金屬鑄造過程外文翻譯

1、<p><b>　　附錄1：英文資料</b></p><p>　　Metal-Casting Processes</p><p>　　Abstract-Following a description of the fundamentals of solidification of metals in the preceding chapter and the

2、 roles of fluid flow and heat transfer in molds, we now describe in detail:</p><p>　　Characteristics of expendable-mold and permanent-mold processes.</p><p>　　Applications advantages, and limita

3、tions of common casting processes.</p><p>　　Casting of single crystals. </p><p>　　Inspection techniques for castings.</p><p>　　Brief review of foundries and their automation.</p&

4、gt;<p>　　Typical products made by casting: engine blocks, crankshafts, hubcaps, power tools, turbine blades, plumbing, zipper teeth, dies and molds, gears, railroad wheels, propellers, office equipment, statues, a

5、nd housings.</p><p>　　Alternative processes: forging, powder metallurgy, machining, and fabrication.</p><p>　　Introduction</p><p>　　The first metal castings were made during the per

6、iod from 4000 to 3000 B.C., using stone and metal molds for casting copper. Various casting processes have been developed over time, each with its own characteristics and applications (see also Fig. 1.7a), to meet specif

7、ic engineering and service requirements (Table 11.1). A large variety of parts and components are made by casting, such as engine blocks, crankshafts, automotive components and power trains (Fig. 11.1), agricultural and

8、railroad eq</p><p>　　Two trends have had a major impact on the casting industry .The first is the mechanization and automation of the casting process, which has led to significant changes in the use of equip

9、ment and labor. Advanced machinery and automated process-control systems have replaced traditional methods of casting. The second major trend has been the increasing demand for high-quality castings with close dimensiona

10、l tolerances.</p><p>　　This chapter is organized around the major classifications of casting practices (see Fig.Ⅱ.2 in the Introduction to Part Ⅱ). These classifications are related to mold materials, moldin

11、g processes, and methods of feeding the mold with molten metal.</p><p>　　The major categories are as follows:</p><p>　　Expendable molds, which typically are made of sand, plaster, ceramics, and

12、similar materials and generally are mixed with various binders (bonding agents) for improved properties. A typical sand mold consists of 90% sand, 7% clay, and 3% water. As described in Chapter 8, these materials are ref

13、ractories (that is, they are capable of withstanding the high temperatures of molten metals). After the casting has solidified, the mold is broken up to remove the casting.</p><p>　　Permanent molds, which ar

14、e made of metals that maintain their strength at high temperatures. As the name implies, they are used repeatedly and are designed in such a way that the casting can be removed easily and the mold used for the next casti

15、ng. Metal molds are better heat conductors than expendable nonmetallic molds (see Table 3.1); hence, the solidifying casting is subjected to a higher rate of cooling, which in turn affects the microstructure and grain si

16、ze within the casting.</p><p>　　Composite molds, which are made of two or more different materials (such as sand, graphite, and metal) combining the advantages of each material. These molds have a permanent

17、and an expendable portion and ate used in various casting processes to improve mold strength, control the cooling rates, and optimize the overall economics of the casting process.</p><p>　　The general charac

18、teristics of sand casting and other casting processes are given in Table 11.2. Almost all commercially used metals can be cast. The surface finish obtained is largely a function of the mold material; although, as expecte

19、d, sand castings generally have rough, grainy surfaces. Dimensional tolerances generally are not as good as those in machining and other net-shape processes. However, intricate shapes can be made by casting, such as cast

20、-iron engine blocks and very large propell</p><p>　　Because of their unique characteristics and applications, particularly in manufacturing microelectronic devices (PartⅤ), basic crystal-growing techniques a

21、lso are described in this chapter, which concludes with a brief overview of modern foundries.</p><p>　　Expendable-Mold Casting Processes</p><p>　　The major categories of expendable-mold casting

22、are sand, shell mold, plaster mold, ceramic mold, evaporative pattern, and investment casting.</p><p>　　11.2.1 Sand casting</p><p>　　The traditional method of casting metals is in sand molds and

