机械工程英语翻译.doc

Powder metallurgy(Fig.5.1) uses sintering process for making various parts out of metal powder. The metal powder is compacted by placing in a closed metal cavity (the die) under pressure. 粉末冶金(图5.1)采用烧结工艺将金属粉末制成各种各样的零件。金属粉末放在封闭的金属腔(模具)中在压力下被压实。This compacted material is placed in an oven and sintered in a controlled atmosphere at high temperatures and the metal powders coalesce and form a solid. A Second pressing operation, repressing, can be done prior to sintering to improve the compaction and the material properties.被压实的材料置于炉内烧结，在高温下炉内环境可控，金属粉末熔合形成固体。在烧结前可以进行二次挤压作业(再挤压)以改善压实状态和材料性能。 Powder metallurgy is a highly developed method of manufacturing reliable ferrous and nonferrous parts. Made by mixing elemental or alloy powders and compacting the mixture in a die, the resultant shapes are then sintered or heated in a controlled atmosphere furnace. 粉末冶金是一种高度发达的制造可靠铁或非铁零件的方法。通过混合元素或合金粉末并在模具中压实混合物，再烧结或在环境可控炉内加热制成最终形状。 Material 材料 The majority of the structural components produced by fixed die pressing are iron-based. The powders are elemental, pre-alloyed, or partially alloyed. 大多数用固定模压制的结构件都是铁基的。粉末可以是单一元素、预先合金或部分合金。Elemental powders, such as iron and copper, are easy to compress to relatively high densities, produce pressed compacts with adequate strength for handling during sintering, but do not produce very high strength sintered parts.诸如铁、铜之类的单一元素粉末较容易被压得相对密度较高、生产具备足够强度的压制物供烧结处理，但是无法制造出很高强度的烧结零件。 Pre-alloyed powders are harder, less compressible and hence require higher pressing loads to produce high density compacts. However, they are capable of producing high strength sintered materials. 预先合金粉末比较硬、不容易压实，因此需要较高的挤压力来产生高密度的压制物。然而它们能生成高强度烧结材料。Pre-alloying is also used when the production of a homogeneous material from elemental powders requires very high temperatures and long sintering times. The best examples are the stainless steels, whose chromium and nickel contents have to be pre-alloyed to allow economic production by powder metallurgy.如果用单一元素粉末生产均匀材料需要很高温度和较长烧结时间，也可用预先合金。最好的例子是不锈钢，因含有铬和镍成分，所以粉末冶金必须用预先合金才经济。 Partially alloyed powders are a compromise approach. Elemental powders, e.g. iron with 2wt.% copper, are mixed to produce an homogeneous blend which is then partially sintered to attach the copper particles to the iron particles without producing a fully diffused powder but retaining the powder form. 部分合金粉末是一种折衷的方法。单一元素粉末，例如铁与2%的铜(重量百分比) 混合均匀，经部分烧结后铜微粒粘附到铁微粒上而没有产生充分扩散的粉末却保留了粉末的形态。In this way the compressibilities of the separate powders in the blend are maintained and the blend will not segregate during transportation and use.用这种方法混合物中单独粉末的可压缩性得以维持，在运送和使用期间结合将不会分离。 A similar technique is to “glue” the small percentage of alloying element onto the iron powder. This “glueing” technique is successfully used to introduce carbon into the blends, a technique which prevents carbon segregation and dusting, producing so-called “clean” powders. 另一种类似的技术是把小百分比的合金元素“粘合”到铁微粒上。这种“粘合”技术已成功用于将碳引入结合物，一种防止碳分离并起尘的技术，生产所谓的“清洁”粉末。 Powder Consolidation粉末合成 Components or articles are produced by forming a mass of powder into a shape, then consolidating to form inter-particle metallurgical bonds. 通过将大量的粉末放入模具成型为零件或物品，然后合成为内有微粒的冶金结合物。An elevated temperature diffusion process referred to as sintering, sometimes assisted by external pressure, accomplishes this. The material is never fully molten, although there might be a small volume fraction of liquid present during the sintering process. Sintering can be regarded as welding the particles present in the initial useful shape.