第6次课 UNIT 4 Forging Processes

1、w 1.Introduction of Forgingw 2.Common Forging Processes w 3.Die Design Consideration w 4.Tolerancesw Forging is an important hot-forming process. It is used in producing components of all shapes and sizes, from quite small items to large units weighing several tons.w 锻造是一种重要的热成型工艺。它能用于生锻造是一种重要的热成型工艺

2、。它能用于生产各种形状和尺寸、从很小到重量数吨的零产各种形状和尺寸、从很小到重量数吨的零件。件。1.Introduction of Forgingw Forging is the process by which metal is heated and is shaped by plastic deformation by suitably applying compressive force. Usually the compressive force is in the form of hammer blows using a power hammer or a press, as sho

3、wn in Fig.4.1.w 在锻造过程中先将金属加热，然后施加合适在锻造过程中先将金属加热，然后施加合适的压力使其的压力使其塑性变形塑性变形。通常压力都是以由如。通常压力都是以由如图图4.1所示的所示的动力锤动力锤或或压力机压力机提供的提供的锤击锤击形式形式出现。出现。1.Introduction of Forgingw Hand forging tools comprise variously shaped hammers. The base on which the work is supported during forging is the anvil(铁砧铁砧).w 手工锻造工具

4、包括各种不同形状的锤子。在手工锻造工具包括各种不同形状的锤子。在锻造中用于支撑工件的基础是锻造中用于支撑工件的基础是铁砧铁砧。1.Introduction of Forgingw For the semimechanized forging of small to medium-sized components, forging hammers powered by various means are employed. The feature common to all of them is that, like the hand forging hammer, they utilize t

5、he energy of a falling weight to develop the pressure needed for shaping the metal. w 对小到中等尺寸零件的对小到中等尺寸零件的半机械化锻造半机械化锻造而言，而言，锻锤可采用多种动力。就其一般特性而言，锻锤可采用多种动力。就其一般特性而言，都象都象手工锻锤手工锻锤一样，它们均利用落重能量来一样，它们均利用落重能量来产生金属成型所需的压力。产生金属成型所需的压力。1.Introduction of Forgingw Larger components are forged by means of (借助，用到借助

6、，用到) forging presses operated by steam or compressed air or by hydraulic or electric power. Largely automatic forging machines are used for the quantity production of engineering parts.w 锻造大零件则要用到蒸汽、压缩空气、液力锻造大零件则要用到蒸汽、压缩空气、液力或电力驱动的或电力驱动的锻压机锻压机。大型的自动化锻机用。大型的自动化锻机用于工程零件的批量生产。于工程零件的批量生产。1.Introduction

7、of Forgingw A distinction may be made between open-die(开模，冲模开模，冲模) forging, usually in the form of hammer forging, and closed-die forging. In hammer forging, the component is shaped by hammer blows aided by relatively simple tools. These may include open dies i.e., dies that do not completely enclos

8、e the metal to be shaped. w 锤锻中常用的锤锻中常用的开式模锻开式模锻与与闭式模锻闭式模锻是有区别是有区别的。在锤锻中零件通过锤击辅之以相对简单的。在锤锻中零件通过锤击辅之以相对简单的工具成型。其中包括开式锻模，就是不完的工具成型。其中包括开式锻模，就是不完全封闭被成型金属的模具。全封闭被成型金属的模具。1.Introduction of Forgingw One of the basic operations of hammer forging is the elongation of a piece of metal by stretching with hamm

9、er blows, causing it to become thinner and longer. In hand forging the work-piece is usually turned 90after each blow, in order to forge it thoroughly and prevent its lateral expansion. w 锤锻的基本操作之一就是通过锤击使金属锤锻的基本操作之一就是通过锤击使金属伸伸长长，促成其，促成其变细变长变细变长。手工锻造时一般在每。手工锻造时一般在每次锤击后都转过次锤击后都转过90以充分锻打工件并防止以充分锻打工件并防止

