钢铁热处理中英文对照外文翻译文献

中英文对照外文翻译
(文档含英文原文和中文翻译)
原文:
Heat Treatment of Steel
Types of Heat Treating Operations Five Operations are detailed in this lesson as the basis of heat treatment. Explanations of these operations follow.
Full annealing Full annealing is the process of softening steel by a heating and cooling cycle, so that it may be bent or cut easily. In annealing, steel is heated above a transformation temperature and cooled very slowly after it has reached a suitable temperature. The distinguishing characteristics of full annealing are: (a) temperature above
the critical temperature and (b) very slow cooling, usually in the furnace.
Normalizing Normalizing is identical with annealing, except that the steel is air cooled; this is much faster than cooling in a furnace. Steel is normalized to refine grain size, make its structure more uniform, or to improve machinability.
Hardening Hardening is carried out y quenching a steel, that is, cooling it rapidly from a temperature above the transformation temperature. Steel is quenched in water or brine for the most rapid cooling, in oil for some alloy steels, and in air for certain higher alloy steels. After steel is quenched, it is usually very hard and brittle; it may even crack if dropped. To make the steel more ductile, it must be tempered.
Tempering Tempering consistes of reheating a quenched steel to a suitable temperature below the transformation temperature for an appropriate time and cooling back to room temperature. How this process makes steel tough will be discussed later.
Stress relieving Stress relieving is the heating of steel to a temperature below the transformation temperature, as in tempering, but is done primarily to relieve internal stress and thus prevent distortion or cracking during machining.
This is sometimes called process annealing.
Reasons for Heat Treating Heat treatment of steel is usually intended to accomplish any one of the following objectives:
●Remove stresses induced by cold working or to
remove stresses set up by nonuniform cooling of hot metal
objects;
●Refine the grain structure of hot worked steels
which may have developed coarse grain size;
●Secure the proper grain structure;
●Decrease the hardness and increase the ductility;
●Increase the hardness so as to increase resistance
to wear or to enable the steel to withstand more service
conditions;
●Increase the toughness; that is, to produce a steel
having both a high tensile strength and good ductility,
enabling it to withstand high impact;
●Improve the machinability;
●Improve the electrical properties;
●Change or modify the magnetic properties of steel.
Heat Treatment The hardest condition for any givens steel is obtained by quenching to a fully martensitic structure.
Since hardness is directly related to strength, a steel composed of 100% martensite is at its strongest possible condition. However, strength is not the only property that must be considered in the application of steel parts. Ductility may be equally important.
Tempering Ductility is the ability of a metal to change shape before it breaks. Fleshly quenched martensite is hard but not ductile; in fact, it is very brittle. Tempering is needed to impart ductility to the martensite, usually at a smell sacrifice in strength. In addition, tempering greatly increases the resistance of martensite to shock loading.
The effect of tempering may be illustrated as follows. If the head of a hammer were quenched to a fully martensitic structure, it probably would crack after the first few blows. Tempering during manufacture of the hammer imparts shock resistance with only a slight decrease in hardness. Tempering is accomplished by heating a quenched pert to some point below the transformation temperature, and holding it at this temperature for an hour or more, depending on its size. Most steels are tempered between 205 and 5,950C. As higher temperatures are employed, toughness or shock resistance of the steel is increased, but the hardness and strength decrease.