23、 has been used for millennia. Sand casting is still the most prevalent form of casting; in the United States alone, about 15 million tons of metal are cast by this method each year. Typical applications of sand casting i

24、nclude machine bases, large turbine impellers, propellers, plumbing fixtures, and numerous components for agricultural and railroad equipment. The capabilities of sand casting are given in Table 11.2.</p><p>

25、;　　Basically, sand casting consists of (a) placing a pattern (having the shape of the desired casting) in sand to make an imprint, (b) incorporating a gating system, (c) removing the pattern and filling the mold cavity w

26、ith molten metal, (d) allowing the metal to cool until it solidifies, (e) breaking away the sand mold, and (f) removing the casting(Fig.11.2).</p><p>　　Sands. Most sand-casting operations use silica sand (Si

27、O2) as mold material. Sand is inexpensive and is suitable as mold material because of its high-temperature characteristics and high melting point. There are two general types of sand: naturally bonded (bank sand) and syn

28、thetic (lake sand). Because its composition can be controlled more accurately, synthetic sand is preferred by most foundries. For proper functioning, mold sand must be clean and preferably new.</p><p>　　Seve

29、ral factors are important in the selection of sand for molds, and it involves certain tradeoffs with respect to properties. Sand having fine, round grains can be packed closely and, thus, forms a smooth mold surface. Alt

30、hough fine-grained sand through pores. Good permeability of molds and cores allows gases and steam evolved during the casting to escape easily. The mold also should have good collapsibility to allow for the casting to sh

31、rink while cooling and, thus, to avoid defects in the ca</p><p>　　Types of sand molds. Sand molds (Fig.11.3) are characterized by the types of sand that comprise them and by the methods used to produce them.

32、 There are three basic types of sand molds: green-sand, cold-box, and no-bake molds. The most common mold material is green molding sand, which is a mixture of sand, clay, and water. The term “green” refers to the fact t

33、hat the sand in the mold is moist or damp while the metal is being poured into it. Green-sand molding is the least expensive method of maki</p><p>　　In the cold-box mold process, various organic and inorgani

34、c binders are blended into the sand to bond the grains chemically for greater strength. These molds are more accurate dimensionally than green-sand molds but are more expensive. In the no-bake mold process, a synthetic l

35、iquid resin is mixed with the sand, and the mixture hardens at room temperature. Because the bonding of the mold in this and in the cold-box process takes place without heat, they are called cold-setting processes.</p

36、><p>　　Sand molds are oven dried (baked) prior to pouring the molten metal; they are stronger than green-sand molds and impart better dimensional accuracy and surface finish to the casting. However, this method

37、 has the following drawbacks: (a) distortion of the mold is greater, (b) the castings are more susceptible to hot tearing because of the lower collapsibility of the mold, and (c) the production rate is lower because of t

38、he considerable drying time required.</p><p>　　The flask, which supports the mold itself. Two-piece molds consist of a cope on top and a drag on the bottom; the seam between them is the parting line. When mo

39、re than two piece are used in a sand mold, the additional parts are called cheeks.</p><p>　　A pouring basin or pouring cup, into which the molten metal is poured.</p><p>　　A sprue, basin or pour

40、ing cup, into which the molten metal is poured.</p><p>　　The runner system, which has channels that carry the molten metal from the sprue to the mold cavity. Gates are the inlets into the mold cavity.</p&

41、gt;<p>　　Risers, which supply additional molten metal to the casting as it shrinks during solidification. Two types of risers, a blind riser and an open riser, are shown in Fig.11.3.</p><p>　　Cores, w

42、hich are inserts made from sand. They are placed in the mold to form hollow regions or otherwise define the interior surface of the casting. Cores also are used on the outside of the casting to form features such as lett

43、ering on the surface of a casting or deep external pockets.</p><p>　　Vents, which are placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the mold and the co

