广工材加专业英语复习总结题.docx

1、广工材加专业英语复习总结题 热处理锻后进行一次或多次重新加热和冷却操作的热循环过程，以便使锻件获得所需的显微组织和机械性能。 几乎没有一类锻件是生产出来而不经过热处理的。未经过热处理的锻件经常被作为低碳钢而应用在非关键的场合或者是为接下来的进一步的热机械加工和热处理做准备。钢铁的化学成分、产品的尺寸和形状以及期望得到的属性都是决定产品生产周期的重要因素The object of heat treatment metals is to impart certain desired physical properties to the metal or to eliminate undesirab

2、le structural conditions which may occur in the processing or fabrication of the material ,In the application of any heat treatment it is desirable that the “previous history” or structural condition of the material be known so that a method of treatment can be prescribed to produce the desired resu

3、lt. In the absence of information as to the previous processing, microscopic study of the structure is desirable to determine the correct procedure to be followed金属材料热处理的目的是为了使材料获得某些期望得到的物理性能或者是消除发生在金属成型或者加工过程中所产生的不期望得到的组织状态。在一些热处理应用中，为制定得到材料所需要性能的一种热处理方法时，了解材料在热处理前的加工史和结构状态是必须的。热处理前期，在缺乏材料相关信息的情况下，

4、为了确定下一步的热处理工序，对材料结构的微观研究是必须的。There is no generally accepted definition of a plastic, but it can be regarded as a material containing a synthetic high polymer as the major constituentPolymers are materials of high molecular weight formed by joining together many(poly) small moleculesIn some plastics

5、the polymer may be the only constituent，but more usually a variety of other substances are incorporated such as fillers，pigments.antioxidants, plasticizers, etcThese additives will enhance specific properties andor facilitate processingAlmost all commercial plastics at present are based upon organic

6、 polymers.The word plastics is closely associated in many minds with cheap,brightly coloured products of limited life. The time has probably come to adapt a new name more worthy of the exciting range of polymer materials with many different properties which are available to engineers.塑料没有被普遍认可的定义，但认

7、为它是一种以合成高聚物作为主要成分的材料。高聚物是一种高分子量材料，通过连接许多小分子而成。有些塑料，多聚物是唯一组成成分，但更多塑料中通常要加入多种其它物质，比如填充剂、着色剂（颜料）、抗氧剂、增塑剂等。这些添加剂将改善一些特殊性能或有助于成型。目前几乎所有商业塑料都是以有机高聚物为基体的。在很多人的脑海里，塑料一词是与那些廉价、色彩明亮、“寿命”有限的产品联系在一起的。目前塑料定义已可能迎来新的术语，以阐述具有不同属性可用于工程领域的各种聚合物材料From the production point of view the main advantage of plastic material

8、s is their relatively low melting point and their ability to flow into a mouldGenerally there is only one production operation required to convert the chemically manufactured plastic into a finished article.Contrast this with metal where generally many operations are required to convert the raw mate

9、rial into its final shape 从生产的角度来说，塑料的主要优势在于其低熔点和良好的流动性。一般来说，化工氧化塑料转变成成品只需要通过一道加工工序。与金属材料相比，金属材料需要经过多道工序才能将原材料转变成成品。It is convenient to divide plastics into two groups depending upon the geometrical form of the polymer moleculeThe first group are the linear polymers which are the basis of thermoplas

10、tics;the second group the network polymers which are the basis of thermosetting plastics.根据聚合物分子的几何形态可以很方便地将塑料分为两类。第一种是直链多聚物，以热塑性塑料为主。第二类为网状多聚物，以热固性塑料为主。These polymers set after being melted to a liquid state by heating; hence the term thermosetting plastic. This process of solidifying is known as c

11、uring. During curing all the small molecules are chemically linked together to form one giant network molecule. Hence they are distinguished from the linear polymer (thermoplastics)by being called network polymers这些聚合物通过加热被熔化为液态后再变为固态，因此采用术语热固性塑料。凝固的过程称为固化。固化时所有小分子通过化学反应连接起来形成巨大的网状分子。因此它们区别于线状聚合物（热塑

