【正文】 ed, it may be necessary to anneal（退火） before proceeding, that is（換句話說）, if the piece is given time to workharden. This may not be a scientific statement, but it is actually what seems to happen.在這方面，相當(dāng)有趣的是你將發(fā)現(xiàn)有時可通過一次快速加載完成大拉伸，但以緩慢的方式兩三次加載卻不能實(shí)現(xiàn)。經(jīng)過熱處理的工件像我們看到的那樣會發(fā)生嚴(yán)重的翹曲，但是我們?nèi)匀幌Ｍぜ蝗拥綗崽幚頎t中被處理，這樣好過它存在內(nèi)應(yīng)力的狀態(tài)。由于周圍金屬的較高溫度，當(dāng)焊接弧移開焊接點(diǎn)后，冷卻速度不會太快，產(chǎn)生了低速冷卻的結(jié)果。s?lf?]（硫磺） in steel.加工性不僅僅只由硬度決定，它還由韌性，微觀結(jié)構(gòu)，化學(xué)成分和在冷加工下金屬所呈現(xiàn)的硬化特性所決定。 In the machining of metal, the metal being cut, the cutting tool, the coolant, the process and type of machine tool（機(jī)床）, and the cutting conditions all influence the results. By changing any one of these factors, different results will be obtained. The criterion [krai39。鋼的淬透性是鋼材本身所固有的屬性，它只取決于其本身的內(nèi)部因素，而與外部因素?zé)o關(guān)?！　?鋼的原始組織的粗細(xì)和分布對奧氏體的成分將有重大影響。2Mn 在鋼中形成MnS以代替FeS。4 Cr 鉻在鋼中形成較穩(wěn)定的碳化物，提高碳化物在鋼中的溶解溫度，減慢溶解速度。7 W 與碳形成穩(wěn)定的碳化物提高鋼的熱強(qiáng)性，增大變形抗力8 Cu 銅在鋼中可溶于鐵素體中，也可沿晶界析出游離銅%Cu時，加熱不當(dāng)，表面易生裂紋，高溫軋制時易產(chǎn)生熱脆9 B 硼能細(xì)化晶粒，能溶解在γ和α固溶體中，與Fe化合成Fe2B鋼中含B＞%時，鍛造易裂10 S 在鋼中形成硫化物或共晶體，如FeS、Fe的熔點(diǎn)為985℃，且成網(wǎng)狀布于晶界顯著降低可鍛性（紅脆）11 P 促成偏析，使晶粒粗大，容易引起鍛件表面龜裂降低可鍛性Unit 3 Mechanical Properties of MaterialsThe material properties can be classified into three major headings: (i) Physical, (ii) Chemical, (iii) Mechanical.Physical propertiesDensity or specific gravity, moisture [39。zibit]n. 展覽品；證據(jù)；展示會vt. 展覽；顯示；提出（證據(jù)等）vi. 展出；開展覽會 clear ranges of elasticity, copper, zinc（鋅）, tin（錫）, etc, are found to be imperfectly[im39。其中包括酸性或堿性，活性和耐腐蝕性。在應(yīng)力應(yīng)變曲線中，直線關(guān)系和隨后的小小的彎曲描述了上述的加載和卸載。 當(dāng)在彈性極限之上增大載荷時會產(chǎn)生塑性變形。在T點(diǎn)試件斷裂，此時的載荷稱為斷裂載荷。這種現(xiàn)象一直持續(xù)到曲線上的S點(diǎn)。負(fù)責(zé)新機(jī)器的設(shè)計最初的最重要的是經(jīng)濟(jì)性考慮。零件的結(jié)構(gòu)和尺寸通常根據(jù)實(shí)際考慮。例如，從設(shè)計理念到設(shè)計分析的每一個階段，制造，市場，銷售。環(huán)境影響 ⑧Reliability and life。設(shè)計一臺新機(jī)器時，關(guān)鍵件具有足夠的抵抗破壞的能力是非常重要的。例如，汽車的冷卻系統(tǒng)的散熱器皮帶管松開。有時，一次失敗是嚴(yán)重的，例如高速行駛的汽車的輪胎爆裂。沖擊力 ④ Applied with continuous direction reversals。制造 ⑥ Safety。設(shè)計和構(gòu)建布局要完全詳細(xì)地說明每一個細(xì)節(jié)，并且對最終產(chǎn)品進(jìn)行必要的測試。他們都符合不同的設(shè)想，這必須由工程量決定。 Unit5 Design of machine and machine elements機(jī)器和機(jī)器零件的設(shè)計Machine design機(jī)器設(shè)計Machine design is the art of planning or devising new or improved machines to acplish specific purposes. In general, a machine will consist of a bination of several different mechanical elements properly designed and arranged to work together, as a whole. During the initial planning of a machine, fundamental decisions must be made concerning loading, type of kinematic elements to be used, and correct utilization of the properties of engineering materials. Economic considerations are usually of prime importance when the design of new machinery is undertaken. In general, the lowest overall costs are designed. Consideration should be given not only to the cost of design, manufacture the necessary safety features and be of pleasing external appearance. The objective is to produce a machine which is not only sufficiently rugged to function properly for a reasonable life, but is at the same time cheap enough to be economically feasible.