44、re. Vents also exhaust air from the mold cavity as the molten metal flows into the mold.</p><p>　　Patterns. Patterns are used to mold the sand mixture into the shape of the casting and may be made of wood, p

45、lastic, or metal. The selection of a pattern material depends on the size and shape of the casting, the dimensional accuracy and the quantity of casting required, and the molding process. Because patterns are used repeat

46、edly to make molds, the strength and durability of the material selected for a pattern must reflect the number of casting that the mold will produce. Patterns may be made </p><p>　　Patterns can be designed w

47、ith a variety o f features to fit specific applications and economic requirements. One-piece patterns, also called loose or solid patterns, generally are used for simpler shapes and low-quantity production; they generall

48、y are made of wood and are inexpensive. Split patterns are two-piece patterns, made such that each part forms a portion of the cavity for the casting; in this way, castings with complicated shapes can be produced. Match-

49、plate patterns are a common type o</p><p>　　An important development in molding and pattern making is the application of rapid prototyping (Chapter 20). In sand casting, for example, a pattern can be fabrica

50、ted in a rapid prototyping machine and fastened to a backing plate at a fraction of the time and cost of machining a pattern. There are several rapid prototyping techniques with which these tools can be produced quickly.

51、</p><p>　　Pattern design is a critical aspect of the total casting operation. The design should provide for metal shrinkage, ease of removal from the sand mold by means of a taper or draft (Fig.11.5), and pr

52、oper metal flow in the mold cavity. These topics are described in greater detail in Chapter 12.</p><p>　　Cores. For castings with internal cavities or passages, such as those found in an automotive engine bl

53、ock or a valve body, cores are utilized. Cores are placed in the mold cavity to form the interior surfaces of the casting and are removed from the finished part during shakeout and further processing, like molds, cores m

54、ust posse strength, permeability, ability to withstand heat, and collapsibility; hence, cores are made of sand aggregates. The core is anchored by core prints, which are recesses</p><p>　　Cores generally are

55、 made in a manner similar to that used in mold making; the majority is made with shell (see Section 11.2.2), no-bake, or cold-box processes. Cores are shaped in core boxes, which are used in much the same way that patter

56、ns are used to form sand molds. </p><p>　　Sand-molding machines. The oldest known method of molding, which is still used for simple castings, is to compact the sand by hand hammering (tamping) or ramming it

57、 around the pattern. For most operations, however, the sand mixture is compacted around the pattern by molding machines. These machines eliminate arduous labor, offer high-quality casting by improving the application and

58、 distribution of forces, manipulate the mold in a carefully controlled manner, and increase production rate.</p><p>　　In vertical flaskless molding, the halves of the pattern form a vertical chamber wall aga

59、inst which sand is blown and compacted (Fig.11.7). Then the mold halves are packed horizontally with the parting line oriented vertically and moved along a pouring conveyor. This operation is simple and eliminates the ne

60、ed to handle flasks, allowing for very high-production rates, particularly when other aspects of the operation (such as coring and pouring) are automated.</p><p>　　Sandslingers fill the flask uniformly with

61、sand under a high-pressure stream; they are used to fill large flasks and are operated typically by machine. An impeller in the machine throws sand from its blades (or cups) at such high speeds that the machine not only

62、places the sand but also rams it appropriately.</p><p>　　In impact molding, the sand is compacted by a controlled explosion or instantaneous release of compressed gases. This method produces molds with unifo

63、rm strength and good permeability.</p><p>　　In vacuum molding (also known as the V process), the pattern is covered tightly with a thin sheet of plastic. A flask is placed over the coated pattern and is fill

64、ed with dry, binderless sand. A second sheet of plastic then is placed on top of the sand, and a vacuum action compact the sand so that the pattern can be withdrawn. Both halves of the mold are made this way and assemble

65、d. During pouring, the mold remains under a vacuum but the casting cavity dose not. When the metal has solidified, th</p><p>　　The sand-casting operation. After the mold has been shaped and the cores have b

