1、Professional English 北華大學機械學院wangkaibaoUnit 2 Heat treatment of Materials 材料熱處理The understanding of heat treatment is embraced by the broader study of metallurgy. Metallurgy is the physics, chemistry, and engineering related to metals from ore extraction to the final product. 對熱處理的理解包含于對冶金學較廣泛的研究。冶金

2、學是物理學、化學和涉及金屬從礦石提煉到最后產物的工程學。Embrace vt. 擁抱, 互相擁抱, 包含, 收買, 信奉 vi. 擁抱 n. 擁抱Heat treatment is the operation of 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 sof

3、tened to permit machining. 熱處理是將金屬在固態(tài)加熱和冷卻以改變其物理性能的操作。按所采用的步驟，鋼可以通過硬化來抵抗切削和磨損，也可以通過軟化來允許機加工。With the proper heat treatment internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. The analysis of the steel must be known because smal

4、l percentages of certain elements, notably carbon, greatly affect the physical properties. 使用合適的熱處理可以去除內應力、細化晶粒、增加韌性或在柔軟材料上覆蓋堅硬的表面。因為某些元素(尤其是碳)的微小百分比極大地影響物理性能，所以必須知道對鋼的分析。Alloy steel owe their properties to the presence of one or more elements other than carbon, namely nickel, chromium, manganese, m

5、olybdenum, tungsten, silicon, vanadium, and copper. Because of their improved physical properties they are used commercially in many ways not possible with carbon steels. 合金鋼的性質取決于其所含有的除碳以外的一種或多種元素，如鎳、鉻、錳、鉬、鎢、硅、釩和銅。由于合金鋼改善的物理性能，它們被大量使用在許多碳鋼不適用的地方。The following discussion applies principally to the h

6、eat treatment of ordinary commercial steels known as plain carbon steels. With this process the rate of cooling is the controlling factor, rapid cooling from above the critical range results in hard structure, whereas very slow cooling produces the opposite effect. 下列討論主要針對被稱為普通碳鋼的工業(yè)用鋼而言。熱處理時冷卻速率是控制

7、要素，從高于臨界溫度快速冷卻導致堅硬的組織結構，而緩慢冷卻則產生相反效果。A Simplified Iron-carbon Diagram簡化鐵碳狀態(tài)圖If we focus only on the materials normally known as steels, a simplified diagram is often used. 如果只把注意力集中于一般所說的鋼上，經常要用到簡化鐵碳狀態(tài)圖。Those portions of the iron-carbon diagram near the delta region and those above 2% carbon content

8、 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. 鐵碳狀態(tài)圖中靠近三角區(qū)和含碳量高于2%的那些部分對工程師而言不重要，因此將它們刪除。如圖2.1所示的簡化鐵碳狀態(tài)圖將焦點集中在共析區(qū)，這對理解鋼的性能和處理是十分有

9、用的。Eutectoid n. 化類低共熔體 adj. 類低共熔體的, 共析的Of or relating to a eutectic mixture or alloy.類低共熔合金的：熔點最低的混合物或是合金的或是與其相關的n.（名詞）A eutectic mixture or alloy.類低共熔合金：熔點最低的混合物或是合金The key transition described in this diagram is the decomposition of single-phase austenite() to the two-phase ferrite plus carbide st

10、ructure as temperature drops. 在此圖中描述的關鍵轉變是單相奧氏體() 隨著溫度下降分解成兩相鐵素體加滲碳體組織結構。Control of this reaction, which arises due to the drastically different carbon solubility of austenite and ferrite, enables a wide range of properties to be achieved through heat treatment. 控制這一由于奧氏體和鐵素體的碳溶解性完全不同而產生的反應，使得通過熱處理能

11、獲得很大范圍的特性。Austenite n. 冶體A nonmagnetic solid solution of ferric carbide or carbon in iron, used in making corrosion-resistant steel.奧氏體：一種非磁性的固狀可溶性含鐵碳化物或含碳鐵，用于制作不銹鋼After Sir William Chandler Roberts- Austen (1843-1902), British metallurgist 源自威廉查德勒羅伯特- 奧斯汀 （1843-1902年）爵士，英國冶金學家 To begin to understan

12、d these processes, consider a steel of the eutectoid composition, 0.77% carbon, being slow cooled along line x-x 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(1341 ), several changes occ