機(jī)器設(shè)計為了特定的目的而發(fā)明或改進(jìn)機(jī)器的一種藝術(shù)。） 由于加工硬化，金屬在發(fā)生塑性變形時會變得越來越硬。 試件從Q到S在到T不斷地延長。 鐵和鎳存在明顯的彈性范圍，銅，鋅，錫等即使在相當(dāng)?shù)偷膽?yīng)力值下彈性也表現(xiàn)得不是很充分。當(dāng)卸載時，變形消失。物理特性 密度或特定的重力，濕度等都屬于此范疇。sis?] n. [數(shù)]橫坐標(biāo)；橫線) in a tensile test. A material tends to change or changes its dimensions when it is loaded, depending upon the magnitude大小 of the load. When the load is removed it can be seen that the deformation disappear s. For many materials this occurs up to一直到；相當(dāng)于；忙于，在做；由決定的 a certain value of the stress called the elastic limit. This is depicted by the straight line relationship and a small deviation[,di:vi39。這些鋼在空冷時間淬火，要防止冷裂。珠光體Ni鋼在鍛造時易形成片狀破裂和帶狀組織。所有碳化物都有硬度高、塑性低、熔點(diǎn)高的特點(diǎn)，但滲碳體型碳化物在加熱到鍛造溫度時經(jīng)適當(dāng)保溫可大部分或全部溶入固溶體中，而合金碳化物較難溶入固溶體中，對鋼的可鍛性影響最大。但晶粒粗大將增大鋼的變形、開裂傾向和降低韌性。鋼材淬透性好與差，常用淬硬層深度來表示。Machinability is a term used to indicate the relative（比較的） ease（不費(fèi)力） with which a material can be machined by sharp cutting tools in operations such as turning（車）, drilling（鉆）, milling（銑）, broaching[39。s230。預(yù)熱可以取得與之相當(dāng)?shù)男Ч?。When doubt exists as to（關(guān)于） whether internal stresses will cause warpage, a piece can be checked by heating it to about 1100 and then letting it cool. If there are internal stresses, the piece is likely to（可能） deform. Pieces that will warp severely while being heated have been seen, yet （然而）the heattreater熱處理爐 was expected to有望做某事；被期待做某事 put them throughput through 完成 and bring them out better than they were in the first place.當(dāng)是否內(nèi)應(yīng)力會引起翹曲的懷疑存在時，可以通過將工件加工至1100然后進(jìn)行冷卻來驗(yàn)證。加工力的大小取決于屈服點(diǎn)，因?yàn)殇撛谇c(diǎn)之上才開始變形。lb=) blowat a single blow= at one blowat a single blow:一下子|一舉|一擊 as plain steels of similar carbon content. Nickel decreases forgeability of mediumcarbon steels, but has little effect on lowcarbon steels. Chromium seems to harden steel at forging temperatures, but vanadium(釩) has no discernible(可辨別的) effect。Considerations in fabrication(制造)The properties of the final part (hardness, strength, and machinability [m?,?i:n?39。bil?ti]是產(chǎn)品在被調(diào)用時能夠運(yùn)行（即未處于失效或修復(fù)狀態(tài)）的概率。例如，鎳合金主要用于抗磨損和耐高溫的用途，由于鈦合金具有高強(qiáng)度和低密度的綜合特性，鈦被廣泛應(yīng)用于航空工業(yè)中。不管怎樣，如果想使一種金屬或合金在使用中表現(xiàn)出穩(wěn)定一致的特性，在其中添加何種化學(xué)成分，它的量多大都應(yīng)該在控制范圍之內(nèi)。實(shí)際應(yīng)用中的金屬往往都包含著一定數(shù)量的一種或多種外來金屬或非金屬元素，這些外來元素可能是有害的也可能是有益的或者它們對某種特定的屬性沒有影響。原子間距隨著原子大小呈規(guī)律性變化，原子間距是金屬的一種特性。然而，在實(shí)際應(yīng)用中，可以將具有某些特性集合金屬定義為某種元素。2. Suffice it to say that the gun was his.只需說這槍是他的就夠了。lin?ti]. A crystalline solid is one in which the constituent atoms are located in a regular threedimensional array as if they were located at the corners of the squares of a threedimensional chessboardn. 棋盤. The spacing of the atoms in the array is of the same order as the size of the atoms, the actual spacing being a characteristic of the particular metal. The directions of the axes of the array define the orientation of the crystal in space. The metals monly used in engineering practice are posed of a large number of such crystals, called grains晶粒. In the most general case一般情況下, 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