【正文】 這些金屬涉及的范圍從含碳90%以上的鑄鐵和碳鋼到特種鐵合金，在這些鐵合金中，各種其他元素的總和幾乎占總成分一半。 There are two families of metallic materials: ferrous and nonferrous. The basic ingredient of all ferrous metals is the element iron. These metals range from cast irons and carbon steels, which 90% iron, to specialty iron alloys, containing a variety of other elements that add up to nearly half the total position. 金屬材料分為兩類：黑色金屬和有色金屬。當(dāng)金屬已經(jīng)以固體的形式存在或形成時(shí)，并且是塑性的，被稱為可鍛金屬。同樣，電子云使大多數(shù)金屬有很好的導(dǎo)電性和導(dǎo)熱性。由于這些自由電子對(duì)帶正電的金屬原子或離子有靜電吸引力，因此可以將晶體結(jié)構(gòu)緊湊的結(jié)合在一起。單個(gè)晶體是由單元晶粒按有規(guī)則模式重復(fù)而形成的三維晶格。金屬合金由兩種或兩種以上的元素組成，用途非常廣泛，正是由于這種結(jié)構(gòu)上的原因，很多金屬被用于工業(yè)上。盡管嚴(yán)格定義的金屬只局限于純金屬，但是普遍的用法是把它擴(kuò)展到更廣范圍的金屬合金。當(dāng)時(shí)取得最大值。Substitution in equations () and () gives: 代入方程（）和（）得： ()Sphere()球（） hence:于是: ()Cone()圓錐（）A cone is swept put by a straight line included at an angle to the axis.圓錐是由一條直線以一定的角度繞軸旋轉(zhuǎn)而成的。那么元件上的法向力（垂直于表面的分力）This force is resisted by the normal ponent of the forces associated with the membrane stresses in the walls of vessel （given by, force=stressarea） 通過與容器器壁的薄膜應(yīng)力聯(lián)系的法向力來抵抗這個(gè)力（即，力=應(yīng)力*面積）Equating these forces and simplifying, and noting that in the limit , and , gives:假設(shè)這些力是相等的并簡(jiǎn)化，取極限, 和，有 ()An expression for the meridional stress can be obtained by considering the equilibrium of the forces acting about any circumferential line, Fig . The vertical ponent of the pressure force經(jīng)向應(yīng)力的一個(gè)表達(dá)式可由作用在周向線上力的平衡得到，This is balanced by the vertical ponent of the force due to the meridional stress acting in the ring of the wall of the vessel=2σ1tл(r2sinθ) sinθ這與作用在容器壁上的經(jīng)向力的垂直分力是平衡的 =2σ1tл(r2sinθ) sinθEquating these forces gives:令這兩個(gè)力相等有： ()Equations () and () are pletely general for any shell of revolution.方程（）和（）對(duì)所有的回轉(zhuǎn)殼都適用。 the values of and are determined by the shape.注意：容器有兩個(gè)曲率；r1 和r2值由模型決定。 that is, the load per unit area (pressure) on the shell is constant round the circumference, but not necessarily the same from top to bottom.，研究的是回轉(zhuǎn)殼一般模型在旋轉(zhuǎn)軸對(duì)稱的載荷作用下的情行；也就是，單位圓周面積上的載荷是一定的，但不都是從上到下。實(shí)際所需壁厚也依賴于容器上所受其他載荷引起的應(yīng)力。 similar to the walls of a balloon.薄容器的器壁可以看成是“薄膜”；假設(shè)載荷沒有明顯撓度和剪應(yīng)力；就像氣球的薄膜。大多數(shù)過程容器是由回轉(zhuǎn)殼組成的：圓柱和圓錐形的；半球形的；橢球形的和準(zhǔn)球形的；. The walls of thin vessels can be considered to be “membranes”。 and hemispherical, ellipsoidal and torispherical heads。 Unit 4 Membrane Stresses in Shells of Revolution回轉(zhuǎn)殼的薄膜應(yīng)力A shell of revolution is the form swept out by a line or curve rotated about an axis (A solid of revolution is formed by rotating an area about an axis). Most process vessels are made up from shells of revolution。 橫截面積減小的速度非?？?；以至于實(shí)際上載荷降低。應(yīng)變變得很大，面積的減少在某些點(diǎn)產(chǎn)生了局部效應(yīng)。這種現(xiàn)象一直持續(xù)到曲線上的S點(diǎn)。） 由于加工硬化，金屬在發(fā)生塑性變形時(shí)會(huì)變得越來越硬。