焊接專業(yè)英語課文翻譯
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1.Pattern Material
Wood is the most common material for patterns. It is easy to work and readily available. Properly selected and kiln-dried mahogany, walnut, white pine, and sugar pine are often used. Sugar pine is most often used because it is easily worked and is generally free from warping and cracking. Moisture in the wood should be about 5 to 6% to avoid warping, shrinking, or expanding of the finished pattern.
Metal patterns may be loose or mounted. If usage warrants a metal pattern, then the pattern probably should be mounted on a plate and include the gating system. Metal is used when a large number of castings are desired from a pattern or when conditions are too severe for wooden patterns. Metal patterns wear well. Another advantage of a metal pattern is freedom from warping in storage. Commonly a metal pattern is itself cast from a master pattern and can be replaced readily if damaged or worn.
Patterns are made of plaster and plastics. Plaster patterns are easy to make; they can be cast where original molds are available. However, plaster is brittle and not suitable for molding large numbers of sand castings. Plastics serve in several ways for pattern making. Some conventional patterns are made of abrasion-resistant plastics with cost and durability between wood and metal. Another use of certain plastics is to make emergency patterns quickly or to salvage worn or broken patterns.
1.模型材料
木板是常用的材料，很容易去做并且很通用，普通的選擇是桃花芯木，胡桃木，白松和糖松。糖松是最常用的，很容易去制作而且很容易收縮和開裂很自如。在完成的模型中水分應(yīng)控制在5%-6%之間為防止變形、收縮、膨脹。
金屬模型可能是實體的或模板的，模型可能被鑄造在一個金屬板上，包括澆注系統(tǒng)。當大量的鑄件都特別需要一個模型，或者條件非常嚴格時，就要用金屬，金屬模板的耐磨性很好。另一個優(yōu)點是它不受儲藏變形的限制。一般來說，金屬模板由一個主要模板鑄造而成，如果它被損壞或磨損了也很容易被替代。
模板由石膏和塑料制成。石膏模板很容易制作，它們可以被制作當原始鑄型，然而，石膏是容易損壞的，并且不適合于數(shù)量多的砂型鑄造，塑料在模板制作中可以有很多方式，一般現(xiàn)用的模板都由持久磨損的塑料和介于木頭和金屬之間的耐磨材料制成。塑料的另一種用途是能快速做成應(yīng)急模板或者用舊的或者破損的模板。
2.Cleaning , Finishing Castings
After solidification and removal from the molds, most castings require some cleaning and finishing. These may involve all or several of the following steps:
1. Removing cores.
2. Removing gates and risers.
3. Removing fins and rough spots from the surface.
4. Cleaning the surface.
5. Repairing any defects.
The required operations are not always done in the same order, and the particular casting process may eliminate some of them. Because cleaning and finishing operations may involve considerable expense, some consideration should be given to them in designing castings and in selecting the casting method to be used. Often substantial savings can be effected. In recent years much attention has been given to mechanizing these operations.
Sand cores usually can be removed by shaking. Sometimes they must be removed by dissolving the core binder. On small castings, gates and risers can often be knocked off. However, on large castings, and often on small castings, they must be cut off, On nonferrous and cast iron castings this usually is done by means of an abrasive cutoff wheel, power hacksaw or bandsaw. Gates and risers on steel castings, especially large ones, are often removed by an oxyacetylene torch.
After the gates and risers are removed, small castings are often put through tumbling barrels, to remove fins, snags, and sand that adhere to the surface. Tumbling also may be used to remove cores and, in some cases, gates and risers. Frequently, some type of shot or slug material is added to the barrel to aid in the cleaning. Larger castings may be passed through a cleaning chamber on a conveyor, wherein they are subjected to blasts of abrasive or cleaning material. Large castings usually have to be finished manually, using pneumatic chisels, portable grinders, and manually directed blast hoses in separate cleaning rooms.
Although it is desirable that casting contain no defects, it is inevitable that some will occur, particularly in large castings where only one or a few of a particular design are made. Some types of defects can be repaired readily and satisfactorily by arc welding. However it is imperative that the casting be of a material that can be welded satisfactorily, that all defective areas be removed down to sound metal by grinding, or chipping, and that a sound repair weld be made.