提升温度扩散工艺被称为烧结，有时还辅之以外界的压力来达到目的。虽然在烧结过程中可能会有少量液态出现，但材料决不是全熔化。烧结可以被看作是把微粒焊接成初始的有用形状。 As a general rule both mechanical and physical properties improve with increasing density. Therefore the method selected for the fabrication of a component by powder metallurgy will depend on the level of performance required from the part. Many components are adequate when produced at 8590% of theoretical full density whist others require full density for satisfactory performance. 作为普遍规律，随着密度的增加机械和物理性能均改善。因此选择何种粉末冶金方法来制作零件取决于其所需的性能级别。许多零件只需理论全密度的8590%而其它的则需全密度才能满足要求。 Some components, in particular bush type bearings often made from copper and its alloys, are produced with significant and controlled levels of porosity, the porosity being subsequently filled with a lubricant. Fortunately there is a wide choice of consolidation techniques available. 有些零件，尤其是衬套式轴承常用铜及其合金制作，控制多孔性程度的意义重大，因为这些孔随后要填充润滑剂。 还好有多种合成技术可供选择。Cold Uniaxial Pressing Elemental metal, or an atomized pre-alloyed powder is mixed with a lubricant, typically lithium stearate(0.75 wt.%), and pressed at pressures of say, 600MPa (87,000lb/in.2) in metal dies. 冷单向挤压 单一元素金属，或极小颗粒的预先合金粉末与润滑剂(一般是锂硬脂酸盐，重量百分比0.75%)混合，然后在金属模具中施加压力比如600MPa (87,000lb/in.2)挤压。Cold compaction ensures that the as-compacted, or “green”, component is dimensionally very accurate, as it is moulded precisely to the size and shape of the die. 冷挤压能保证被压制或“未加工”的零件尺寸十分精确，因为它被精确地按模具的尺寸和形状成型。 One disadvantage of this technique is the differences in pressed density that can occur in different parts of the component due to particle/particle and die wall/particle frictional effects. Typical as-pressed densities for soft iron components would be 7.0g/cc, i. e. about 90% of theoretical density. 这种技术的缺点之一是由于微粒/微粒和模壁/微粒间的摩擦效应，零件不同部位的压实密度存在差异。典型的软铁零件压制密度为7.0g/cc，即大约是理论密度的90%。Compaction pressure rises significantly if higher as-pressed densities are required, and this practice becomes uneconomic due to higher costs for the larger presses and stronger tools to withstand the higher pressures.如果需要较高的压实密度则压实压力要显著提高，因为大型压力机成本较高并且在较高压力下模具强度要更高这样就不合算。Cold Isostatic Pressing Metal powders are contained in an enclosure e.g. a rubber membrane or a metallic can that is subjected to isostatic, which is uniform in all directions, external pressure. As the pressure is isostatic the as-pressed component is of uniform density.冷均衡挤压 金属粉末装入均衡受压的橡胶膜或金属罐内，其所受外压力在各个方向都是均匀的。由于压力是均衡的，所以压制零件密度是均匀的。Irregularly shaped powder particles must be used to provide adequate green strength in the as-pressed component. This will then be sintered in a suitable atmosphere to yield the required product.必须采用不规则形状粉末微粒为压制零件提供足够的未加工强度。然后放入合适的环境中烧结成所需产品。 Normally this technique is only used for semi-fabricated products such as bars, billets, sheet, and roughly shaped components, all of which require considerable secondary operations to produce the final, accurately dimensioned component. 通常这种技术只用于制作诸如棒料、坯段、薄板及粗糙成型零件之类的半成品，所有这些都需要大量进一步加工才能生产出最终尺寸精确的零件。Again, at economical working pressures, products are not fully dense and usually need additional working such as hot extrusion, hot rolling or forging to fully density the material.此外使用经济工作压力的产品不是充分致密的，一般需要增加诸如热挤压、热轧或锻之类的额外工序来使材料达到全密度。Sintering Sintering is the process whereby powder compacts are heated so that adjacent particles fuse together, thus resulting in a solid article with improved mechanical strength compared to the powder compact. 