2DS(Y)105型電動往復(fù)泵設(shè)計含5張CAD圖,ds,電動,往復(fù)泵,設(shè)計,cad 外文資料 HEAT TREATMENT OF METALS The understanding of heat treatment is embrace by the broader study of metallurgy .Metallurgy is the physics, chemistry , and engineering related to metals from ore extraction to the final product . Heat treatment is the operation do heating and cooling a metal in its solid state to change its physical properties. According to the procedure used, steel can be hardened to resist cutting action and abrasion , or it can be softened to permit machining .With the proper heat treatment internal ductile interior . The analysis of the steel must be known because small percentages of certain elements,notably carbon , greatly affect the physical properties . Alloy steels owe their properties to the presence of one or more elements other than carbon, namely nickel, chromium , manganese , molybdenum , tungsten ,silicon , vanadium , and copper . Because of their improved physical properties they are used commercially in many ways not possible with carbon steels. The following discussion applies principally to the heat treatment of ordinary commercial steel known as plain-carbon steels .With this proves the rate of cooling is the controlling factor, produces the opposite effect . A SIMPLIFIED IRON-CARBON DAGRAM If we focus only on the materials normally known as steels, a simplified diagram is often used . Those portions of the iron-carbon diagram near the delta region and those above 2% carbon content are of little importance to the engineer and are deleted. A simplified diagram, such as the one in Fig . 2.1 focuses on the eutectoid region and is quite useful in understanding the properties and processing of steel. The key transition described in this diagram is the decomposition of single-phase austenite ()to the two-phase ferrite plus carbide structure as temperature drop . Control of this reaction ,which arises due to the drastically different carbon solubilities of austenite and ferrite , enables a wide range of properties to be achieved through heat treatment . To begin to understand these processes , consider s steel of the eutectoid composition , 0.77% carbon , being slow cooled along line in Fig .2.1 At the upper temperatures , only austenite is present , the 0.77% carbon being dissolved in solid solution with the iron . When the steel cools to 727, several changes occur simultaneously . The iron wants to change from the bcc austenite structure to the bcc ferrite Structure , but the ferrite san only contain 0.02% carbon in solid solution . The rejected carbon forms the carbon-rich cementite intermetallic with composition.In essence , the net reaction at the eutectoid is: Austenite ferrite +cementite Since this chemical separation of the carbon component occurs entirely in the solid state, the resulting structure is a fine mechanical mixture of ferrite and cementite . Speciments prepared by plolishing and etching in a weak solution lf nitric acid and alcohol reveal the lamellar structure lf alternating plates that forms on slow cooling . This structure is composed of two distinct phases, but has its own set of characteristic properties and goes by the name pearlite , because of its