66、een placed in position, the two halves (cope and drag) are closed, clamped, and weighted down to prevent the separation of the mold sections under the pressure exerted when the molten metal is poured into the mold cavity

67、. A complete sequence of operations in sand casting is shown in Fig.11.8.</p><p>　　After solidification, the casting is shaken out of its mold, and the sand and oxide layers adhering to the casting are remov

68、ed by vibration (using a shaker) or by sand blasting. Casting also are cleaned by blasting with steel shot or grit (shot blasting; Section 26.8). The riser and gates are cut off by oxyfuel-gas cutting, sawing, shearing,

69、and abrasive wheels; or they are trimmed in dies. Gates and risers on steel castings also may be removed with air carbon-arc (Section 30.8) or torches. Cast</p><p>　　The casting subsequently may be heat trea

70、ted to improve certain properties required for its intended service use; these processes are important, particularly for steel castings. Finishing operations may involve machining, straightening, or forging with dies (si

71、zing) to obtain final dimensions. Inspection is important final step and is carried out to ensure that the casting meets all design and quality-control requirements.</p><p>　　Rammed-graphite molding. In this

72、 process, rammed graphite (Section 8.6) is used to make molds for casting reactive metals, such as titanium and zirconium. Sand cannot be used because these metals react vigorously with silica. The molds are packed like

73、sand molds, air dried, baked at 175°C, fired at 870°C, and then stored under controlled humidity and temperature. The casting procedures are similar to those for sand molds.</p><p>　　11.2.2 Shell m

74、olding</p><p>　　Shell molding first was developed in the 1940s and has grown significantly because it can produce many types of castings with close dimensional tolerances and a good surface finish at low cos

75、t, Shell-molding applications include small mechanical parts requiring high precision, such as gear housings, cylinder heads, and connecting rods. The process also is used widely in producing high-precision molding cores

76、. The capabilities of shell-mold casting are given in Table 11.2.</p><p>　　In this process, a mounted pattern made of a ferrous metal or aluminum is (a) heated to a range of 175°C to 370°C, (b) coa

77、ted with a parting agent (such as silicone), and (c) clamped to a box or chamber. The box contains fine sand, mixed with 2.5 to 4% of a thermosetting resin binder (such as phenol-formaldehyde) that coats the sand particl

78、es. Either the box is rotated upside down (Fig.11.9) or the sand mixture is blown over the pattern, allowing it to coat the pattern.</p><p>　　The assembly then is placed in an oven for a short period of time

79、 to complete the curing of the resin. In most shell-molding machined, the oven consists of a metal box with gas-fired burners that swing over the shell mold to cure it. The shell hardens around the pattern and is removed

80、 from the pattern using built-in ejector pins. Two half-shells are made in this manner and are bonded or clamped together to form a mold.</p><p>　　The thickness of the shell can be determined accurately by c

81、ontrolling the time that the pattern is in contact with the mold. In this way, the shell can be formed with the required strength and rigidity to hold the weight of the molten liquid. The shells are light and thin (usual

82、ly 5 to 10 mm), and consequently, their thermal characteristics are different from those for thicker molds.</p><p>　　Shell sand has a much lower permeability than the sand for green-sand molding, because a s

83、and of much smaller grain size is used for shell molding. The decomposition of the shell-sand binder also produces a high volume of gas. Consequently, unless the molds are vented properly, trapped air and gas can cause s

84、erious problems in the shell molding of ferrous castings. The high quality of the finished casting can reduce cleaning, machining, and other finishing costs significantly. Complex shapes can</p><p><b>

85、　　附錄2：中文翻譯</b></p><p><b>　　金屬鑄造過程</b></p><p>　　根據(jù)上一章對金屬成型原則的描述以及熱在模具中的傳導(dǎo)和流動，我們可以將金屬鑄造過程詳細(xì)的表述為：</p><p>　　可消耗模具鑄造和永久模具鑄造，常用鑄造過程的應(yīng)用優(yōu)勢和局限性；</p><p><b&g