烧结 烧结就是通过把粉末压制物加热使邻近的微粒熔合在一起的工艺，它能生成比粉末压制物机械强度更好的固体物。This “fusing” of particles results in an increase in the density of the part and hence the process is sometimes called densification. There are some processes such as hot isostatic pressing which combine the compaction and sintering processes into a single step.微粒的“熔合”导致零件密度增加，因此该工艺有时被称为致密化。还有一些工艺如热均衡挤压，将压实和烧结工艺合并为单一步骤。 After compaction the components pass through a sintering furnace. This typically has two heating zones, the first removes the lubricant, and the second higher temperature zone allows diffusion and bonding between powder particles. 零件压实后通过烧结炉。一般有两个加热区，第一个去除润滑剂，第二个温度更高的区域让粉末微粒之间扩散并结合。A range of atmospheres, including vacuum, are used to sinter different materials depending on their chemical compositions. As an example, precise atmosphere control allows iron/carbon materials to be produced with specific carbon compositions and mechanical properties.根据不同材料的化学成分，烧结的环境包括真空状态也各不相同。例如精确的环境控制可使铁/碳材料生成特殊碳化物和机械性能。 The density of the component can also change during sintering, depending on the materials and the sintering temperature. These dimensional changes can be controlled by an understanding and control of the pressing and sintering parameters, 根据材料和烧结温度的不同，零件的密度在烧结过程中也会改变。因为尺寸的变化可以通过了解并调节挤压及烧结参数进行控制，and components can be produced with dimensions that need little or no rectification to meet the dimensional tolerances. Note that in many cases all of the powder used is present in the finished product, scrap losses will only occur when secondary machining operations are necessary.所以零件尺寸几乎无需校正就能满足尺寸公差。可以看到在很多情况下所有使用的粉末都包含在制成品中，废料损失仅产生于需要辅助机加工时。Hot Isostatic Pressing Powders are usually encapsulated in a metallic container but sometimes in glass. The container is evacuated, the powder out-gassed to avoid contamination of the materials by any residual gas during the consolidation stage and sealed-off. 热均衡挤压 粉末通常封装在金属容器内有时也装在玻璃容器内。把容器抽真空，粉末抽气是为了防止材料在合成阶段和密封时被残留气体污染。It is then heated and subjected to isostatic pressure sufficient to plastically deform both the container and the powder.再加热并施加均衡压力足以使容器和粉末都塑性变形。 The rate of densification of the powder depends upon the yield strength of the powder at the temperatures and pressures chosen. At moderate temperature the yield strength of the powder can still be high and require high pressure to produce densification in an economic time. 粉末致密率取决于该粉末在选定温度和压力下的屈服强度。中等温度下粉末的屈服强度仍然较高，因此需要较高压力使其在经济时间内致密化。Typical values might be 1120 and 100MPa for ferrous alloys. By pressing at very much higher temperatures lower pressures are required as the yield strength of the material is lower. Using a glass enclosure atmospheric pressure(15psi) is used to consolidate bars and larger billets.对铁合金典型的数值为1120和100MPa。由于很高温度下材料的屈服强度较低，因此只需较低压力就能挤压。采用玻璃容器时可用大气压力(15psi)合成棒料和较大坯段。 The technique requires considerable financial investment as the pressure vessel has to withstand the internal gas pressure and allow the powder to be heated to high temperatures. 因为压力容器必须经受住内气压并允许粉末加热到较高温度，所以这种技术需要相当可观的资金投入。 As with cold isostatic pressing only semi-finished products are produced, either for subsequent working to smaller sizes, or for machining to finished dimensions. 此工艺与采用冷均衡挤压一样只能生产半成品，可以通过后续加工至较小尺寸，也能用机加工到最终尺寸。