12、性塑料） 而正如其名网状聚合物。The change from the liquid state to solid is irreversible, and further heating results only in chemical breakdown; not melting. All the common thermosetting plastics are synthetic resins like epoxide, melamine, phenol, polyester for example, which in the hard state are invariably gla

13、ssy and brittle in nature. Their structure is based upon carbon like the linear polymers. The silicones, however, are another family of materials whose structure is based upon silicon, not carbon. They are usually grouped with the common thermosetting plastics, the properties of some of which the co

14、mmonly used either to improve or modify the mechanical or chemical properties of the resin, or in order to give cheaper material. 从液态到固态的转变是不可逆的，进一步加热只能导致化学分解，而非熔化。所有的常见热固性塑料都是合成树脂，比如象环氧化物、三聚氰胺、酚、聚酯，硬态时它们性质类似玻璃、易碎。象直链多聚物它们的结构以碳为基础。然而，硅树脂却是基于硅而非碳的另一类物质。它们和常见的热固性塑料归于一类。图11.8表给出了部分材料的属性。请注意：常采用填充材料去提高或

15、改善树脂的力学性能或化学属性，或为了得到更廉价的材料This is the traditional moulding method which has been used in the plastics industry for many years. The process is superficially similar to the hot pressing of metals in so far that the plastic is placed into a heated mould on a vertical press and subjected to pressure. Th

16、e main difference is that a thermosetting plastic is moulded at melting temperature where as a metal is hot pressed at sintering temperature. The plastic is held in the mould from the liquid state until the curing stage is over when polymerization is complete. It should be noticed that compression m

17、oulding would be impracticable for thermoplastics which have no curing stage during which a chemical reaction take place; because the mould would require cooling each cycle in order to allow the component to harden sufficiently for extraction.压缩成型是传统的成型方法，已在塑料工业中使用多年。这个工艺表面上类似金属热压工艺。塑料在立式大力机上的模具中加热，

18、承受压力。其主要的区别是，热固性塑料是在熔化温度上成型的，而金属是在烧结温度上热压。这种塑料是在模具中从液态到固化阶段结束，即聚合完成。需要指出的是，热塑性塑料压缩成型是不可行的。因热塑性塑料没有发生化学反应的固化阶段，为使塑料足够硬化以便脱模，模具每个工作循环都需要冷却。The process cycle time obviously depends upon the curing time, and with modern plastic this has been considerably shortened. Vertical hydraulic presses are usually

19、 used up to 0.5 MN capacity having an upstroke or downstroke action. Pressure applied to the plastic in the mould is to the order of 15N/mm2, and the cooling temperature is to the order of 200C. Mould heating can be successfully accomplished using steam, gas or electric resistance heating成型加工周期明显取决于

20、固化时间，而且使用现代塑料，周期会大大缩短。立式液压机通常采用上下行程为高达0.5MN容量。在模具成型的的塑料应用压力要有15N/mm2，以及固化温度至200。通过使用蒸汽，燃气或电阻加热可顺利完成模具加热。Moulds, which may be single or multi-cavity, usually consist of a female and male die giving the component its exterior and interior shape .The first compression moulds were filled with plastic po

21、wer by hand ,and allowance had to be made for inaccurately measured excess plastic to leak out of the mould in the form of flash .Hence ,an open flash mould of the type shown in Fig 11.9 must be used in such a case.Lowance must be made in the mould size for shrinkage because the ratio (volume of pow

22、ervolume of moulding) can vary between 31and 101模具可能是单一或多重型腔组成，通常由凸凹模来确定其外观和内部形状。压缩模具用塑料粉末充满，和必须留有预留量，以不准确地测量过剩塑料，泄漏塑料形成了制品飞边。因此， 11.9所示的溢式压缩模类型必须在这种情况下使用。由于收缩率，模具的尺寸必须留有预留量，因为（粉末体积/体积成型）的比值可以从3 / 1到10 / 1变化。Compression moulding is now more often carried out using closed moulds which give no trouble

