好的承载能力，更低的热膨胀系数，更好的耐磨性和更好的抗疲劳性能。

问题补充：Nonferrous Metals Nonmetallic Materials 麻烦翻译达人了！

补充这句是有点问题，Nonferrous Metals是有色金属。Nonmetallic Materials是非金属材料。用有色金属制非金属材料齿轮显然不对，我把那句翻成用非金属材料制非金属齿轮了。你对照下原文再。

问题补充：还漏了一段：Copper, zinc, aluminum, and titanium and titanium are materials used to obtain alloys that are useful gear materials.
铜、锌、铝和钛是经常使用在齿轮材料中的合金金属。

The copper alloys, known as bronzes, are perhaps the most widely used.
铜合金，比如青铜，可能是应用最广泛的合金。

They are useful in problems where corrosion resistance is important and also where large sliding velocities exist.
它们用在要求有较高耐腐蚀性的情况，以及有较大滑动速度存在时。

Because of their ability to reduce friction and wear, they are usually used as the material for making the worm wheel in a worm gear set.
因为具有减摩性和耐磨性的性能，它们通常用来制作涡轮减速器中的涡轮。

Aluminum and zinc alloys are used to manufacture gears by the diecasting process.
铝和锌的合金用来在模铸法中制造齿轮。

Friction and Lubrication
摩擦和润滑

In many of the problems thus far, the student has been asked to disregard or neglect friction.
到目前为止，在许多问题的处理中，学生都被告知不计入摩擦力或者忽略摩擦力。

Actually, friction is present to some degree whenever two parts are in contact and move on each other.
实际上，当两部分接触并且相对运动时，总要产生一定程度的摩擦。

The term friction refers to the resistance of two or more parts to movement.
边界摩擦力取决于两个或者多个部分相对运动时相互之间的阻碍程度。

Friction is harmful or valuable depending upon where it occurs.
根据产生时所处的位置不同，摩擦力可以是有害的也可以是有益的。

Friction is necessary for fastening devices such as screws and rivers which depend upon friction to hold the fastener and the parts together.
摩擦力在锁紧装置中是必须存在的，比如螺旋副和rivers，这些装置依靠摩擦力保持锁紧状态并且使各部分连接起来。

Belt drivers, brakes, and tires are additional applications where friction is necessary.
带传动、制动器、轮胎都是必需摩擦力的应用例子。

The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device.
机器中运动部件产生的摩擦力是有害的，因为它会降低装置的机械效率。

The heat produced by friction is lost energy because no work takes place.
摩擦产生的热量又损失了能量，因为它没有做功。

Also, greater power is required to overcome the increased friction.
另外，需要大量的能量来克服增长的摩擦力。

Heat is destructive in that it causes expansion.
热量引起的膨胀变形是具有破坏性的。

Expansion may cause a bearing or sliding surface to fit tighter.
热膨胀可能使轴承或者滑动表面更紧。

If a great enough pressure builds up because of expansion, the bearings may seize or freeze.
当热膨胀引起的压力变的足够大时，轴承可能停止运动甚至是烧结。

In addition, as heat is developed, bearings made from low temperature materials may melt.
另外，随着热量的增加，由低温工作用材料制成的轴承可能会熔化。

There are three types of friction which must be overcome in moving parts:
运动的物体中存在三种类型的必须克服的摩擦力：

(1)starting, (2)sliding, and(3)rolling.
1、静摩擦力，2、滑动摩擦力，3、滚动摩擦力

Starting friction is the friction between two solids that tend to resist movement.
静摩擦力是在两个相互限制对方运动的物体之间产生的摩擦力。

When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action.
当两部分在静止状态时，两表面的不规则形状使它们产生互相锁紧并且产生楔形作用。

To produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other.
在两部分产生运动的过程中，静止表面的楔形的尖端和凹处必然与另以表面相互滑进滑出。

The rougher the two surfaces, the greater is the starting friction resulting from their movement.
两表面越粗糙，由它们引起的静摩擦力就越大。

Since there is usually no fixed pattern between the peaks and valleys of two parts, the irregularities do not interlock once the parts are in motion but slide over each other.
由于通常两配合面的尖端和凹处没有固定的形状，一旦发生相对的运动不规则表面将不再互锁。

The friction of the two moving parts is known as sliding friction.
两运动表面间的摩擦被称作滑动摩擦。

As shown in Fingure1,starting friction is always greater than sliding friction.
如图1中所示，静摩擦力总是比滑动摩擦力大。

Rolling friction occurs when roller devices are subjected to tremendous stresses which cause the parts to change shape or deform.
滚动摩擦力产生在受到引起部件形变的巨大压力的滚动装置上。

Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill.
在这种情况下，滚动件的前部的材料产生堆积并且产生使物体向相反方向滚动的力。

This changing of shape, known as deformation, causes a movement of molecules.
这种被看作弹性变形的形状的改变，引起了分子之间的相对运动。

As a result, heat is produced from the added energy required to keep the parts turning and overcome friction.
结果，需要额外的能量来保持部件的转动并且克服摩擦力，并由此产生的热量。

The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces.
由不规则表面的楔形作用引起的摩擦力，能够部分的通过机器的表面精度被克服。

However, even these smooth surfaces may require the use of a substance between them to reduce the friction still more.
然而，即使这种光滑的表面也仍然需要在表面之间填充一些一些物质来降低摩擦。

This substance is usually a lubricant which provides a fine, thin oil film.
这种物质通常是能产生一层精细而且薄的油膜的润滑剂。

The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat.
这层薄膜保持两表面分离并且通过紧密的接触和产生的热量提供黏着力。

问题补充：Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts.
另一种降低摩擦的方式是使用不同的材料来制作轴承的表面和滚动部件。