resemblance to mother-of-pearl at low magnification. Steels having less than the eutectoid amount of carbon(less than 0.77%)are known as hypoeutectoid steels . Consider now the transformation of such a material represented by cooling along line y-y′ in Fig .2.1.At high temperatures , the material is entrirely austenite, but upon cooling enters a region where the stable phases are ferrite and austenite . Tie-line and lever-law calculations show that low-carbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon . At 727°C (1341°F),the austenite is of eutectoid compositon(0.77%carbon)and further cooling transforms the remaining austenite to pearlite. The resulting structure is a mixture lf primary or proeutectoid ferrite (ferrite that formed above the eutectoid reaction )and regions of pearlite. Hypereutectoid steels are steels that contain greater than the eutectoid amount of carbon. When such a steel cools, as in z-z′of Fig .2.1 the process is similar to the hypoeutectoid case, except that the primary or proeutectoid phase is now cementite instead lf ferrite . As the carbon-rich phase forms, the remaining austenite decreases in carbon content, reaching the eutectoid composition at 727°C(1341°F).As before, any remaining austenite transforms to pearlite upon slow cooling through this temperature. It should be remembered that the transitions that have been described by the phase diagrams are for equilibrium conditions , which can be approximated by slow cooling , With slow heating, these transitions occur in the revertse manner . However, when alloys are cooled rapidly ,entirely different results may be obtained , because sufficient time is not provided for the normal phase reactions to occur, In such cases , the phase diagram is no longer a useful tool for engineering analysis. HARDENING Hardening is the process of heating p piece of steel to a temperature within or above its critical range and then cooling it rapidly . If the carbon content of the steel is known, the proper temperature to which the steel should be heated may be obtained by reference to the iron-iron carbide phase diagram. However, if the composition of the t steel is unknown, a little preliminary experimentation may be necessary to determine the range. A good procedure to follow is to heat-quench a number lf small specimens lf the steel at various temperatures lf the steel at various temperatures and observe the results, either by hardness testing or by microscopic examination. When then correct temperature is obtained ,there will be marked change in hardness and other properties. In any heat-treating operation the rate of heating is important. Heat flows from the exterior to the interior of steel at a definite rate. If the steel is heated too fast, the outside becomes hotter than the interior and uniform structure cannot be obtained. If a piece is irregular in shape, a slow rate is all the more essential to eliminate warping and cracking. The heavier the section, the longer must be the heating time to achieve uniform results. Even after the correct remperature has been reached, the piece should be held at that temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. The hardness obtained from