13、ur simultaneously. 為了理解這些過程，考慮含碳量為0.77%的共析鋼，沿著圖2.1的x-x線慢慢冷卻。在較高溫度時，只存在奧氏體，0.77%的碳溶解在鐵里形成固溶體。當鋼冷卻到727 (1341 )時，將同時發(fā)生若干變化。The iron wants to change from the FCC austenite structure to the BCC ferrite structure, but the ferrite can only contain 0.02% carbon in solid solution. 鐵需要從面心立方體奧氏體結構轉變?yōu)轶w心立方體鐵素體結構

14、，但是鐵素體只能容納固溶體狀態(tài)的0.02%的碳。The rejected carbon forms the carbon-rich cementite intermetallic with composition Fe3C. In essence, the net reaction at the eutectoid is austenite 0.77%Cferrite 0.02%C+cementite 6.67%C. 被析出的碳與金屬化合物Fe3C形成富碳的滲碳體。本質上，共析體的基本反應是奧氏體0.77%的碳鐵素體0.02%的碳+滲碳體6.67%的碳。Since this chemical

15、separation of the carbon component occurs entirely in the solid state, the resulting structure is a fine mechanical mixture of ferrite and cementite. Specimens prepared by polishing and etching in a weak solution of nitric acid and alcohol reveal the lamellar structure of alternating plates that for

16、ms on slow cooling. 由于這種碳成分的化學分離完全發(fā)生在固態(tài)中，產生的組織結構是一種細致的鐵素體與滲碳體的機械混合物。通過打磨并在弱硝酸酒精溶液中蝕刻制備的樣本顯示出由緩慢冷卻形成的交互層狀的薄片結構。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 magn

17、ification. 這種結構由兩種截然不同的狀態(tài)組成，但它本身具有一系列特性，且因與低倍數放大時的珠母層有類同之處而被稱為珠光體。Pearlite n. 珠光體A mixture of ferrite and cementite forming distinct layers or bands in slowly cooled carbon steels.珠光體鐵：在慢慢冷卻的碳合金中的層狀鐵素體和碳素體的混合物Steels having less than the eutectoid amount of carbon (less than 0.77%) are known as hypo-

18、eutectoid steels. Consider now the transformation of such a material represented by cooling along line y-y in Fig.2.1. 含碳量少于共析體(低于0.77%)的鋼稱為亞共析鋼?，F(xiàn)在來看這種材料沿著圖2.1中y-y 線冷卻的轉變情況。At high temperatures, the material is entirely austenite, but upon cooling enters a region where the stable phases are ferrite

19、and austenite. Tie-line and level-law calculations show that low-carbon ferrite nucleates and grows, leaving the remaining austenite richer in carbon. 在較高溫度時，這種材料全部是奧氏體，但隨著冷卻就進入到鐵素體和奧氏體穩(wěn)定狀態(tài)的區(qū)域。由截線及杠桿定律分析可知，低碳鐵素體成核并長大，剩下含碳量高的奧氏體。Nucleate v. (使)成核 adj. 有核的At 727(1341 ), the austenite is of eutectoid c

20、omposition (0.77% carbon) and further cooling transforms the remaining austenite to pearlite. The resulting structure is a mixture of primary or pro-eutectoid ferrite (ferrite that formed above the eutectoid reaction) and regions of pearlite. 在727(1341 )時，奧氏體為共析組成(含碳量0.77%)，再冷卻剩余的奧氏體就轉化為珠光體。作為結果的組織結

21、構是初步的共析鐵素體(在共析反應前的鐵素體)和部分珠光體的混合物。Hypereutectoid steels are steels that contain greater than the eutectoid amount of carbon. When such steel cools, as shown in z-z of Fig.2.1 the process is similar to the hypo-eutectoid case, except that the primary or pro-eutectoid phase is now cementite instead of

22、ferrite. 過共析鋼是含碳量大于共析量的鋼。當這種鋼冷卻時，就像圖2.1的z-z線所示，除了初步的共析狀態(tài)用滲碳體取代鐵素體外，其余類似亞共析鋼的情況。As the carbon-rich phase forms, the remaining austenite decreases in carbon content, reaching the eutectoid composition at 727(1341 ). As before, any remaining austenite transforms to pearlite upon slow cooling through th

23、is temperature. 隨著富碳部分的形成，剩余奧氏體含碳量減少，在727(1341 )時達到共析組織。就像以前說的一樣，當緩慢冷卻到這溫度時所有剩余奧氏體轉化為珠光體。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 i

24、n the reverse manner. 應該記住由狀態(tài)圖描述的這種轉化只適合于通過緩慢冷卻的近似平衡條件。如果緩慢加熱，則以相反的方式發(fā)生這種轉化。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 too

