外文翻譯--普通碳鋼的淬火

1、<p><b>　　翻 譯 文 獻(xiàn)</b></p><p><b>　　原文：</b></p><p>　　HARDDENING OF PLAIN CARBON STEELS </p><p>　　Heat treatment is used to soften metal and relieve interna

2、l stresses (annealing), harden metal, and temper metal (to toughen certain parts). </p><p>　　Hardening is a process of heating and cooling steel to increase its hardness and tensile strength , to reduce its

3、ductility and to obtain a fine grain strength.</p><p>　　Hardening increases the strength of pieces after they are temperature. It is accomplishd by heating the steel to some in air, oil, water, or brine. Onl

4、y medium, high, and very high carbon steels can be hardened by this method. The temperature at which the steel must be heated varies with the steel used.</p><p>　　The tendency of a steel to harden may or may

5、 not be desirable depending upon how it is going to be processed. For example, if it is to be welded, a strong tendency to harden will make a steel brittle and susceptible to cracking during the welding process. Special

6、precautions such as preheating and a very careful control of heat input and cooling will be necessary to minimize this condition. During welding, an extremely high localized temperature differential exists between the mo

7、lten metal of th</p><p>　　The phase changes in plain carbon steels as the carbon content and the temperature vary. For a pure iron, the phase change from body-centered cubic at lower temperatures to face-cen

8、tered cubic austenite occurs at 1666F. The bcc state is termed ferrite. This ferrite phase is commonly found in carbon and alloy steels and cast irons. It can be considered to be pure iron, but in plain carbon steels it

9、is actually a solution of 0.008% carbon in iron at room temperature (though iron can dissolve somew</p><p>　　But even an extra low-carbon stainless steel contains much more carbon than 0.008%, so that the ca

10、rbon in steels must be in the steel in some form other than this. The irresistible chemical attraction between most metals and carbon has been a recurrent theme in this book: virtually all the carbon in steels denum, van

11、adium, titanium, and other metals. Here we come to the heart of the matter. We can heat-treat any steel that contains sufficient carbides. Pure iron cannot be heat-treated. Carbon st</p><p>　　To heat-treat t

12、hen, we need carbides plus one other steel characteristic-a phase transformation from austenite at higher the 300-series austenitic stainless steels do not have this second characteristic, but most steels do.</p>

13、<p>　　Iron carbide, Fe3C, is called cementite. Like other carbides, it is hard, strong, and brittle, the hardest constituent in carbon steels. Cementite has a carbon content of 6.6%. At room temperature, all carbon

14、steels are mixtures of ferrite and cementite. To harden a carbon steel, the steel is first heated to just above its critical temperature into the austenite phase. It is held at this temperature long enough for cementite

15、and other carbides to dissolve in the austenite. The steel in then cool</p><p>　　The transformation from austenite to martensite does not occur at the transformation temperature between ferrite and austenite

16、. Instead, the martensite transformation occurs over a range of temperature. Austenite may begin to transform to martensite at 80 F in a low-alloy steel. As the temperature contiues to fall, more martensite is formed , u

17、ntil at room temperature the structure of the steel may be 99% martensite. With added alloy ingredients the mertensite transformation begins at a lower te</p><p>　　Martensite is hard, brittle, and nonductile

18、, so that the denger of cracking due to thermal stresses is ever present. Worse still, there is a vonlume expansion when martensite appears. The part of the steel that is merely cooling is contracting, while the fraction

19、 that is transforming is expanding. This makes the cracking possibilities even greater.</p><p>　　In carbon steels, the brittle martensitie condition is obtainable only with a very rapid cooling rate. Additio

20、ns of any alloying ingredients affect this cooling rate. The greater the proportion of these ingredients in a steel, the slower the cooling rate that will still give a martensite condition. This statement holds true whe

21、ther the alloying metals are carbideformers. Like tungsten and molybdenum or those that dissolve in ferrite, such as nickel and manganese.</p><p><b>　　翻譯：</b></p><p><b>　　普通碳鋼的

22、淬火</b></p><p>　　熱處理是使金屬變軟，消除內(nèi)應(yīng)力（退火）和使金屬淬硬及回火（使某些部分變韌）。</p><p>　　淬火是把鋼加熱然后冷卻以提高其硬度得，抗拉強(qiáng)度，降低其韌性并獲得細(xì)晶粒組織的方法。</p><p>　　在工件制好以后進(jìn)行淬火能提高其硬度淬火是把鋼加熱到再結(jié)臨界溫度以上的某個溫度然后使之在空氣中，油中，水中或鹽水中迅速冷卻

23、來完成的。只有中碳鋼，高碳鋼以及很高的碳鋼才能用這種方法來硬化。鋼加熱到的溫度因鋼種的不同而不同。</p><p>　　鋼淬硬這一特定，是不是合乎需要，取決于何種加工。例如：如果進(jìn)行焊接加工過程中，強(qiáng)烈的淬硬趨勢是使鋼容易變脆或者開裂。必須采用專門的措施把這種情況降低到最低限度，例如進(jìn)行預(yù)熱，非常小心的控制輸入熱量以及冷卻。在焊接過程中當(dāng)焊逢熔化了的金屬和被焊接的，固態(tài)的，溫度低的多的金屬存在著極大的局部溫差。涼