a given treatment depends on the quenching rate, the carbon content , and the work size, In alloy steels the kind and amount lf alloying element influences only the harden ability (the ability lf the workpiece to be hardened to depths ) lf the steel and does not affect the hardness except in unhardened or partially hardened steels . Steel with low carbon content will not respond appreciably to hardening treatments. As the carbon content in steel increases up to around 0.60%,the possible hardness can be increased only slightly, because steels above the eutectoid point are made up entirely of pearlite and cementite in the annealed state. Pearlite responds best to heat-treating operations; any steel composed mostly of pearlite can be transformed into a hard steel . As the size of parts to be hardened increases ,the surface hardness decreases somewhat even though all other conditions have remained the same. There is a limit to the rate of heat flow through steel. No matter how cool the same . There is a limit to the rate lf heat flow through steel. No matter how cool the quenching medium many be ,if the heat inside a large piece cannot escape faster than a certain critical rate, there is a definite limit to the inside hardness. However, brine or water quenching is capable lf rapidly bringing the surface lf the quenched part to it own temperature and maintaining it at or close to this temperature. Under these circumstances there would always be some finite depth of surface hardening regardless lf size. This is not true in oil quenching , when the surface temperature may be high during the critical stages of quenching. TEMPERING Steel that has been hardened by rapid quenching is brittle and not suitable for most uses . By tempering or drawing, the hardness and brittleness may be reduced to the desired point for service conditions . As these properties are reduced there is also a decrease in tensile strength and an increase in the ductility and toughness of the steel . The operation consists lf reheating quench-hardened steel to some temperature below the critical range followed by any rate lf cooling . Although this process softens steel , it differs considerably from annealing in that the process lends itself to close control lf the physical properties and in most cases does not soften the steel to the extent that annealing would. The final structure obtained from tempering a fully hardened steel is called tempered martensite . Tempering is possible because of the instability of the martensite ,the principal constituent of hardened steel. Low-temperature draws, from 300°to 400°F(150°-205°C), do not cause much decrease in hardness and are used principally to relieve internal strains. As the tempering temperatures are increased, the breakdown of the martensite takes place at a faster rate, and at about 600°F(315°C) the change to a structure called tempered martensite is very rapid. The tempering operation may be described as one lf precipitation and agglomeration or coalescence of cementite. A substantial precipitation lf cementite begins at 600°F(315°C),which produces a decrease in hardness. Increasing the temperature causes coalescence lf the carbides with continued