chapter1 MATERIALS AND THEIR PROPERTIES

null材料成型及控制专业英语概述材料成型及控制专业英语概述 材料成型及控制专业英语是该专业学生在通过基础英语学习阶段后，能够利用好英语而开设的，能使学生顺利阅读并正确理解有关专业书籍和文章的专业必修课程nullSpecialty English and College English (专业英语与大学英语 )基础进阶科技文献的阅读和翻译日常应用词汇、语法、句型null目的手段1.科技英语的语法特点1.科技英语的语法特点 词类转换多。所谓此类转换就是在翻译的过程中将英语中的某类词汇转换成汉语中的另外一类词汇。The operation of the machine needs some knowledge of its performance. 操作机器需要知道机器的性能。被动语态被动语态null科技英语中常用的被动句型科技英语中常用的被动句型科技英语中常用的被动句型后置定语多后置定语多 所谓后置定语，是指位于名词或代词之后的定语。由于科技英语的准确性与严密性，使其频繁使用后置定语．因此尽管定语是句子的次要成分，却是影响译文质量好坏的重要因素。复杂长句多复杂长句多 在翻译长句之前．常采用下列语法分析步骤： ①通读全句．以确定句子种类一一简单句、井列句、复合句． ②如为简单旬，则应先分析出主、渭、宾、表语（主要成分），再分析定语、状语等（次要成分）， 并弄清主次成分之间的关系，同时注意时态、语气和语态等． ③如为复合句，则应先找出主句，再确定从句及其性质．对于各从句，则分别按简单句分析． 英语长句的翻译方法概括起来有三种：顺译法、倒译法和分译法．null 虽然连续过程比间歇过程要求更为周密 设计 领导形象设计圆作业设计ao工艺污水处理厂设计附属工程施工组织设计清扫机器人结构设计 的设备。但连续过程通常能节约操作空间，较顺利地适应其它连续操作步骤。并能在任何常用的压力下进行，而不会暴露在大气中。2.科技英语构词法2.科技英语构词法所谓构词法即词的构成方法．即词在结构上的规律． 科技英语构词特点 1）外来语多（很多来自希腊语和拉丁语）； 2）构词方法多． 除了非科技英语中常用的三种构词法—转化、派生及合成法外，还普遍采用压缩法、混成法．符号法和宇母象形法． 3）有大量半科技英语词汇（semi-scientific words） annual output 年产量 produce…every year 2.1 转化法（conversion）2.1 转化法（conversion）2.2 派生法（derivation）2.2 派生法（derivation） 通过加前、后缀构成一个新词．2.3 合成法（composition）2.3 合成法（composition）由两个或更多的词合成一个词，叫合成法。有时需加连字符．2.4 压缩法（shortening）2.4 压缩法（shortening）只取词头字母 TOEFL： Test of English as a Foreign Language 非英语国家英语水平考试 ppm: parts per million 百万分之一 将单词删去一些字母： lab： laboratory 实验室 Kilo：kilogram 千克、公斤 nullCHAPTER 1 MATERIALS AND THEIR PROPERTIES1.1 Metals and Non-metals1.2 Ferrous Alloys 1.3 Non-Ferrous Alloys 1.4 Polymers1.1 Metals and Non-metals1.1 Metals and Non-metalsWords and Terms: mechanical property 机械（力学）性能 critical part and element 关键零部件 covalent bond 共价键 metalic bond金属键 crystal lattice 晶格 electrostatic attraction 静电吸引 plastic deformation 塑性变形 self-strengthening 自强化 stress oncentrator 应力集中点 the tip of a crack 裂纹尖端 1.1 Metals and Non-metals1.1 Metals and Non-metalsAmong numerous properties possessed by materials, their mechanical properties, in the majority of cases, are the most essential and therefore, they will be given much consideration in the book. All critical parts and elements, of which a high reliability is required， are made of metals, rather than of glass, plastics or stone.nullAs has been given in Fig. 1 - 1 metals are characterized by the metallic bond, where positive ions occupy the sites of the crystal lattice and are surrounded by electron gas. Fig. 1 - 1nullAll non-metals have an ionic or a covalent bond. These types of bond are rigid and are due to electrostatic attraction of two ions of unlike charges. nullBecause of the metallic bond, metals are capable of plastic deformation and self- strengthening upon plastic deformation. Therefore, if there is a defect in a material or if the shape of an element is such that there are stress concentrators, the stresses in these points may attain a great value and even cause cracking. nullIsometric (cubic)Isometric (cubic)Cubic unit cell axes are all THE SAME LENGTH a=b=c MUTUALLY PERPENDICULAR E.g.,“Fools Gold” is iron pyrite(黄铁矿), FeS2.nullnullHexagonal Close-Packed Crystal StructureThe hexagonal close-packed (hcp) crystal structure: (a) unit cell; and (b) single crystal with many unit cells. Hexagonal Close-Packed Crystal StructurenullBut since the plasticity of the material is high, the metal is deformed plastically in that point. say. at the tip of a crack, undergoes strengthening, and the process of fracture comes to an arrest.nullThis does not occur in non-metals. They are uncapable of plastic deformation and self- strengthening, therefore, fracture will occur as soon as the stresses at the tip of a defect exceed definite value. These facts explain why metals are reliable structural materials and can not be excelled by non-metallic materials. nullQuestions: I) What are the differences in properties between metals and non-metals? 2) Why are metals capable of plastic deformation and self-strengthening?Ferrous AlloysWords and Terms: ferrous 铁的；含铁的 corrosion resistance 耐腐蚀；抗蚀力 arbitrary 特定的；武断的 Ferrous AlloysFerrous AlloysFerrous AlloysMore than 90% by weight of the metallic materials used by human beings are ferrous alloys. This represents an immense family of engineering materials with a wide range of microstructure and related properties. Ferrous AlloysFerrous AlloysThe majority of engineering designs that require structural load support or power transmission involve ferrous alloys. as a practical matter, these alloys fall into two broad categories based on the carbon in the alloy composition. Ferrous AlloysFerrous AlloysSteel generally contains between 0.05 wt% and 2.0 wt% carbon. The cast irons generally contain between 2.0 wt% and 4.5 wt% carbon. nullIron-Iron carbide equilibrium diagram α-Fe0.006% 0.0218% δ-Fe Ferrous Alloys Within the steel category, we shall distinguish whether or not a significant amount of alloying elements other than carbon is used. 对于钢的区分，我们要弄清楚的是是否含有有效量的合金元素而不是碳的含量。 