10、横向膨胀横向膨胀。1.Introduction of Forgingw The opposite of elongation is upsetting, which produces compressive shortening. For example, the diameter of a bar can be increased by heating and hammering axially.w 与与伸长伸长相反的是相反的是镦粗镦粗，即产生压缩性缩短。，即产生压缩性缩短。例如，例如，棒料棒料的直径可以通过加热和的直径可以通过加热和轴向轴向锤击锤击而增大。而增大。1.Introductio

11、n of Forgingw More important is closed-die forging, very widely used for mass production in industry, in which the metal is shaped by pressing between a pair of forging dies. The upper die is usually attached to the ram of a forging press or a forging hammer, while the lower die is stationary. w 更重要

12、的是更重要的是闭式模锻闭式模锻，在工业上广泛用于，在工业上广泛用于规规模生产模生产。闭式模锻中金属在一对。闭式模锻中金属在一对锻模锻模之间挤之间挤压成型。顶模通常放在锻压机的撞头或锻锤压成型。顶模通常放在锻压机的撞头或锻锤上，而底模则是上，而底模则是固定的固定的。1.Introduction of Forgingw Together they form a closed die. Closed-die forging can produce components of greater complexity and accuracy, with a better surface finish t

13、han the more traditional methods not using closed dies. The dies are made of special heat-resistant and wear-resistant tool steels.w 两者合在一起形成闭式锻模。两者合在一起形成闭式锻模。闭式模锻闭式模锻能生能生产高度复杂和精确的零件，而且表面光洁度产高度复杂和精确的零件，而且表面光洁度要比不用闭式锻模的更传统方法好。闭式锻要比不用闭式锻模的更传统方法好。闭式锻模采用特殊的耐热、耐磨工具钢制成。模采用特殊的耐热、耐磨工具钢制成。1.Introduction of F

14、orgingw A piece of hot metal sufficient to slightly overfill the die shape is placed in the bottom die, and the top die is forced against it, so that the metal takes the internal shape of the die. w 将一块大小足以充填将一块大小足以充填模腔模腔并能稍有并能稍有溢出溢出的加的加热金属放入底模，并将顶模加压合拢，这块热金属放入底模，并将顶模加压合拢，这块金属便获得该金属便获得该模腔模腔的形状。的形状。1

15、.Introduction of Forgingw Closed-die forging is used for the rapid production of large numbers of fairly small parts and also for very large components. For the latter, e.g., modern jet-aircraft components, giant hydraulically operated presses are used, which can develop forces of 50,000 tons and mo

16、re.w 闭式模锻用于相当小的零件大批量快速生产闭式模锻用于相当小的零件大批量快速生产，也可用于很大的零件。对后者而言，例如，也可用于很大的零件。对后者而言，例如现代现代喷气飞机零件喷气飞机零件，使用能产生，使用能产生50,000吨以上吨以上压力的巨型液力锻压机。压力的巨型液力锻压机。1.Introduction of Forgingw One valuable feature of forging is that it improves the strength of the metal by refining the structure and making it uniform; so

17、for heavy forgings, such as marine propeller shafts, an immensely powerful hydraulic press squeezes the metal with a force sometimes as great as 10,000 tones. w 锻造有价值的特性之一是它通过使金属组织锻造有价值的特性之一是它通过使金属组织均匀而均匀而改善改善强度，因此对诸如强度，因此对诸如船舶螺旋桨轴船舶螺旋桨轴之类的重型锻件，要用能达之类的重型锻件，要用能达10,000吨压力的庞吨压力的庞大而有力的液压机来大而有力的液压机来挤压挤压金

18、属。金属。1.Introduction of Forgingw Although the hydraulic forging press is a more expensive piece of equipment than a drop-forge, it has advantages beside those of giving greater strength and more uniform structure to large components. On account of the high pressure and squeezing action, it operates w

19、ith less noise and vibration than a drop-forge. w 虽然这种虽然这种液压锻机液压锻机比比落锤锻造落锤锻造要昂贵得多，要昂贵得多，但它除了能给予大零件但它除了能给予大零件较高的强度较高的强度和和更均匀更均匀的组织的组织外还有其它优点。由于较高的压力和外还有其它优点。由于较高的压力和挤压作用，它比落锤锻造挤压作用，它比落锤锻造噪声噪声及及振动振动都小得都小得多。多。1.Introduction of Forgingw As ingots（锻钢胚，钢锭）（锻钢胚，钢锭） of steel weighing 30 tonnes or more are f