25、l for engineering analysis. 然而，當快速冷卻合金時，可能得到完全不同的結果。因為沒有足夠的時間讓正常的狀態(tài)反應發(fā)生，在這種情況下對工程分析而言狀態(tài)圖不再是有用的工具。Hardening 淬火Hardening is the process of heating a piece of steel to a temperature within or above its critical range and then cooling it rapidly. 淬火就是把鋼件加熱到或超過它的臨界溫度范圍，然后使其快速冷卻的過程。If the carbon content o

26、f 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 steel is unknown, a little preliminary experimentation may be necessary to determine the range. 如果鋼的含碳量已知，鋼件合適的加熱溫度

27、可參考鐵碳合金狀態(tài)圖得到。然而當鋼的成分不知道時，則需做一些預備試驗來確定其溫度范圍。 A good procedure to follow is to heat-quench a number of small specimens of the steel at various temperatures and observe the result, either by hardness testing or by microscopic examination. When the correct temperature is obtained, there will be a marked

28、 change in hardness and other properties. 要遵循的合適步驟是將這種鋼的一些小試件加熱到不同的溫度后淬火，再通過硬度試驗或顯微鏡檢查觀測結果。一旦獲得正確的溫度，硬度和其它性能都將有明顯的變化。 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 outsid

29、e becomes hotter than the interior and uniform structure cannot be obtained. 在任何熱處理作業(yè)中，加熱的速率都是重要的。熱量以一定的速率從鋼的外部傳導到內部。如果鋼被加熱得太快，其外部比內部熱就不能得到均勻的組織結構?？梢姽馐且欢l率范圍內的電磁波。在可見光中，紅光波長最長，紫光波長最短，而這兩種光中，頻率大的是 紫 光。在真空中，黃光的傳播速度 等于 綠光的傳播速。 真空中所有電磁波的速度都一樣！ 波長乘以頻率等于光速，所以，波長越長，頻率越小。If a piece is irregular in shape, a

30、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. 如果工件形狀不規(guī)則，為了消除翹曲和開裂最根本的是加熱速率要緩慢。截面越厚，加熱的時間就要越長才能達到均勻的結果。Even after the correct temperature has been reached, the piece should be held at tha

31、t temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. 即使加熱到正確的溫度后，工件也應在此溫度下保持足夠時間以讓其最厚截面達到相同溫度。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 amoun

32、t of alloying element influences only the hardenability (the ability of the workpiece to be hardened to depths) of the steel and does not affect the hardness except in unhardened or partially hardened steels. 通過給定的熱處理所得到的硬度取決于淬火速率、含碳量和工件尺寸。除了非淬硬鋼或部分淬硬鋼外，合金鋼中合金元素的種類及含量僅影響鋼的淬透性(工件被硬化到深層的能力)而不影響硬度。Stee

33、l with low carbon content will not respond appreciably to hardening treatment. As the carbon content in steel increases up to around 0.60%, the possible hardness obtainable also increases. 含碳量低的鋼對淬火處理沒有明顯的反應。隨著鋼的含碳量增加到大約0.60%，可能得到的硬度也增加。 優(yōu)質碳素結構鋼:15為低碳鋼,45為中碳鋼,具體區(qū)分如下,(優(yōu)質碳素鋼、結構鋼的鋼號用二位數字表示，這二位數字即鋼中平均含碳

34、量的百分之幾，如：15表示C%為0.15%.)1低碳鋼低碳鋼 通常C%0.25%，叫低碳鋼，強度較低、塑性和可焊性較好。2.中碳鋼中碳鋼 C%在0.250.60%，叫中碳鋼，有較高的強度，但塑性和可焊性較差。3.高碳鋼高碳鋼 C%0.60%，叫高碳鋼。塑性和可焊性很差，但熱處理后會有很高的強度和硬度。Above this point the hardness can be increased only slightly, because steels above the eutectoid point are made up entirely of pearlite and cementite

35、 in the annealed state. Pearlite responds best to heat-treating operations; and steel composed mostly of pearlite can be transformed into a hard steel. 高于此點，由于超過共析點鋼完全由珠光體和退火狀態(tài)的滲碳體組成，硬度增加并不多。珠光體對熱處理作業(yè)響應最好；基本由珠光體組成的鋼能轉化成硬質鋼。As the size of parts to be hardened increases, the surface hardness decreases

36、 somewhat even though all other conditions have remained the same. There is a limit to the rate of heat flow through steel. 即使所有其它條件保持不變，隨著要淬火的零件尺寸的增加其表面硬度也會有所下降。熱量在鋼中的傳導速率是有限的。No matter how cool the quenching medium may be, if the heat inside a large piece cannot escape faster than a certain critic