Hot Forging (Powder Forging) Cold pressed and sintered components have the great advantage of being close to final shape (near-net shape), but are not fully dense. Where densification is essential to provide adequate mechanical properties, the technique of hot forging, or powder forging, can be used.热锻(粉末锻造) 冷挤压和烧结零件主要优点是接近最终形状(近似纯形)，但不是充分致密的。当为了提供足够的机械性能而致密化是必须时，可以采用热锻或粉末锻造技术。 In powder forging an as-pressed component is usually heated to a forging temperature significantly below the usual sintering temperature of the material and then forged in a closed die. This produces a fully dense component with the shape of the forging die and appropriate mechanical properties. 在粉末锻造中，压制零件一般加热到远低于该材料通常烧结温度的锻造温度，然后在闭模中锻造。这能生产具有锻模形状和合适机械性能的充分致密零件。 Powder forged parts generally are not as close to final size or shape as cold pressed and sintered parts. These results from the allowances made for thermal expansion effects and the need for draft angles on the forging tools. Further, minimal machining is required but when all things are considered this route is often very cost-effective. 粉末锻造零件通常不像冷挤压和烧结零件那样接近最终尺寸或形状。这是由于为热膨胀效应而设置允差以及在锻模上需要拔模斜角所致。此外还需少量机加工，但全面考虑这种方法通常还是很划算的。Metal Injection Moulding (MIM) Injection moulding is very widely used to produce precisely shaped plastic components in complex dies. As injection pressures are low it is possible to manufacture complex components, even some with internal screw threads, by the use of side cores and split tools.金属注塑成型(MIM) 注塑成型被很广泛地用于在复杂模具中生产形状精确的塑料零件。注塑压力较低使得制作复杂零件成为可能，通过采用侧面型芯和分离工具甚至可以带有内螺纹。 By mixing fine, typically less than 20 m diameter, spherical metal powders with thermoplastic binders, metal filled plastic components can be produced with many of the features available in injection moulded plastics. After injection moulding, the plastic binder material is removed to leave a metal skeleton which is then sintered at high temperature. 将细小(直径一般小于20m)球形金属粉末与热塑性粘合剂混合，能生产具有多数注塑成型塑料特征的金属充满塑料零件。注塑成型后，去除塑料粘合材料剩下金属骨架，然后在高温下烧结。 Dimensional control can be exercised on the as-sintered component as the injected density is sensibly uniform so shrinkage on sintering is also uniform. 烧结零件可以实现尺寸控制，因为注塑密度明显均匀，所以烧结收缩也是均匀的。 Shrinkage can be large, due to both the fine particle size of the powders and the substantial proportion of polymer binder used. 由于所用粉末细小微粒的尺寸和聚合物粘合剂的真实比例，收缩可以比较大。 Features 特征 For high tolerance parts, a sintering part is put back into a die and repressed. In genera this makes the part more accurate with a better surface finish. 对较大公差的零件，烧结后可放回模具重新挤压。一般而言这会使零件更精确同时具有更好的表面光洁度。 A part has many voids that can be impregnated. One method is to use an oil bath. Another method uses vacuum first, then impregnation. 零件有许多可供填充的空间。一种方法是采用油浴。另一种方法是先抽真空然后再充满。 A part surface can be infiltrated with a low melting point metal to increase density, strength, hardness, ductility and impact resistance. Plating, heat treating and machining operations can also be used. 零件表面能被低熔点金属渗透以增大密度、强度、硬度、延展性和抗冲击能力。 仍然可以进行电镀、热处理和机加工作业。 Advantages 优点 Good tolerances and surface finish Highly complex shapes made quickly Can produce porous parts and hard to manufacture materials (e.g. cemented oxides) 良好的公差和表面光洁度 高度复杂的形状能快速制作 能制作多孔零件和难以加工材料(如粘结氧化物) Pores in the metal can be filled with other materials/metals Surfaces can have high wear resistance Porosity can be controlled Low waste Automation is easy 金属中的气孔可用其它材料/金属填充 表面能具有较高的耐磨性 孔隙率可以控制 较低损耗 容易自动化 Physical properties can be controlled Variation from part to part is low Hard to machine metals can be used easily No molten metals 物理性能可以控制 