20、orged in this way, manual operation is impossible and it is essential that all the manipulation of the ingot is done mechanically.w 由于这种情况下被锻钢坯重量大于由于这种情况下被锻钢坯重量大于30吨，吨，人人工操作工操作是不可能的，钢坯的所有是不可能的，钢坯的所有操作操作都必须都必须是机械化的。是机械化的。1.Introduction of Forgingw Forging refines the grain structure and improves phys

21、ical properties of the metal. With proper design, the grain flow can be oriented in the direction of principal stresses encountered in actual use. w 铸造细化金属的晶粒组织、改善其物理性能铸造细化金属的晶粒组织、改善其物理性能。通过适当的设计，可以使晶粒流动方向与。通过适当的设计，可以使晶粒流动方向与实际使用时的主应力方向一致。实际使用时的主应力方向一致。1.Introduction of Forgingw As shown in Fig.4.2,

22、 grain flow is the direction of the pattern that the crystals take during plastic deformation. Physical properties (such as strength, ductility and toughness) are much better in a forging than in the base metal, which has crystals randomly oriented.w 如图如图4.2所示，晶粒流动的方向就是在所示，晶粒流动的方向就是在塑性变塑性变形形期间结晶排列的方

23、向。锻件的物理性能期间结晶排列的方向。锻件的物理性能(如如强度、延展性和韧性强度、延展性和韧性)远好于基础金属，因为远好于基础金属，因为基础金属的晶粒是无序排列的。基础金属的晶粒是无序排列的。1.Introduction of Forgingw Forgings are consistent from piece to piece, without any of the porosity, voids, inclusions and other defects. Thus, finishing operations such as machining do not expose voids,

24、because there arent any. Also coating operations such as plating or painting are straightforward due to a good surface, which needs very little preparation.w 锻件各部分是连贯一致的，没有锻件各部分是连贯一致的，没有孔隙孔隙、空洞空洞、杂质杂质及及其它缺陷其它缺陷。因此像机加工之类的精加工工序不会受空。因此像机加工之类的精加工工序不会受空洞的影响，因为根本就不存在。另外由于锻件良好的洞的影响，因为根本就不存在。另外由于锻件良好的表面，像电镀

25、或油漆之类的表面，像电镀或油漆之类的涂装工序涂装工序就很简单，几乎就很简单，几乎不需要做准备工作。不需要做准备工作。1.Introduction of Forgingw Forgings yield parts that have high strength to weight ratio, thus are often used in the design of aircraft frame members.w 锻造生产的零件具有较高的强度重量比，所锻造生产的零件具有较高的强度重量比，所以常被用在飞机结构零件的设计中。以常被用在飞机结构零件的设计中。w A forged metal can

26、result in the following:w 锻造金属可以导致下列结果：锻造金属可以导致下列结果：w Increase length, decrease cross-section, called drawing out the metal.w 增加长度、减小横截面，称为延伸金属。增加长度、减小横截面，称为延伸金属。1.Introduction of Forgingw Decrease length, increase cross-section, called upsetting the metal.w 减小长度、增加横截面，称为镦粗金属。减小长度、增加横截面，称为镦粗金属。w Cha

27、nge length, change cross-section, by squeezing in closed impression dies.w 通过用封闭锻模挤压，改变长度和横截面。通过用封闭锻模挤压，改变长度和横截面。w This results in favorable grain flow for strong parts.w 这导致有利的晶粒流使零件坚固。这导致有利的晶粒流使零件坚固。w 1.Introduction of Forgingw 2.Common Forging Processes w 3.Die Design Consideration w 4.Tolerances