這種現(xiàn)象的發(fā)生可能有兩種原因：1. 材料的應(yīng)變強(qiáng)化；2. 由于塑性變形引起的試件橫截面積的縮小。 邏輯上來說，一旦超過彈性極限，金屬應(yīng)該就會(huì)屈服直至最后斷裂，在應(yīng)力值上應(yīng)該沒有增加。在T點(diǎn)試件斷裂，此時(shí)的載荷稱為斷裂載荷。 試件從Q到S在到T不斷地延長(zhǎng)。一開始一直在抵抗載荷的金屬在這一點(diǎn)后開始迅速地發(fā)生形變，也就是，屈服。到達(dá)某點(diǎn)后變形的速度快于載荷增加的速度。 當(dāng)在彈性極限之上增大載荷時(shí)會(huì)產(chǎn)生塑性變形。 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。這可能是由于材料回復(fù)原尺寸需要的時(shí)間延遲。在這個(gè)區(qū)域中，金屬服從胡克定律—闡述了在加載的彈性范圍內(nèi)，應(yīng)力和應(yīng)變成比例關(guān)系（材料在卸載后，能夠完全回復(fù)它原來的尺寸）。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)卸載時(shí)，變形消失。 如圖所示為在拉伸試驗(yàn)中沿著X軸（橫軸）的應(yīng)變和沿著Y軸（縱軸）的應(yīng)力之間的關(guān)系曲線。力學(xué)特性 力學(xué)特性包括諸如拉伸，壓縮，剪切，扭轉(zhuǎn)，沖擊，疲勞和蠕變等強(qiáng)度特性。其中包括酸性或堿性，活性和耐腐蝕性。物理特性 密度或特定的重力，濕度等都屬于此范疇。 so rapidly that the load value actully drops. This is indicated by ST. Failure occurs at this point T.Then percentage elongation and reduction in area indicate the ductility or plasticity of the material:Where and are the original and the final length of the specimen。2. the diminishing[di39。zibit]n. 展覽品；證據(jù)；展示會(huì)vt. 展覽；顯示；提出（證據(jù)等）vi. 展出；開展覽會(huì) clear ranges of elasticity, copper, zinc（鋅）, tin（錫）, etc, are found to be imperfectly[im39。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。lin?ti] n. 堿度；堿性, reactivity化學(xué)反應(yīng)的活性 and corrosion. The most important of these is corrosion which can be explained in layman’s terms as the resistance of the material to decay腐朽，腐爛 while in continuous use in a particular atmosphere.Mechanical propertiesMechanical properties include the strength properties like tensile, pression, shear, torsion, impact, fatigue and creepn. 爬行；毛骨悚然的感覺；諂媚者vi. 爬行；蔓延；慢慢地移動(dòng)；起雞皮疙瘩creep:蠕變|潛變|漸變creep strength:蠕變強(qiáng)度|潛變強(qiáng)度|蠕變?nèi)醵萩reep strain:蠕變變形|蠕動(dòng)應(yīng)變|蠕變應(yīng)變. The tensile strength of a material is obtained by dividing the maximum load, which the specimen bears by the area of crosssection of the specimen.This is a curve plotted between the stress along the Yaxis(ordinate) and the strain along the Xaxis(abscissa[230。sid?ti] n. 酸度；酸性；酸過多；胃酸過多 or alkalinity[,230。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(shí)，加熱不當(dāng)，表面易生裂紋，高溫軋制時(shí)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(shí)，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。這些鋼在空冷時(shí)間淬火，要防止冷裂。6 Mo 鉬的熔點(diǎn)高，能降低鋼的過熱傾向它和Ni一樣，使硫化物以網(wǎng)狀分布在晶界。高鉻鋼在空氣中冷卻即能淬火，常在表面生裂，所以不易鍛造。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。珠光體Ni鋼在鍛造時(shí)易形成片狀破裂和帶狀組織。3 Ni 煉鋼時(shí)有Ni極易吸收氫形成大量氣泡，鍛造時(shí)引起開裂。錳對(duì)鋼的過熱性（粗晶）很敏感，鋼錠加熱溫度過高，易生粗晶，使鍛造困難。2Mn 在鋼中形成MnS以代替FeS。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(shí)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(duì)鋼的可鍛性影響最大。它包括在熱態(tài) 或 冷態(tài)下能夠進(jìn)行錘鍛，軋制，拉伸，擠壓等加工?？慑懶?forgeability)金屬具有熱塑性，在加熱狀態(tài)(各種金屬要求溫度不同)，可以進(jìn)行壓力加工，稱為具有可鍛性?！　?鋼的原始組織的粗細(xì)和分布對(duì)奧氏體的成分將有重大影響。但晶粒粗大將增大鋼的變形