decrease in hardness. In the process of tempering, some consideration should be given to time as well as to temperature. Although most of the softening action occurs in the first few minutes after the temperature is reached, there is some additional reduction in hardness if the temperature is maintained for a prolonged time. Usual practice is to heat the steel to the desired temperature and hold it there only long enough to have it uniformly heated. Two special processes using interrupted quenching are a form of tempering. In both, the hardened steel is quenched in a salt bath held at a selected lower temperature before being allowed to cool. These processes, known as austempering and martempering , result in products having certain desirable physical properties. ANNEALING The primary purpose of annealing is to soften hard steel so that it may be machined or cold worked . This is usually accomplished by heating the steel to slightly above the critical temperature , holding it there until the temperature of the piece is uniform throughout, and then cooling at a slowly controlled rate so that the temperature of the surface and that of the center of the piece are approximately the same. This process is known as full annealing because it wipes out all trace of previous structure, refines the crystalline structure, and softens the metal. Annealing also relieves internal stresses previously set up in the metal. The temperature to which a given steel should be heated in annealing depends on its composition; for carbon steels it can be obtained readily from the partial iron-iron the partial iron-iron carbide equilibrium diagram. The heating rate should be consistent with the size and uniformity of sections, so that the entire part is brought up to temperature as uniformly as possible. When the annealing temperature has been reached, the steel should be held there until is uniform throughout. This usually takes about 45 min for each inch (25mm) lf thickness lf the largest section. For maximum softness and ductility the cooling rate should be very slow, such as allowing the parts to cool down with the furnace. The higher the carbon content, the slower this rate must be. NORMALIZING AND SPHEROIDIZING The process of normalizing consists of heating the steel about 50°to 100°F(10°-40°)above the upper critical range and cooling in still air to room temperature . this process is principally used with low-and medium-carbon steels as well as alloy steels to make the grain structure more uniform, to relieve internal stresses, or to achieve desired results in physical properties . Most commercial steels are normalized after being rolled or cast. Spheroidizing is the process of producing a structure in which the cementite is in a spheroidal distribution. If a steel is heated slowly to a temperature just below the critical range and held there for a prolonged machinability to the steel. This treatment is particularly useful for hypereutectoid steels that must be machined. 中文翻譯 材料的熱處理 了解材料熱處理是學(xué)習(xí)冶金技術(shù)的關(guān)鍵，冶金技術(shù)是金屬通過物理學(xué)、化學(xué)、工程學(xué)，從礦石中提取，最終成為產(chǎn)品的過程，熱處理是使固態(tài)金屬加熱的情況下改變它的物理特性的一種加熱操作（根據(jù)程度不同使用）鋼的堅硬能抵抗切割和擦傷，鋼的韌性允許它加工，適當(dāng)?shù)臒崽幚砟芟齼?nèi)應(yīng)力，顆粒減小、韌性增加，硬的表面導(dǎo)致內(nèi)部的可塑性，分析鋼時可以發(fā)現(xiàn)它有小百分比元素，特別是碳，它一般會影響它的物理性能；由于物理性能的提高，它們被用在了許多不可能碳鋼的商業(yè)上。 