28、2.Common Forging Processes w The metal can be forged hot (above recrystallization temperatures) or cold.w 金属既可热锻金属既可热锻(高于再结晶温度高于再结晶温度)也可冷锻。也可冷锻。w Open die forgings/Hand forgings. Open die forgings or hand forgings are made with repeated blows in an open die, where the operator manipulates the work-

29、piece in the die. The finished product is a rough approximation of the die. This is what a traditional blacksmith does, and is an old manufacturing process.w 开式模锻开式模锻/手工锻手工锻：开式模锻或手工锻就是操作者操：开式模锻或手工锻就是操作者操纵工件在开式锻模中反复击打。完成的产品是锻模的纵工件在开式锻模中反复击打。完成的产品是锻模的粗糙近似物。这就是传统粗糙近似物。这就是传统铁匠铁匠干的活，是较古老的制干的活，是较古老的制造工艺。造

30、工艺。2.Common Forging Processes w Impression die forgings/Precision forgings. Impression die forgings and precision forgings are further refinements of the blocker forgings. The finished part more closely resembles the die impression.w 压模锻压模锻/精密锻：精密锻：压模锻和精密锻是雏形模锻压模锻和精密锻是雏形模锻的进一步改进。完成的零件与模膛更的进一步改进。完成的零

31、件与模膛更相似相似。2.Common Forging Processes w Press forgings. Press forgings use a slow squeezing action of a press, to transfer a great amount of compressive force to the workpiece. Unlike an open-die forging where multiple blows transfer the compressive energy to the outside of the product, press forging

32、 transfers the force uniformly to the bulk of the material. w 压锻：压锻：压锻通过压力机缓慢的压锻通过压力机缓慢的挤压动作挤压动作将巨将巨大的压力传递给工件。不像开式模锻那样需大的压力传递给工件。不像开式模锻那样需要多次击打把压缩能量传递到零件外表面，要多次击打把压缩能量传递到零件外表面，压锻能将力均匀地传递给材料的主体。压锻能将力均匀地传递给材料的主体。2.Common Forging Processes w This results in uniform material properties and is necessary

33、for large weight forgings. Parts made with this process can be quite large as much as 125kg(260lb) and 3m(10 feet) long.w 这使材料性能一致，对大重量锻件而言是十这使材料性能一致，对大重量锻件而言是十分必要的。采用此工艺生产的零件重量可达分必要的。采用此工艺生产的零件重量可达125kg(260lb)而长度可达而长度可达3m(10 feet)。2.Common Forging Processes w Upset forgings. Upset forging increases

34、 cross-section by compressing the length, this is used in making heads on bolts and fasteners, valves and other similar parts.w 顶锻：顶锻：顶锻通过压缩长度增加横截面，用于顶锻通过压缩长度增加横截面，用于在在螺栓螺栓和和紧固件紧固件、柱塞柱塞及类似零件的头部制及类似零件的头部制造。造。2.Common Forging Processes w Roll forgings. In roll forging, a bar stock, round or flat is pl

35、aced between die rollers which reduces the cross-section and increases the length to form parts such as axles(轮轴轮轴), leaf springs(板簧板簧) etc. This is an essential form of draw forging.w 滚锻：滚锻：在滚锻时，圆的或是扁平的棒料放在在滚锻时，圆的或是扁平的棒料放在模辊之间缩小横截面增加长度制成诸如轮轴模辊之间缩小横截面增加长度制成诸如轮轴、板簧之类的零件。这是、板簧之类的零件。这是轧锻轧锻的基本形式。的基本形式。2

36、.Common Forging Processes w Swaging. Swaginga tube or rod is forced inside a die and the diameter is reduced as the cylindrical object is fed. The die hammers the diameter and causes the metal to flow inward causing the outer diameter of the tube or the rod to take the shape of the die.w 型锻：型锻：型锻型锻将

37、将圆管圆管或或圆棒圆棒强制压入锻模，强制压入锻模，随着随着圆柱形物体圆柱形物体的被压入其直径减小。锻模的被压入其直径减小。锻模锤击横断面使金属向内流动导致圆管或圆棒锤击横断面使金属向内流动导致圆管或圆棒的外径变为锻模的形状。的外径变为锻模的形状。2.Common Forging Processes w Net shape/Near-net shape forging. In net shape or near-net shape forging, forging results in wastage of material in the form of material flash and s