This explains why bronze bearings, soft alloys, and copper and in oilite bearings are used with both soft and hardened steel shafts.
这便解释了为何青铜、软合金和紫铜用在与软表面或者硬表面钢轴配合的自润滑轴承中。

The oilite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing.
自润滑轴承是多孔状的。应此，当轴承浸入油中时，油会通过毛细作用充满轴承中的小孔。

This type of bearing carries its own lubricant to the points where the pressures are the greatest.
这种类型的轴承能把它自身存储的润滑油释放在压力最大的位置。

Moving parts are lubricated to reduce friction, wear, and heat.
对运动部件的润滑能够降低摩擦、磨损和生成的热量。

The most commonly used lubricants are oils, greases, and graphite compounds.
最常用的润滑剂是油、脂、以及石墨复合物。

Each lubricant serves a different purpose.
不同的润滑剂使用在不同的条件下。

The conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.
两运动表面的工作情况决定系统的润滑方式和布油方式。

On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other.
低速轻载运动的部件，一个润滑油槽通常就能够为相对运动表面提供足够的润滑。

Gear Materials (Reading Material)
齿轮材料（阅读材料）

Gears are manufactured from a wide variety of materials, both metallic as well as nonmetallic.
齿轮由多种种类的材料制造，包括金属材料和非金属材料。

As is the case with all materials used in design, the material chosen for a particular gear should be the cheapest available that will ensure satisfactory performance.
在设计中可以使用多种材料的情况下，对于特定齿轮，应当做到选用满足使用要求下的最便宜的材料。

Before a choice is made, the designer must decide which of several criteria is most important to the problem at hand.
在作出选择前，设计师必须决定在众多设计准则中哪个是当前最重要的。

If high strength is the prime consideration, a steel should usually be chosen rather than cast iron.
如果高强度是第一要考虑的因素，通常就选择钢材而不选择铸铁。

If wear resistance is the most important consideration, a can be made, for problems involving noise reduction, nonmetallic. Materials perform better than metallic ones.
如果耐磨性是最重要的因素，可以选用非金属材料要比金属材料更好，同时也可以解决降低噪声的问题。

However, as is true in most design problems, the final choice of a material is usually a compromise.
然而，在大部分实际设计问题中，对材料的最终决定往往是一个折衷的方案。

In other words, the material chosen will conform reasonably well to all the requirements mentioned previously, although it will not necessarily be the best in any one area.
换句话说，材料的选择要考虑到合理的达到所有的预定要求，尽管这样就不能在其中任何一方面达到最好。

To conclude this discussion we will consider the characteristics of various metallic and nonmetallic gear materials according to their general classifications.
为了总结这次讨论，我们将按照通常的分类来考虑多种金属和非金属齿轮材料所具有的特性。

Cast Irons
铸铁

Cast iron is one of the most commonly used gear materials.
铸铁是最常用的齿轮材料之一。

Its low cost, ease of casting, good machinability, high wear resistance, and good noise abatement property make it a logical choice.
它具有低成本，铸造性好，机械加工性能好，高耐磨性，以及高减噪性的特点，这些特点使铸铁成为一个合适的选择对象。

The primary disadvantage of cast iron as a gear material is its low tensile strength, which makes the gear tooth weak in bending and necessitates rather large teeth.
铸铁主要的缺点是，作为一种齿轮材料，铸铁的抗拉强度很低，这使得轮齿的抗弯强度很弱而且不能造出很大的轮齿。

Another type of cast iron is nodular iron, which is made of cast iron to which a material such as magnesium or cerium has been added.
另一种类型的铸铁是球墨铸铁，是在普通铸铁中加入了镁或者铈制成的。

The result of this alloying is a material having a much higher tensile strength while retaining the good wear and machining characteristics of ordinary cast iron.
这种合金的特点是既具有高的抗拉强度，又保持了普通铸铁的高耐磨性和优秀的机械加工性能。

Very often the combination of cast iron gear and a steel pinion will give a well balanced design with regard to cost, strength, and wear.
通常，铸铁大齿轮和钢制小齿轮的组合能够在成本、强度和耐磨性之间达到较好的平衡。

问题补充：Steel gear are usually made of pain carbon steels or alloy steels.
钢制齿轮通常由碳钢或者合金钢制造。

They have the advantage, over cast iron, of higher strength without undue increase in cost.
它们具有比铸铁更高的强度，同时又没有是成本过高的增加。

However, they usually require heat treatment to produce a surface hard enough to give satisfactory resistance to wear.
然而，它们通常需要经过热处理，以生成表面的硬化层来达到足够的耐磨性。

Unfortunately, the heat treatment process usually produces distortion of the gear, with the result that gear load is not uniformly distributed across the gear tooth face.
不幸的是，热处理过程通常会使齿轮发生扭曲和形变，这样齿轮上的载荷就不能均匀的分布到轮齿的表面。

Since alloy steels are subject to less distortion due to heat treatment than carbon steels, they are often chosen in preference to the carbon steels.
合金钢具有变形量小的特点，因此比碳钢更适合热处理，它们通常比碳钢使用的更多。

Although it is not the purpose here to discuss the various heat treatment methods and their effect on the properties of materials so treated, the designer should be aware of

possible problems arising from the use of heat treated materials.

尽管这里讨论的目的不是热处理的方法和这些方法在材料上产生的不同影响，设计师仍然应当认识到对不用热处理材料的选择可能带来的各种问题。

雅信翻译，里面有各个专业翻译，专业术语，而且意思大概都出不来了，比google和yahoo在线准确很多。到网上搜下雅信翻译，就能看到不少
我们毕设都用雅信，指导老师看了说差不多就行~~

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求英语达人帮忙翻译一篇机械类英语文章，急！谢谢

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