Ferrous AlloysFerrous AlloysFerrous AlloysA composition of 5 wt% total noncarbon additions will serve as an arbitrary boundary between low alloy and high alloy steels. Ferrous AlloysFerrous AlloysThese alloy additions are chosen carefully because they invariably bring with them sharply increased material costs. They are justified only by essential improvements in properties such as higher strength or improved corrosion resistance questionsquestionsHow do you distinguish steel from cast iron? How do you distinguish low alloy steel from high alloy steel?1.2.1 Plain Carbon iron Words and Terms: plain carbon steel hot-rolled steel bar beam sheet State Standard 1.2.1 Plain Carbon iron nullwelding forging stamping alloying element deoxidation harmful impurity1.2.1 Plain Carbon iron 1.2.1 Plain Carbon iron Hot-rolled steel delivered by steelmaking works as rolled sections (bars, beams, sheets, tubes, etc.) is the most wildly used material for manufacture of various machines, machine tools, building structures, consumer goods, etc. Delivered steel should have the properties as specified by State Standards.Recovery, Recrystallization and Grain Growth Schematic illustration of the effects of recovery, recrystallization, and grain growth on mechanical properties and shape and size of grains. Note the formation of small new grains during recrystallization. Recovery, Recrystallization and Grain GrowthCold, Warm and Hot WorkingHot working - above recrystallization temperature recrystallization, grain growth occurs Cold working - below recrystallization temperature no recrystallization or grain growth, significant grain elongation and work hardening results Warm working - intermediate temperature. Recrystallization occurs, but little or no grain growth. Grains are equiaxed but smaller than hot working.Cold, Warm and Hot Workingnullin the USSR, plain carbon steels are classified into three groups: A, B and C, depending on their application. A. if a steel is to be used for making products without hot working (welding, forging, etc.), its structure and properties in the final product will be the same as delivered from the rolling mill. In that case the user requests for a steel of warranted mechanical properties, while the chemical composition is not guaranteed.nullB. If a steel is to be subjected to hot working (forging, stamping, etc.), its initial structure and mechanical properties will be changed. In that case the composition of the steel will be of prime importance for the user, since it determines the conditions of hot working and the final mechanical properties of steel products. Now a steel of warranted composition is delivered to the user.nullC. If a steel is to be welded, the user wants to know the composition of the steel, since it determines the properties of the metal in the zone subjected to thermal effect of weld.The user is also interested in the initial mechanical properties of the metal, since these properties will remain the same in portions not subjected to welding. in that case the metal is delivered with warranted composition and mechanical properties.nullGeneral-purpose plain steels are not alloyed. Some alloying elements may sometimes be present in them occasionally and their content is limited. nullThe presence of silicon and manganese may be due to the steel-making process (the necessity of deoxidation). Sulphur and phosphorus are harmful impurities in steel and their content should be minimized as it may affect the quality of steel. nullThe principal element whose content is responsible for the properties of steels is carbon.nullQuestions: 1) What group of steels should be selected if the steels will be subjected to welding?1.2.2 Low Alloy SteelsLow alloy steel ductile eminently proprietary HSLA stress relief1.2.2 Low Alloy Steels1.2.2 Low Alloy Steels1.2.2 Low Alloy SteelsThe majority of ferrous alloys belongs to this category. The reasons for this are straightforward. They are moderately priced due to the absence of large amounts of alloying elements, and they are sufficiently ductile to be readily formed. nullThe final product is strong and durable. These eminently practical materials find applications from ball bearings to metal sheets formed into automobile bodies. nullThe designation of ferrous alloys is specified by digits such as 1OXX, 11XX, 12XX, 15XX etc. (AISI standards, in which the first two numbers gives a code designating the type of alloying additions and the last two or three numbers give the carbon content in hundredths of a weight percent). nullAs an example, the plain carbon steel with 0.40 wt% carbon is a 104() steel, whereas a steel with 1.45 wt% Cr and 1.50 wt% carbon is a 52150 steel. One should keep in mind that chemical compositions quoted in alloy designations are approximate and will vary slightly from product to product within acceptable limits of industrial quality control.nullAn interesting class of alloys known as high strength low alloy (HSLA) steels has emerged in response to requirements for weight reduction of vehicles. The composition of many commercial HSLA steels are proprietary and specified by mechanical properties rather than composition. nullBut typical example might contain 0.2 wt % carbon and about 1 .0 wt % or less of such elements as Mn, Si, Cr, W, Ni or Mo. The strength of HSLA steels is the result of optimal alloy selection and carefully controlled processing such as hot rolling (deformation at temperatures sufficiently elevated to allow some stress relief). nullQuestions: 1) What is the difference between the carbon steel and HSLA steel? 2) Why is the HSLA steel so popular? 3) How are the good properties of the HSLA steel obtained?