38、ubsequent machining operations, as shown in Fig.4.3. This wastage can be as high as 70% for gear blanks, and even 90% in the case of aircraft structural parts. w 纯型纯型/近似纯型锻近似纯型锻 ：采用纯型锻或近似纯型锻，产生：采用纯型锻或近似纯型锻，产生材料损耗的主要形式是材料损耗的主要形式是飞边飞边以及随后的机加工，如图以及随后的机加工，如图4.3所示。所示。齿轮毛坯齿轮毛坯材料损耗为材料损耗为70% ，而，而飞机结构零飞机结构零件

39、件的材料损耗甚至达的材料损耗甚至达90% 。2.Common Forging Processes w Net-shape and near-net-shape processes minimize the waste by making precision dies, producing parts with very little draft angle (less than 1). These types of processes often eliminate or reduce machining. w 纯型锻纯型锻和近似纯型锻工艺通过制作精密模具和近似纯型锻工艺通过制作精密模具并生产

40、锻模并生产锻模斜角斜角很小很小(小于小于1)的零件能使材的零件能使材料损耗最小化。此类工艺通常可以料损耗最小化。此类工艺通常可以省去省去或减或减少机加工。少机加工。2.Common Forging Processes w The processes are quite expensive in terms of tooling and the capital expenditure required. Thus, these processes can be only justified for current processes that are very wasteful where th

41、e material savings will pay for the significant increase in tooling costs.w 从从模具模具的角度而言这些工艺是相当昂贵的，的角度而言这些工艺是相当昂贵的，需要资金投入。因此这些工艺只有对目前很需要资金投入。因此这些工艺只有对目前很浪费的生产过程，在浪费的生产过程，在材料节约足以补偿模具材料节约足以补偿模具成本成本的大量增加时才是合理的。的大量增加时才是合理的。w 1.Introduction of Forgingw 2.Common Forging Processes w 3.Die Design Considerati

42、on w 4.Tolerances3.Die Design Consideration w Die Design Considerationw 锻模设计的考虑因素锻模设计的考虑因素w Parting surface should be along a single plane if possible, else following the contour of the part. The parting surface should be through the center of the part, not near the upper or lower edges. w 如果可能如果可能分

43、模面分模面应沿着单一平面，否则就顺应沿着单一平面，否则就顺着零件着零件轮廓轮廓方向。分模面应经过方向。分模面应经过零件中心零件中心，而不要靠近上下边缘。而不要靠近上下边缘。3.Die Design Consideration w If the parting line cannot be on a single plane, then it is good practice to use symmetry of the design to minimize the side thrust forces. Any point on the parting surface should be le

44、ss than 75from the principal parting plane.w 如果分模面不能在单一平面，利用设计的如果分模面不能在单一平面，利用设计的对对称性称性来减小来减小侧向推力侧向推力不失为一种好方法。分不失为一种好方法。分模面上任意点与模面上任意点与主分模面的主分模面的夹角应小于夹角应小于75。3.Die Design Consideration w As in most forming processes, use of undercuts should be avoided as these will make the removal of the part diffi

45、cult, if not impossible.w 如同大多数成型工艺，如果不是非用不可，如同大多数成型工艺，如果不是非用不可，尽量避免采用尽量避免采用凹槽凹槽，因为凹槽会使零件难以，因为凹槽会使零件难以取出。取出。3.Die Design Consideration w Generous fillets and radius should be provided to aid in material flow during the forging process. Sharp corners are stress-risers in the forgings, as well as make the dies weak in service.w 应提供尽可能大的应提供尽可能大的倒角倒角和和半径半径以帮助材料在锻造过程以帮助材料在锻造过程中流动。中流动。锐角锐角会增加锻件中的应力，同时在使用时削会增加锻件中的应力，同时在使用时削弱锻模。弱锻模。w Ribs should not be high or narrow; this makes it difficult for the material to flow.w 加强筋