零件之间的变化较小 难以机加工的金属能被容易使用 无需熔化金属 No need for many/any finishing operations Permits high volume production of complex shapes Allows non-traditional alloy combinations Good control of final density 不需要很多/任何修整作业 允许加工复杂形状的大体积产品 允许非传统合金结合 对最终密度能很好地控制 Disadvantages 缺点 Metal powders deteriorate quickly when stored improperly Fixed and setup costs are high Part size is limited by the press and compression of the powder used 如果存放不当金属粉末质量很快降低 安装和调整的成本较高 零件尺寸受压力机和所用粉末压缩的限制 Sharp corners and varying thickness can be hard to produce Non-moldable features are impossible to produce 锐角和变厚度较难加工 不适合模压的东西不可能生产 Injection molding (Fig.6.1) is the predominant process for fabrication of thermoplastics into finished forms, and is increasingly being used for thermosetting plastics, fiber-filled composites, and elastomers. 注塑成型(图6.1)是将热塑性塑料制成最终形状的主要工艺，并且越来越多地用于热硬化性塑料、纤维填充合成物和人造橡胶。 It is the process of choice for tremendous variety of parts ranging in weight from 5g to 85kg. It is estimated that 25% of all thermoplastics are injection molded. 它是重量范围为5g到85kg极大一类零件可选用的工艺。估计所有热塑性塑料中有25%是采用注塑成型的。If newer modifications, such as reaction injection molding, and the greatly increased rate of adoption of plastics as substitutes for metals are considered, it is likely that the worldwide industrial importance of injection molding will continue to increase. 如果考虑到新近的改进(例如反作用注塑成型)和采用塑料替代金属的高增长率，注塑成型在世界范围的工业重要性很可能将继续增加。Currently, probably close to half of all major processing units is injection molding machines. In 1988, a dollar sale of new injection molding machinery in the U.S. was approximately 65% of total major polymer machinery sales volume; this included 4,600 injection molding units. 当前，大概所有主要处理设备的近一半是注塑成型机。1988年，美国新的注塑成型机械销售约占全部主要聚合物机械销售量的65%，其中包括4,600台注塑成型设备。The machines and their products are ubiquitous and are synonymous with plastics for many people.这类机械和它们的产品普遍存在，对许多人来说与塑料是同义的。 A reciprocating screw injection molding machine combines the functions of an extruder and a compressive molding press. 往复螺旋注射成型机把压出机和成型压力机的功能结合起来。It takes solid granules of thermoplastic resin, melts and pressurizes them in the extruder section, forces the melt at high velocity and pressure through carefully designed flow channels into a cooled mold, then ejects the finished part(s), and automatically recycles. 把热塑性塑料树脂的固体颗粒在压出部分融化并增压，迫使其高速融化并通过仔细设计的流动通道进入冷却模具，喷射成最终零件，然后自动再循环。This machine is a descendant of the plunger type “stuffing machine” patented by the Hyatt brothers in 1872 to mold celluloid. In 1878, the Hyatts developed the first multicavity mold, but it was not until 1938 that Quillery (France) patented a machine incorporating a screw to plasticize the elastomer being molded.这种机械是1872年Hyatt兄弟获得专利权的融化赛璐珞的活塞型“填充机”的派生物。 1878年Hyatt兄弟开发了第一个多槽模具，但直到1938年Quillery(法国)才发明了用螺旋增塑人造橡胶并使其成型的一体化机械。In 1956, Ankerwerk Nuremberg commercialized the modern reciprocating screw injection molding machine for thermoplastics. Today, over 50 machine manufacturers are listed in Modern Plastics Encyclopedia, offering machines to the U.S. market ranging from 2 to 6,000 tons clamping capacity. 1956年，Ankerwerk Nuremberg使用于热塑性塑料的现代往复螺旋注塑成型机商业化。今天，已有超过50家制造商列入现代塑料制品百科全书，能为美国市场提供压制能力从2到6,000吨的机械。(A machine with a 10,000-ton capacity has been built to mold 264-gallon HDPE trash containers.) A host of suppliers of auxiliary equipment, molds, instruments, and controls service this major segment of the polymer industry.(一台能力为10,000吨用于成型264加仑高密度聚乙烯