86、t;　　單晶鑄件；</b></p><p><b>　　鑄件的檢驗方法；</b></p><p>　　鑄造廠的簡要經(jīng)驗和鑄造方法的自動操作。</p><p>　　鑄件的主要產(chǎn)品：發(fā)動機墊塊、機軸、輪轂罩、動力工具，渦輪刀片，鋁制品，拉練齒、壓鑄模、澆注模、齒輪、列車輪、推進(jìn)器、辦公設(shè)備、雕像和機架。</p><p

87、>　　可選的方法有：鍛造、粉末冶金、機加和修配。</p><p><b>　　11．1介紹</b></p><p>　　金屬鑄造工藝早在公元前4000年到公元前3000年就出現(xiàn)了。用石頭和金屬模具鑄造銅器。接下來的發(fā)展使得鑄造的方法多種多樣，每種方法都有各自的應(yīng)用范圍和使用特點（見圖17.a），有詳細(xì)的加工方法和使用要求（表11.1給出）。絕大部分的零件及部件都

88、是由鑄造加工得到的。諸如發(fā)動機墊塊、機軸、推進(jìn)器部件動力機車（圖11.1）農(nóng)業(yè)及鐵路設(shè)備、管道、管道緊固裝置、動力刀具、槍膛、平底鍋、辦公器材和渦輪機的大部分零件。</p><p>　　工業(yè)上影響鑄造的趨勢主要有兩個。第一個是機械自動化的鑄造方法，這種方法在設(shè)備使用和勞動強度方面有著重大意義。先進(jìn)的機械和自動控制系統(tǒng)取代了傳統(tǒng)的鑄造方法。第二個主要趨勢提高了鑄件的質(zhì)量和尺寸公差要求。</p><

89、;p>　　這一章列舉了鑄造的主要典型實例，涉及了模具材料、加工方法和澆注方法。</p><p><b>　　主要有如下幾類：</b></p><p>　　可消耗模具，典型的有沙模、石膏模、陶瓷模等近似材料模具。這些材料均需加入多種粘結(jié)劑（用來粘合）提高模具的性能。一個典型的沙模由 90%的沙，7%的粘土，和3%的水組成。如第8章所說的，這些材料都是難熔材料（就是

90、說這些物質(zhì)在熔融的金屬熔液中可以保持不變）。待鑄造成型后，把模具破壞掉，取出鑄件。</p><p>　　永久鑄模，這類模具是用金屬制成的，并可以在高溫下保持原狀。顧名思義，這種模具可以循環(huán)使用，并且使制件很容易從模具中取出，投入下一次使用。金屬模具比不可控的非金屬模具的導(dǎo)熱性更好（見表3.1）。因此，鑄件凝固時必須頻繁冷卻，冷卻速度會影響鑄件內(nèi)部微觀結(jié)構(gòu)晶粒的大小。</p><p>　　組

91、合模，這種模具由兩種或兩種以上的材料組成（如沙、石墨和金屬），性能比任一種組成成分優(yōu)越。這類模具有永久和可消耗兩部分組成，可以 廣泛運用于鑄造業(yè)，它可以改善模具的強度、控制鑄件的冷卻速度，使鑄造過程最經(jīng)濟(jì)。</p><p>　　沙模和其他鑄造方法的一般特點見表11.2。幾乎所有的商用金屬均可以被鑄造。鑄件表面精度的獲得很大程度上取決于模具材料。盡管如我們所想，沙模的表面顆粒很大，又粗糙，尺寸公差也不如機加或其它成

92、型加工方法所獲得的公差。但是，沙模卻能鑄造出復(fù)雜結(jié)構(gòu)的零件，如鑄鐵發(fā)動機墊塊和大型遠(yuǎn)洋輪用推進(jìn)器。</p><p>　　由于它們的唯一特點和應(yīng)用，主要用于制造微電設(shè)備（第5部分），基本晶體生成技術(shù)也在本章中表達(dá)，主要包含了現(xiàn)代鑄造廠里的一些觀點的摘要。</p><p>　　11．2可消耗模具的鑄造方法</p><p>　　可消耗模具主要類型有沙模、脫殼模、石膏模、陶