Annealing the two-stage heat treating process of quenching and tempering is designed to produce high strength steel capable of resisting shock and deformation without breaking. On the other hand, the annealing process is intend to make steel easier to deform of machine. In manufacturing steel products, machining and severe bending operations are often employed. Even tempered steel may not cut or bend very easily and annealing is often necessary.
Process annealing Process annealing consists of heating steel to a temperature just below the lowest transformation temperature for a short time. This makes the steel easier to form. This heat treatment is commonly applied in the sheet and wire industries, and the temperatures generally used are from 550 to 650o C.
Full annealing Process annealing, where steel is heated 50 to 100 o C above the third transformation temperature for hypoeutectoid steels, and above the lowest transformation temperature for hypereutectoid steels, and slow cooled, makes the steel much easier to cut, as well as bend. In full annealing, cooling must take place very slowly so that a coarse pearlite is formed. Show cooling is not essential for process annealing, since any cooling rate from temperatures below the lowest
transformation temperature will result in the same microstructure and hardness.
During cold deformation, steel has a tendency to harden in deformed areas, making it more difficult to bend and liable to breakage. Alternate deforming and annealing operations are performed on most manufactured steel products.
Normalizing The process of normalizing consists of heating to a temperature above the third transformation temperature and allowing the pert to cool in still air. The actual temperature required for this depends on the composition of the steel, but is usually around 870o C. Actually, the term normalize does not describe the purpose. The process might be more accurately described as a homogenizing or grain-refining treatment. Within any piece of steel, the composition is usually not uniform throughout. That is, one area may have more carbon than the area adjacent to it. These compositional differences affect the way in which the steel will respond t heat treatment. If it is heated to a high temperature, the carbon can readily diffuse throughout, and the result is a reasonably uniform composition from one area to next. The steel is then more homogeneous and will respond to the heat treatment in a more uniform way.
Because of characteristics inherent in cast steel, the normalizing treatment is more frequently applied to ingots prior to working, and to steel castings and forgings prior to hardening.
Stress Relieving When a metal is heated, expansion occurs which is more or less proportional to the temperature rise. Upon cooling metal, the reverse reaction takes place. That is, a contraction is observed. When a steel bar or plate is heated at one point more than at another, as in welding or during forging, internal stress are set up. During heating, expansion of the heated area cannot take place unhindered, and it tends to deform. On cooling, contraction is prevented from taking place by the unyielding cold metal surrounding the heated area. The forces attempting to contract the metal are not relieved, and when the metal is cold again, the forces remain as internal stresses. Stresses also result from volume changes, which accompany metal transformations and precipitation. Internal or residual stresses are bad because they may cause warping of steel parts when they are machined. To relieve these stresses, steel is heated to around 595o C, assuming that the entire pert is heated uniformly, then cooled slowly back to room temperature. This procedure is called
stress relief annealing, or merely stress relieving.
译文：
钢的热处理
各种类型的热处理本单元详细介绍了五种热处理的基本方法。