23、some flash upon the component. They require an accurate amount of plastic to be placed in the mould. This can best be done by using a preforming machine which compresses the plastic into pellets of tablets of the appropriate size and weight. One or more pellets are then fed into the mould cavity giv

24、ing the exact volume of plastic required to fill the mould. A diagram of a closed mould is shown in Fig 11.10.In addition to performing, preheating is sometimes carried out in gas or electric ovens in order to partially soften the pellets. This is done for two reasons: (i) To reduce the cycle time a

25、nd increase the production rate by reducing the curing time in the press. (ii) To give easier flow characteristics to the polymer in the mould thus preventing damage to delicate moulds and small pins. This idea has led to the development of transfer moulding which can be regarded as mixture of compr

26、ession moulding and injection moulding. 压缩成型现在更经常使用不溢式压缩模，因为它不会在制品上产生恼人的飞边。它们要要求放到模具上的塑料要准备的量。通过使用一个预成型机，把塑料压缩到适当的大小和重量的塑料颗粒是很好的方法。然后把一个或更多的颗粒，送入给了确切的容量的模具模腔中，直到充满模具。一个封闭的模具图所示F11.10。除了预成型，有时在燃气或电烤炉内进行预热，以局部软化颗粒。这样做是出于两个原因：（一）为了减少周期时间，并通过减少在压缩成型中的固化时间来提高生产率。（二）在模具中提供聚合物更容易流动特性，从而防止精密模具和小型芯损坏。这种想法促进传

27、递模的发展，传递模可以看作是压缩成型和注射成型的综合混合物。This is an intermediate process in which extruded thermoplastic sections are reduced to sheets for example which may (or may not) then be formed to final shape by vacuum forming. As the plastic is being worked to shape at intermediate stage, calendering can only be used

28、 for thermoplastics and not thermosetting plastics.The process is similar in one way to the rolling of metal Fig 11.14(a) in that the material is compressed between rolls and emerges in the form of sheet. In every other way it is quite different because (i) the thermoplastic material swells apprecia

29、bly after it has passed through the position of minimum thickness which is directly on the vertical axis of the rolls Fig 11.14(b), and (ii) the pre-calendered material is not in sheet form but is in an extruded form of any given shape, or even in an unprocessed mass of indefinite shape.Fig 11.14(a)

30、 Rolling Metal Sheet 14 (b) Calendering of a ThermoplasticP.V.C, for example, is calendered into the well known transparent film widely used for packaging.这是一个中间工艺，其中部分热塑性塑料被挤掉最终形成板块，塑料可能（或可能不会）减少，然后将通过吸塑成型最终的形状。由于塑料是在一个中间阶段被加工，压延只能用于热塑性塑料而热固性塑料没有。这个工艺在某种方式上类似金属滚压图11.14（a），材料都是在两个辊轴之中被压，和成形板材的方法。在其他

31、各方面是完全不同的，因为：（一），在通过辊轴由垂直位置确定的最小厚度后，热塑性材料会膨胀图11.14（b），以及（ii）预压材料不是成型板料，而是挤出任何一个给定的形状，甚至挤压的形状是一个不确定未加工的形状。聚氯乙烯，例如，通过压延，可以制成著名的透明膜，广泛用于包装。This is a method of moulding thermoplastics which utilizes heat only, unlike injection moulding for example which utilizes both heat and pressure. Relatively, rotat

32、ional moulding is in its infancy, but is already used extensively for the production of toys such as beach balls hobby horses, boats, etc., in P.V.C . Polyethylene components such as containers, ducting, etc., are now successful produced by the process, including large components like laminates like

33、 laminated petrol tanks for motor cars made from polythene (outer shell) and nylon (inner shell). Development are taking place to enable a greater range of plastic to be used, and given the right material it is anticipated that a one piece motor car body shell could be produced in plastic by rotational mou