93、瓷模，還有蒸發(fā)和熔模鑄造等方式。</p><p><b>　　11.2.1沙模</b></p><p>　　傳統(tǒng)的鑄造金屬方法就是用沙模，并且這種方法已經(jīng)有幾千年的歷史了。在美國，沙模依舊是最普遍的鑄造方式，每年有大約一千五百萬噸的金屬是用這種方法鑄造出來的。沙模主要用于鑄造機械的基礎(chǔ)，大型渦輪的推進(jìn)器、管道、管道緊固件、還有許多農(nóng)業(yè)用品和鐵路設(shè)備。</p>

94、;<p>　　沙模的性能在表 11.2中給出。</p><p>　　沙模的主要組成是a)防置型（包含鑄件的形狀）鑄件的形狀全部在砂型中；b)合成控制系統(tǒng)；c)去除形，在砂型中注入金屬熔液；d)金屬在凝固后冷卻；e)剝離型沙模；f)去除鑄件型。（圖11.2）</p><p>　　沙子。多數(shù)的沙模是由硅沙作為沙模材料的。沙子不但便宜而且它有高溫特性和高熔點，這些性能與模具材料相符

95、合。沙子有兩類：自然沙（岸沙）和合成沙（湖沙）。由于沙子的組成可以精確的控制，合成沙是許多鑄造廠的首選材料，由于這種特有性能，沙模又環(huán)保又經(jīng)濟(jì)。</p><p>　　許多廠家對模具沙的選擇很重視，并將其作為一種固定的交易方式。沙子也有精度，沙子的圓形顆?？梢詭缀跆顫M，從而形成模具光滑的表面。（通過氣孔排氣）。模具和心部有良好的透氣性，在鑄件脫離時水汽和氣體更容易蒸發(fā)。因為模具冷卻收縮，沙模也極易崩裂，因此要在鑄造

96、時避免這個和熱脹裂一樣的缺點（見圖10.12）。</p><p>　　沙模的類型。沙模（圖11.13）分類是根據(jù)組成沙的類型及生產(chǎn)使用方式劃分的。沙模有三種類型：濕沙模、低溫沙模和非烤沙模，最常用的模具材料是是濕沙模沙，這種材料由沙子、粘土和水混合而成。術(shù)語中“濕”指的是當(dāng)金屬液體注入模具時，沙子在模具中是潮的或是濕的。濕沙造型是制作模具最經(jīng)濟(jì)的一種方法。模具的表面是干燥的，無論將其在空氣中或在干燥的地方保存，模

97、具都會自燃。由于他的高強度，這些模具用來鑄造大型鑄件。</p><p>　　在低溫模具鑄造時，加入了許多有機和無機粘結(jié)劑，以化合的方法粘結(jié)顆粒產(chǎn)生更大的強度。這類模具比濕沙模的尺寸精度更高但更貴。在非烤模具的加工中，混入了一種合成樹脂液體，它會在室溫中變硬。由于模具以這樣的方式粘結(jié)，低溫加工不需熱量，這兩種方式合稱為冷加工方法。</p><p>　　沙模在注入金屬液體之前應(yīng)烘干（烤干）。這

98、樣的模具比濕沙模具更堅固。并在尺寸和表面光潔度上也比濕沙模好，但這種方法有以下缺點：a)變形大；b)由于模具的崩潰性小鑄件對熱脹敏感；c)由于烘干時間長，生產(chǎn)率低。</p><p>　　支撐模具本身的瓶子，兩個半模由一個管從頂部貫穿到模具的底部。它們的接縫是兩條分開的線。當(dāng)模具多于兩個半模組成，則附加的部分稱為頰。</p><p>　　澆注池或澆注帽，是金屬液體注入的地方。</p&g