【正文】 、開裂傾向和降低韌性。其次是合金元素的影響，除鈷外，絕大多數(shù)合金元素溶入奧氏體后，均使C曲線右移，降低臨界冷卻速度，從而提高鋼的淬透性。淬透性好的鋼材，可使鋼件整個(gè)截面獲得均勻一致的力學(xué)性能以及可選用鋼件淬火應(yīng)力小的淬火劑，以減少變形和開裂。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)。鋼材淬透性好與差，常用淬硬層深度來表示。淬透性：指在規(guī)定條件下，決定鋼材淬硬深度和硬度分布的特性。改變?nèi)魏我环N均會(huì)產(chǎn)生不同的切削效果。 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。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。柔軟的金屬往往會(huì)被加入合金從而犧牲它的延展性來提高加工性能。許多時(shí)候，因?yàn)椴牧线^軟而難于穩(wěn)定加工。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。s230。可加工性是刀具和零件的結(jié)合。MachinabilityMachinability（機(jī)械加工性能） means several things. To production men it generally means being able to remove metal at the fastest rate, leave the best possible finish, and obtain the longest possible tool life. Machinability applies to（應(yīng)用于） the toolwork（工具，零件） bination.可加工性可加工性意味著幾件事情。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(huì)太快，產(chǎn)生了低速冷卻的結(jié)果。預(yù)熱可以取得與之相當(dāng)?shù)男Ч?。有兩點(diǎn)值得注意：吸收熱量的多少；移除速度。 the rate at which it is removed.焊接％。經(jīng)過熱處理的工件像我們看到的那樣會(huì)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)。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(huì)引起翹曲的懷疑存在時(shí)，可以通過將工件加工至1100然后進(jìn)行冷卻來驗(yàn)證。例如工件停止成型加工后會(huì)發(fā)生回彈，在隨后的熱處理后，工件會(huì)發(fā)生翹曲。這不是一種科學(xué)的敘述方法，但確實(shí)是發(fā)生了。It is quite interesting in this connection（關(guān)于這一點(diǎn)，就此而論） to discover that deep draws can sometimes be made in one rapid operation that could not possibly be done leisurely（緩慢地，從容不迫地） in two or three. If a draw is half made and then stopped, 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(shí)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)。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。 likewise（同樣地）, the steel must have sufficient（充足的） ductility to flow to the required shape without cracking. The force required depends on the yield point, because deformation starts in the plastic range above the yield point of steel. Workhardening also occurs here, progressively（日益增多地） stiffening（使變硬） the metal and causing difficulty, particularly（獨(dú)特的，顯著的） in the lowcarbon steels.成形鋼的冷成形是它的拉伸強(qiáng)度和延展性相結(jié)合的結(jié)果。鉻在鍛造溫度下時(shí)使鋼硬化，但釩沒有明顯的效果；兩種加工方法對(duì)高碳鋼沒有影響。lb的沖擊下表現(xiàn)出與相同碳含量普通鋼幾乎同樣的塑性。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。Lowcarbon, nickelchromium(鉻) steels are just about幾乎，差不多j as plastic at high temperature under a single 520ft高碳鋼很難鍛造。 therefore, not much can be done無論做什么都是 白費(fèi)力，都改變不了既定的現(xiàn) 實(shí) to improve its forgeability. Highercarbon steel is difficult to forge. Large grain size is best if subsequent heat treatment will refine the grain size.關(guān)于加工的考慮最后零件的特性（硬度、強(qiáng)度和可加工性）而不是鍛造特性決定了材料的選擇。Considerations in fabrication(制造)The properties of the final part (hardness, strength, and machinability [m?,?i:n?39。不僅僅是因?yàn)檫@種鋼含有2％的合金元素另一種鋼含有1％而使前者具有了后者沒有的某些能力，或者是某種鋼具有神奇的名字。 this is particularly true of alloy steels.在鋼之間沒有太大的區(qū)別；所有的鋼在機(jī)械性能方面都是近似的。 , and not with the idea that “this” steel can do something no other can do because it contains 2 percent instead of 1 percent of a certain alloying element, or because it has a mysterious [mi39。bil?ti]是產(chǎn)品在被調(diào)用時(shí)能夠運(yùn)行（即未處于失效或修復(fù)狀態(tài)）的概率。 all are very similar in mechanical properties. Selection must be made on factors such as hardenability [,hɑ:d?n?39。舉例來說，它可以強(qiáng)度很高，并且有好的耐磨性；它可以被例如拉伸加工，機(jī)械加工，或焊接等特殊工藝來加工出來；它可以被循環(huán)利用；它的成本和實(shí)用性是首要的。 我們不能在這里討論這些深?yuàn)W的特性。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。在所有的金屬產(chǎn)量中，％，％，％。（主要由鐵和碳構(gòu)成的合金）它們的重量占所有生產(chǎn)出來的金屬重量的98%。 在50種左右的金屬元素里，工程實(shí)踐中只有少數(shù)金屬被大量生產(chǎn)和使用。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)。金屬這個(gè)詞可以包括工業(yè)用純金屬和它的合金。得到的物質(zhì)被叫做合金。如果是有益的，它們被認(rèn)為是合金元素。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(duì)某種特定的屬性沒有影響。 絕對(duì)純凈的金屬?gòu)膩硪矝]有被生產(chǎn)出來過。在原子范圍內(nèi)，晶粒之間相互接觸緊密結(jié)合。在工程實(shí)踐中應(yīng)用的金屬由大量的晶體組成，這些晶體稱之為晶粒。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。 從我們的觀點(diǎn)來看，在所有的特性中結(jié)晶性是最重要的。許多金屬具有延展性，也就是說，在不被破壞的情況下它們的形狀在外力的作用下可以發(fā)生變化。它們是熱和電的良導(dǎo)體，不透光。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。金屬和非金屬之間的區(qū)別不是特別明顯。 and its cost and availability may be of critical importance. 在人類社會(huì)的發(fā)展中，金屬的應(yīng)用起著關(guān)鍵性的作用。 it may have to be able to be fabricated by a particular process such as deep drawing, machining, or welding。2. Suffice it to say that the gun was his.只需說這槍是他的就夠了。teini?m, ti]n. [化]鈦（金屬元素）. Aluminum accounts for about % by weight of all metals produced, and copper about %, leaving only % for all other metals. As might be expected, the remainders are all used in rather相當(dāng) special applications. For example, nickel alloys are used principally主要地 in corrosionand heatresistant applications, while titanium is used extensively廣泛地 in the aerospace industry because its alloys have good binations of high strength and low density. Both nickel and titanium are used in highcost, highquality applications, and, indeed, it is their high cost that tends to restrict their application. We cannot discuss these more esotericadj. 秘傳的；限于圈內(nèi)人的；難懂的Esoteric Buddhism:密宗|密宗，特別是指西藏的喇嘛教。t230。Unit 1 Metals金屬 The use of metals has always been a key factor in the development of the social systems of man. Of the roughl