37、al rate, there is a definite limit to the inside hardness. However, brine or water quenching is capable of rapidly bringing the surface of the quenched part to its own temperature and maintaining it at or close to this temperature. 無論淬火介質怎么冷，如果在大工件中的熱量不能比特定的臨界速率更快散發(fā)，那它內部硬度就會受到明確限制。然而鹽水或水淬火能夠將被淬零件的表面

38、迅速冷卻至本身溫度并將其保持或接近此溫度。Under these circumstances there would always be some finite depth of surface hardening regardless of size. This is not true in oil quenching, when the surface temperature may be high during the critical stages of quenching. 在這種情況下不管零件尺寸如何，其表面總歸有一定深度被硬化。但油淬情況就不是如此，因為油淬時在淬火臨界階段零件表

39、面的溫度可能仍然很高。Tempering 回火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 快速淬火硬化的鋼是硬而易碎的，不適合大多數場合使用。通過回火，硬度和脆性可以降低到使用條件所需要的程度。As these properties a

40、re reduced there is also a decrease in tensile strength and an increase in the ductility and toughness of the steel. The operation consists of reheating quench-hardened steel to some temperature below the critical range followed by any rate of cooling. 隨著這些性能的降低，拉伸強度也降低而鋼的延展性和韌性則會提高?；鼗鹱鳂I(yè)包括將淬硬鋼重新加熱到低

41、于臨界范圍的某一溫度然后以任意速率冷卻。Although this process softens steel, it differs considerably from annealing in that the process lends itself to close control of 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 f

42、ully hardened steel is called tempered martensite. 雖然這過程使鋼軟化，但它與退火是大不相同的，因為回火適合于嚴格控制物理性能并在大多數情況下不會把鋼軟化到退火那種程度。回火完全淬硬鋼得到的最終組織結構被稱為回火馬氏體。Tempering is possible because of the instability of the martensite, the principal constituent of hardened steel. Low-temperature draws, from 300 to 400 (150205), do

43、not cause much decrease in hardness and are used principally to relieve internal strains. 由于馬氏體這一淬硬鋼主要成分的不穩(wěn)定性，使得回火成為可能。低溫回火， 300 到400 (150205)，不會引起硬度下降很多，主要用于減少內部應變。 As the tempering temperatures are increased, the breakdown of the martensite takes place at a faster rate, and at about 600 (315) the

44、change to a structure called tempered martensite is very rapid. The tempering operation may be described as one of precipitation and agglomeration or coalescence of cementite. 隨著回火溫度的提高，馬氏體以較快的速率分解，并在大約600 (315)迅速轉變?yōu)楸环Q為回火馬氏體的結構?；鼗鹱鳂I(yè)可以描述為滲碳體析出和凝聚或聚結的過程。 A substantial precipitation of cementite begins

45、 at 600 (315), which produces a decrease in hardness. Increasing the temperature causes coalescence of the carbides with continued decrease in hardness. 滲碳體的大量析出開始于600 (315)，這使硬度下降。溫度的上升會使碳化物聚結而硬度繼續(xù)降低。In the process of tempering, some consideration should be given to time as well as to temperature.

46、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. 在回火過程中，不但要考慮溫度而且要考慮時間。雖然大多數軟化作用發(fā)生在達到所需溫度后的最初幾分鐘，但如果此溫度維持一段延長時間，仍會有些額外的硬度下降。Usual practice is t

47、o heat the steel to the desired temperature and hold it there only long enough to have it uniformly heated. 通常的做法是將鋼加熱到所需溫度并且僅保溫到正好使其均勻受熱。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 tempera

48、ture before being allowed to cool. These processes, known as austempering and martempering, result in products having certain desirable physical properties. 兩種采用中斷淬火的特殊工藝也是回火的形式。這兩種工藝中，淬硬鋼在其被允許冷卻前先在一選定的較低溫度鹽浴淬火。這兩種分別被稱為奧氏體回火和馬氏體回火的工藝，能使產品具有特定所需的物理性能。 Annealing 退火The primary purpose of annealing is t

49、o soften hard steel so that it may be machined or cold worked. 退火的主要目的是使堅硬的鋼軟化以便機加工或冷作。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

50、 so that the temperature of the surface and that of the center of the piece are approximately the same. 通常是非常緩慢地將鋼加熱到臨界溫度以上，并將其在此溫度下保持到工件全部均勻受熱，然后以受控的速率慢慢地冷卻，這樣使得工件表面和內部的溫度近似相同。This process is known as full annealing because it wipes out all trace of previous structure, refines the crystalline struc