接下來討論的是，碳鋼的熱處理在普通商業(yè)上的應(yīng)用，冷卻速度的比率是它的控制因素，快速冷卻的結(jié)果，使結(jié)構(gòu)硬化，而很慢的冷卻使工件產(chǎn)生相反的結(jié)果。 鐵碳合金圖 如果我們研究的是普通材料的鋼，對于工程人員來講，鐵碳合金圖中的近鐵素體區(qū)和含碳量大于2% 的部分不重要，所以這兩部分被除數(shù)去掉。如圖2所示，在懂的屬性和鋼的熱處理方面，在共析混合物的地區(qū)結(jié)晶，是完全有用的，主要過渡在這張圖表顯示，敘述了單項的奧氏體的分解，隨著溫度下降，轉(zhuǎn)變?yōu)殡p向鐵素體和化合物，這是反應(yīng)的控制，使大量的屬性能夠通過熱處理來完成，其理由是奧氏體和鐵素體的溫度不同，碳的析出時間也不同。 開始分析這個過程，考慮到鋼的共析成份為0.77%的碳，如圖所示，沿x-x線逐漸冷卻，在溫度線的上方，僅有一些奧氏體存在，0.77%的碳開始分解為含碳固熔體狀態(tài)，拒絕碳形成是滲碳體的本質(zhì)成份是，在共析處的反應(yīng)式是： 奧氏體=鐵素體+滲碳體 因為碳化學(xué)成份在固態(tài)時分離，由此形成一種鐵素體和滲碳體的機械混合物，準(zhǔn)備好的工件在和緩慢冷卻時，其內(nèi)部結(jié)構(gòu)為層狀的結(jié)構(gòu)形式，這種特殊的結(jié)構(gòu)有兩部分組成，而它本身也具有一系列的特性，這種結(jié)構(gòu)稱為珠光體。 含碳量比共析鋼少的（少于0.77%）是亞共析鋼，這種材料通過冷卻時在圖2.1 表現(xiàn)形式為Y-Y線。這種材料在高溫時完全是奧氏體，但在冷卻線上卻是進(jìn)入穩(wěn)定期，這是鐵素體和奧氏體的區(qū)域低碳的鐵素體成核，并結(jié)晶，剩余的奧氏體較多，在727的時候奧氏體是共析合成并進(jìn)一步冷卻轉(zhuǎn)換成為珠光體，剩余鐵素體的結(jié)構(gòu)是珠光體的再結(jié)晶或先共析鐵素體區(qū)域的一個混合物。 比共析鋼含碳量高的是過共析鋼，這種鋼冷卻的時候，在圖z-z中所示，其熱處理與亞共析鋼類似，除此之外是滲碳體而不是鐵素體，剩余的奧氏體的含碳量在減少，在727成為共析結(jié)構(gòu)，在這個溫度下緩慢冷卻，保留下來的奧氏體轉(zhuǎn)變成珠光體。 它應(yīng)該已經(jīng)是圖中描述的轉(zhuǎn)換為近似緩慢冷卻的平衡狀態(tài)，低溫加熱時，會發(fā)生相反的變化，然而合金加熱時，可能得到完全不同的結(jié)果，因為得時間為常態(tài)相，沒有被提供反作用力，在這種情況下，從工程上分析相圖確實是一個有用的工具。 淬火 淬火是將一個工件加熱到某一個溫度或臨界范圍以上，然后快速冷卻的過程，如果知道鋼的含碳量的話，到達(dá)某一溫度可能通過鐵碳合金圖來獲得數(shù)據(jù)，然而如果要是不知道鋼的結(jié)構(gòu)的話，做一個初步試驗來決定溫度范圍也是非常必要的，在各種溫度下，用許多細(xì)小的的材料來試溫，并且通過顯微鏡觀察結(jié)果，或硬度測試，鋼在硬度和其他特性上會有標(biāo)志性的改變。 在一些熱處理中，速度也是非常重要的，熱擴散從鋼的外部到內(nèi)部具有一定的速度，如果鋼加熱過快，外部變熱會比內(nèi)部快，就不能得到預(yù)期的結(jié)構(gòu)，如果工件是不規(guī)則形狀則估算變彎和砸碎緩慢時的速度更為重要，斷面較為嚴(yán)重，必須要達(dá)到一樣的結(jié)果，加熱時間相應(yīng)較長即溫度到達(dá)要求定值后工件不應(yīng)再加熱，一段時間后使它厚截面達(dá)到一樣的溫度。 通過熱處理得到硬度，取決于淬火的速度及碳的含量和工件的尺寸，在合金中，只有合金元素的類型和數(shù)量決定。 低碳鋼不能進(jìn)行熱處理，當(dāng)碳的含量增加到0.6%時硬度也可能增加，但只會硬度少量的增加，因為共析鋼在退火是被萊氏體和珠光體完全保圍，萊氏體易被加熱，所以萊氏體組成的任何一種鋼材可以熱處理變?yōu)橛蹭摗? 當(dāng)增大零件尺寸時表面硬度的增加或減低的情況仍然一樣，無論是哪種介質(zhì)的回火，如果在工件尺寸較大的部分散不其它部分熱較慢的話，就應(yīng)該有一個明確的回火極限。然而鹽水和水淬火能夠快速帶走一部分表面溫度，而且可以維持到這個溫度結(jié)束。在這些環(huán)境中，不會管表面硬度的深度大小，當(dāng)淬火時表面溫度可能在危險的范圍內(nèi)，此時用油淬火是錯誤的。 回火 鋼被快速淬火，是易碎的，不被廣泛使用，回火使硬度和脆性狀態(tài)可以被達(dá)到所需要的點，這些性質(zhì)的減低（也有抗拉強度和延展性的減小）和被冷卻后的任何繼臨界范圍韌性增加。雖然這個過程使鋼變軟，但卻不同于退火過程，在大多數(shù)情形下借助本身物理特性的控制不使鋼變軟。在那個范圍，最后的結(jié)構(gòu)從回火獲得完全增加硬度的鋼叫回火馬氏體，因為馬氏體可能是不穩(wěn)定性的，增加硬度的鋼的主要組織成份，低溫從300-400（150-205）主要不引起硬度反面的減少和減輕內(nèi)部應(yīng)力，回火是增加溫度，此時馬氏體的結(jié)構(gòu)變化非?？?，回火操作可描述為珠氏體的析出和聚結(jié)，珠氏體的析出從600（315）使硬度降低，溫度的增加會繼續(xù)使碳化合物的結(jié)合減少。 在回火工程中，有些過程應(yīng)該考慮到時間和溫度，雖然溫度達(dá)到了，但大部分軟化處理是在前幾分鐘內(nèi)發(fā)生，在有硬度的附加還原，如果加熱溫度過長的話，平常的熱處理要使鋼被加熱的溫度一樣。使用分段淬火的三個過程是回火形成的，在兩者中，增加鋼的溫度在允許范圍之內(nèi)，在較低的溫度下，在冷卻的鹽浴中淬火，這些過程即是奧氏體回火法和馬氏體回火法，使鋼獲得我們想要的物理特性。 退火 退火的最初目的是使用于制造機器的鋼變軟，否則影響工件的剛度。通常用稍高于臨界溫度的溫度加熱，直到工件獲得均勻的溫度。然后以慢速冷卻時表面溫度與中心溫度大體一致。這個過程就是完全退火，因為它去話了先前結(jié)構(gòu)中所有痕跡細(xì)化了晶粒，而且使金屬變軟，減少了內(nèi)應(yīng)力。 在鋼的穩(wěn)定的退火工程中，被加熱的溫度決定于它的合成，因為碳使它們堅如鋼，可能性從鐵碳合金圖中獲得一部分因素，對斷面的加熱速度應(yīng)該一致，所以要使整個部分盡可能的獲得一樣的增高溫度，但退火溫度達(dá)到定值時，鋼的溫度應(yīng)該在此處被保持。其中厚度為（25mm）的最大斷面大約需加熱40分鐘，最大的柔性和延展性冷卻速度應(yīng)該非常慢。應(yīng)該允許零件一爐冷卻，含碳量越高，這個比率會越慢。 正火和球化處理 正火處理在臨界范圍以上加熱到華氏50-100（10-40），并且在室溫內(nèi)冷卻。這個過程用與低碳鋼，就如合金鋼的晶粒細(xì)化一樣，來減少內(nèi)應(yīng)力以獲得更好的物理特性。大多數(shù)的普通鋼在液壓之后被卷起。 球化處理是一個類似于球體的分布結(jié)構(gòu)中產(chǎn)生珠光體的過程。如果這種鋼在它的臨界溫度下加熱并保持一段時間，這種處理在加工過共析鋼尤為重要。