这些方法如下。

完全退火完全退火是利用冷热循环使钢铁硬度下降的过程，之后它就容易被切割和弯曲。

在退火时，钢被加热到相变温度上并且达到一个合适温度后就缓慢冷却。

完全退火的区别其他退火的特点是：（a）温度高于临界温度（b）缓慢冷却，通常是炉冷。

正火正火与退火相同，除了钢铁的正火是空冷，这样将比在炉中冷却的快。

金属进行正火是为了细化精粒，使它的组织更加规律，或提高它的机械加工性能。

淬火淬火就是钢淬火，它是将钢从临界温度以上迅速冷却。

钢一般是在水中或者卤水中进行淬火，这是为了快速冷却，而另外一些合金钢用油冷，以及某些高等合金钢要用空冷。

钢催后之后，一般会很硬很脆，有可能在落地后碎裂。

为了是钢有更高的韧性它，必须还要经过回火
回火回火是将淬火过的钢再次加热到转变温度以下一定时间后再冷却到室温的热处理工艺。

这个过程是如何使钢有高硬度之后将会讨论。

去应力去应力是加热钢到转变温度一下，如同回火一样，但
这样做主要是为了消除内应力和防止在机械加工的过程中的扭曲和变形。

有时候我们也称这个过程叫做退火。

热处理的原因钢的热处理经常是为了完善如下几个方面：
消除在冷却过程中产生的应力和消除热金属处理中的应力。

细化晶粒组织，钢可能在热加工过后会产生粗大的晶粒。

获得稳定的适当的晶粒结构
降低硬度，提高塑性。

增加硬度以提高抗磨损能力或者使金属能够承受更多条件环境。

、
增加韧性，这样一来，可以使钢同时拥有高拉伸性和好的延展性，使它能承受高程度的碰撞。

提高切削性能。

提高导电性。

改变钢的磁性。

热处理对于任何一种钢而言，最困难的是获得马氏体。

由于硬度和强度有直接关系，钢由百分之百的马氏体组成时它处于最大强度状态。

然而，强度并不是钢在应用中唯一考虑的性质，延展性同样重要。

回火可塑性是指金属在其破裂前改变形状的能力。

马氏体本身具有很高硬度但延展性不高，而且易碎。

回火是被用作使马氏体具有良好的可塑性，往往是牺牲了一小部分的强度。

此外，回火处理大大增加了马氏体抵抗冲击负荷的能力。

回火的影响以下举例说明。

如果一个锤子的头经过淬火变成完全马氏体的结构，它很可能在最初的几次打击后破裂。

锤子的韧性在回火过程中获得提高而仅仅伴随硬度稍微降低。

回火是经过淬火后急速冷却到相变温度下某一点的过程，并且保持这个温度一个小时或者更久，这个温度由钢的尺寸来决定。

大多数钢的回火温度在205℃~595℃。

随着温度的提高，钢的韧性和抗冲击强度也增强，但是硬度和强度下降。

退火在回火和淬火这两个工艺阶段，其目的是能制造可以抵抗高冲击强度和磨损变形的高强度钢材。

令一方面，退火工艺的目的是使得钢材容易加工和变形。

在钢制品的机械加工中，机械制造产生的弯曲是非常常见的。

经过回火的钢材可能不容易被切割和弯曲，所以回火往往是必要的。

退火工艺退火工艺需要加热钢材到最低相变温度下一段时间。

这使钢更容易成型。

这种热处理往往被用于钢铁和电线产业，其工艺温度一般在550~650℃。

完全退火完全退火，就是把钢材加热到第三转变温度以上50~100℃使之成为亚共析钢，或者加热到最低转变温度以上为过共析钢，经过缓慢冷却，使钢材容易被切削和弯曲。

在完全退火中，冷却必须进行的很缓慢从而使之形成粗糙的珠光体。

缓慢冷却并不是退火过程中必不可少的，这是由于加热到最低的转变温度以下后，任何冷却速度都会导致钢材形成同样的结构和硬度。

在冷变形中，钢材有着在形变区域内变硬的趋势，使之更难弯曲
和容易被损坏。

在大多数的机械加工钢材中，交替变形和退火都被使用缺一不可。

正火正火过程包括把钢材加热到第三温度以上并使其在空气中冷却。

正火实际需要的温度取决于钢的组成成分，但通常在870℃左右。

实际上，这个过程并不能描述其目的。

把这个过程描述为均匀或晶粒细化处理可能会更准确些。

做一小块钢材上，它的组成通常是不一样的。

也就是说，某一个区域上会比它的领域含有更多的碳。

这些成分的差异影响着钢的热处理。

如果加热到一个较高的温度，碳很可能迅速扩散到各处，结果就是每一区域的碳都是均匀的。

这时的钢材比较匀质并且更易于热处理。

由于铸铁的固有性质，被加工前的铸铁块往往更需要频繁的正火加工，然后才是进行浇铸和变硬。

去应力当金属被加热时，它就会产生膨胀，膨胀的多少与加工温度成比例关系。

如果降温，金属就会发生相反的反应。

即注意到钢材的缩小。

当钢的某一点加热的温度高于其它地方时，就像焊接或锻造一样，那一点就会产生内应力，。

加热过程中，膨胀的区域不能被诛之，并且它会趋向于变形。

冷却时，高温区域的缩小会被周围的冷区域的材料阻止。

那些使金属压缩的应力并没有减弱，当金属在次冷却时，这个力与内应力一样不变。

压力往往随着体积改变，这种变化伴随着材料的转变和析出。

内应力和残余应力都是有害的，这是因为在加工时它们可能会导致钢铁部件的变形。

为消除这些应力，钢材要加热到595℃左右，确定整个材料被加热均匀，再慢慢冷却到室温。

这种程序被称为去应力退火，或者为去应力。