24、的母體金屬對焊逢金屬及其附近已經(jīng)加熱到的臨界溫度上限以上的金屬起著一種淬火劑的作用。這些區(qū)域最后產(chǎn)生的結(jié)構(gòu)是脆硬的馬氏體。鋼的可淬性越高，使鋼淬火所必須的吸熱率的劇烈程度就越低。這是高碳鋼和合金鋼焊接時必須比低碳鋼更加小心的原因之一。</p><p>　　普通碳鋼的相，隨含碳量和溫度的變化而變化。對于純鐵，其相變從較低溫度的體心立方結(jié)構(gòu)到1666°F出現(xiàn)面心立方奧氏體。體心立方狀態(tài)時叫做鐵素體。通常在碳

25、鋼，合金鋼和鑄鐵種都有這種鐵素體相?？梢园谚F素體相看成是純鐵，但是在普通碳鋼種鐵素體相實際上是在室溫下溶有0.008%的碳的鐵（雖然在溫度更高的情況下鐵所能溶解的碳還要多些）。碳原子是很小的（0.77Å），足以嵌在體心立方晶格種的鐵原子之間。</p><p>　　然而，就是超低碳不銹鋼的含碳量也大大超過0.008%，因此，鋼種的碳必然以不同于溶入鐵素體的某種其他形式存在于鋼種。關(guān)于大多數(shù)金屬和碳之間不可

26、抗拒的親和力已經(jīng)是本書種多次重復(fù)談到的問題。實際上鋼中所有的碳都與鐵.鎢.鉻.鉬.釩.鈦和其他金屬化合成這些元素的碳化物。這里談到了問題的核心。我們能對含有足量碳化物的任何一種鋼進(jìn)行熱處理。純鐵是不能熱處理的。含碳量低于0.3%左右的碳鋼所含有的碳化物都不足以進(jìn)行任何有效的熱處理。因此含碳量通常低于0.15%的300系列的不銹鋼是不能熱處理的。馬氏體不銹鋼含有足量的碳以形成足以進(jìn)行熱處理的碳化鐵和碳化鉻。不能熱處理的鐵素體不銹鋼將在以后

27、討論。</p><p>　　因此為了進(jìn)行熱處理，我們需要碳化物再加上鋼的另一種特性―即從較高溫度下的奧氏體轉(zhuǎn)變到較低溫度下的其他相的相變。而300系列的奧氏體不銹鋼不具備這第二種特性，但大多數(shù)鋼都具備這種特性。</p><p>　　碳化鐵Fe3C叫做 。同其他的碳化物一樣，它的硬度.強(qiáng)度和脆性都很高，是碳鋼種最硬的成分。滲碳體的含碳量為6.6%。在室溫下，所有的碳鋼都是鐵素體和滲碳體的混合

28、物。要對碳鋼淬火，首先要把鋼加熱到正好超過其臨界溫度進(jìn)入奧氏體相區(qū)。把鋼在這以溫度下保溫，其保溫時間要足以使?jié)B碳體和其他碳化物溶解到奧氏體種。然后把鋼急速冷卻。這種急速冷卻是通過把之熱的鋼淬入水中或油中來實現(xiàn)的。或者，如果是焊縫的化，冷卻速度是很快的。因為迅速冷卻，奧氏體來不及分解成一般的鐵素體和滲碳體。由于急速冷卻出現(xiàn)的是碳聚集在體心正方（即四方）晶體結(jié)構(gòu)中的過飽和固溶體，這中冷凝下來的固溶體稱之為馬氏體。</p>&l

29、t;p>　　在鐵素體和奧氏體之間的轉(zhuǎn)變溫度不會發(fā)生奧氏體到馬氏體的轉(zhuǎn)變。而馬氏體轉(zhuǎn)變是在一個溫度范圍內(nèi)發(fā)生的。在低合金鋼中，奧氏體在800°F開始轉(zhuǎn)變?yōu)轳R氏體。隨著溫度繼續(xù)下降，所形成的馬氏體越多，直到在室溫時，鋼的組織中的馬時體可達(dá)99%。如果加入合金成分，馬氏體可能不會開始出現(xiàn)，在達(dá)到室溫時，也許只有80%的奧氏體發(fā)生轉(zhuǎn)變，未轉(zhuǎn)變的部分仍然是奧氏體。所有這些變化只有在合金鋼或含碳量0.3%或更多的碳鋼快速淬火的時候才

30、會發(fā)生。</p><p>　　馬氏體很硬很脆，并且是無塑性的，因此由于熱英里就有出現(xiàn)裂紋的危險。更糟的是，當(dāng)馬氏體出現(xiàn)時體積就會發(fā)生膨脹，鋼正在冷卻的部分發(fā)生收縮，而正在轉(zhuǎn)變的部分發(fā)生膨脹。這就使出現(xiàn)裂紋的可能性變的更大。</p><p>　　在碳鋼中，只有在冷卻速度非?？斓那闆r下才能獲得脆性馬氏體狀態(tài)。加入任何合金成分都會影響這個冷卻速度。鋼中合金成分的比例越大，使之出現(xiàn)馬氏體狀態(tài)的冷卻