51、ture, and softens the metal. Annealing also relieves internal stresses previously set up in the metal. 這過程被稱為完全退火，因為它去除了以前組織結構的所有痕跡、細化晶粒并軟化金屬。退火也釋放了先前在金屬中的內應力。The temperature to which a given steel should be heated in annealing depends on its composition; for carbon steels it can be obtained readily

52、 from the partial iron-iron carbide equilibrium diagram. When the annealing temperature has been reached, the steel should be held there until it is uniform throughout. 給定的鋼其退火溫度取決于它的成分；對碳鋼而言可容易地從局部的鐵碳合金平衡圖得到。達到退火溫度后，鋼應當保持在此溫度等到全部均勻受熱。This usually takes about 45min for each inch(25mm) of thickness o

53、f 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. 加熱時間一般以工件的最大截面厚度計每英寸(25mm )大約需45min。為了得到最大柔軟性和延展性冷卻速率應該很慢，比如讓零件與爐子一起冷下來。含碳量越高，冷卻的速率必須

54、越慢。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. 加熱的速率也應與截面的尺寸及均勻程度相協(xié)調，這樣才能使整個零件盡可能均勻地加熱。Rimming steel Rimmed steel 沸騰鋼Normalizing and Spheroidizing正火和球化The process of normalizing consist

55、s of heating the steel about 50 to 100 (1040) above the upper critical range and cooling in still air to room temperature. 正火處理包括先將鋼加熱到高于上臨界區(qū)50到100 (1040)然后在靜止的空氣中冷卻到室溫。This process is principally used with low- and medium-carbon steels as well as alloy steels to make the grain structure more unifor

56、m, to relieve internal stresses, or to achieve desired results in physical properties. Most commercial steels are normalized after being rolled or cast. 正火主要用于低碳鋼、中碳鋼及合金鋼，使晶粒結構更均勻、釋放內應力或獲得所需的物理特性。大多數商業(yè)鋼材在軋制或鑄造后都要正火。Spheroidizing is the process of producing a structure in which the cementite is in a

57、spheroidal distribution. If steel is heated slowly to a temperature just below the critical range and held there for a prolonged period of time, this structure will be obtained. 球化是使?jié)B碳體產生成類似球狀分布結構的工藝。如果把鋼緩慢加熱到恰好低于臨界溫度并且保持較長一段時間，就能得到這種組織結構。The globular structure obtained gives improved machinability

58、to the steel. This treatment is particularly useful for hypereutectoid steels that must be machined. 所獲得的球狀結構改善了鋼的可切削性。此處理方法對必須機加工的過共析鋼特別有用。eutectoid steel 具有共析成分含0.77%碳的碳素鋼。該鋼由高溫奧氏體區(qū)緩冷至723，生成多邊形珠光體組織，其中鐵素體和滲碳體呈片狀平行排列。優(yōu)質碳素結構鋼和碳素工具鋼都包含有這種組織。什么叫共析鋼？什么叫共析鋼？ 碳溶解在鐵的晶格中形成固溶體，碳溶解到鐵中的固溶體叫鐵素體，溶解到鐵中的固溶體叫奧氏體。鐵

59、素體與奧氏體都具有良好的塑性。當鐵碳合金中的碳不能全部溶入鐵素體或奧氏體中時，剩余出來的碳將與鐵形成化合物碳化鐵（Fe3C）這種化合物的晶體組織叫滲碳體，它的硬度極高，塑性幾乎為零。從反映鋼的組織結構與鋼的含碳量和鋼的溫度之間關系的鐵碳平衡狀態(tài)圖上可見，當碳的含量正好等于0.77%時，即相當于合金中滲碳體（碳化鐵）約占12%，鐵素體約占88%時，該合金的相變是在恒溫下實現(xiàn)的。即在這種特定比例下的滲碳體和鐵素體，在發(fā)生相變時，如果消失兩者同時消失（加熱時），如果出現(xiàn)則兩者又同時出現(xiàn)，在這一點上這種組織與純金屬的相變類似?；谶@個原因，人們就把這種由特定比例構成的兩相組織當作一種組織來看待，并且命

60、名為珠光體，這種鋼就叫做共析鋼。即含碳量正好是0.77%的鋼就叫做共析鋼，它的組織是珠光體。Surface Hardening表面硬化CarburizingThe oldest known method of producing a hard surface on steel is case hardening or carburizing. Iron at temperatures close to and above its critical temperature has an affinity for carbon.滲碳 最早的硬化鋼表面的方法是表面淬火或滲碳。鐵在靠近并高于其臨界溫度