2.清洗，整理鑄件
凝固后、清除模具，大多數(shù)鑄件需要一些清潔和整理活動。這些可能涉及所有或幾個下列步驟。
1.移除內(nèi)核。
2.移除澆注系統(tǒng)和冒口。
3.移除表面飛邊和粗糙點。
4.清理表面。
5.修理所有缺陷。
在相同的順序中所需的行動并不總是要做，特別是鑄造工藝可以消除其中的一些。由于清潔和整理的行動可能涉及相當大的開支，在設(shè)計和選擇鑄件的鑄造方法使用方面應(yīng)該給與一些考慮。往往可以獲得大量節(jié)省。近年來，更多的注意力已經(jīng)放在機械化去進行這些行動。
通過搖晃砂芯通�？梢匀コ�。有時 ，他們必須通過解散砂心粘結(jié)劑來去除。小鑄件，澆注系統(tǒng)和冒口往往可以被打掉。然而，在大型鑄件以及小鑄件，他們必須切斷。對于非鐵金屬鑄件和鑄鐵件的澆注系統(tǒng)與冒口，一般用切割砂輪、電動弓鋸或帶鋸去除。鋼鑄件的閥門和立管，尤其是大企業(yè)，往往是通過氧乙炔火焰來去除。
澆注系統(tǒng)和冒口去除以后，通常將小型鑄件放入清理滾筒內(nèi)，以去除飛邊、毛刺和鑄件表面上的粘砂。滾筒也可用于消除內(nèi)核，在某些情況下，澆注系統(tǒng)和冒口。經(jīng)常地，某些類型的炮彈或星鐵材料被添加到圓桶以協(xié)助清理。較大的鑄件可通過清理室的傳送帶，在那里他們受到研磨料的噴射或清洗材料。較大的鑄件通常都必須手工完成，采用氣動鑿子，便攜式磨床，并在單獨清洗室手動指示噴砂膠管。
盡管鑄件不含缺陷是令人期望的，但是不可避免有些缺陷也會發(fā)生，特別是在大型鑄件，只有一個或幾個特定設(shè)計的意見。通過弧焊某些類型的缺陷可以容易地修復(fù)和令人滿意的。然而，當務(wù)之急是鑄造一種材料，可以令人滿意地進行焊接，通過磨光、削可以將有缺陷的區(qū)域被刪除成為優(yōu)質(zhì)金屬，而且優(yōu)質(zhì)的焊接修補可以進行。
3.Sand Conditioning and Control
Sand used to make must be carefully conditioned and controlled in order to give satisfactory and uniform results. Ordinary silica(SiO2), zircon, or olivine ( forsterite and fayalite ) are compounded with additives to meet four requirement:
1. Refractoriness: the ability to withstand high temperatures.
2. Cohesiveness (referred to as bond): the ability to retain a given shape when packed in a mold.
3. Permeability: the ability to permit gases to escape through it.
4. Collapsibility: the ability to permit the metal to shrink after it solidifies.
Refractoriness is provided by the basic nature of the sand. Cohesiveness, bond, or strength is obtained by coating the sand grains with clays, such as bentonite, kaolin or illite, that become cohesive when moistened. Collapsibility is obtained by adding cereals or other organic materials such as cellulose, that burn out when exposed to the hot metal, thereby reducing the volume of solid bulk and decreasing the strength of the restraining sand. Permeability is primarily a function of the sand particles, the amount and types of clays or other bonding agents, and the moisture content.
Sand control. Although sand control is of concern to the designer of castings, it is a matter of great concern to the foundry worker, who is expected to deliver castings of good and consistent quality.Standard tests and procedures have been developed to maintain consistent sand quality by evaluating grain size, moisture content, clay content, mold hardness, permeability, and strength.
Grain size is determined by shaking a known amount of dry silica grains downward through a set of 11standard sieves having increasing fineness. After shaking for 15 minutes, the amount remaining in each sieve weighed, and the weights are converted into an AFS number.
Moisture content most commonly is determined by a special device which measures the electrical conductivity of a small sample of sand that is compressed between two prongs. Another device provides a continuous measure of the moisture content, by emission from a radioactive source, as the sand passes along a conveyor belt. A third method is to measure the direct weight loss from a 50-gram sample when it is subjected to a flow of air at about 110℃for 3 minutes.
Clay content is determined by washing the clay from a 50-gram sample of molding sand in water that contains sufficient sodium hydroxide to make it alkaline. After several cycles of agitation and washing in such a solution, the clay will have been removed. The remaining sand is dried and then weighed to determine the proportion of the original sample that was clay.
3.砂處理和控制
砂用于制造鑄型必須仔細調(diào)節(jié)和控制以提供滿意的服務(wù)和統(tǒng)一的結(jié)果。普通石英(二氧化硅),鋯石,或橄欖石(鎂橄欖石和鐵橄欖石)加上添加劑以滿足四個要求:
1.耐火度:耐高溫能力。
2.凝聚力(稱為債券):能夠保留一個給定的形狀時,裝在一個模具的能力。
3.透氣性:允許氣體逸出的能力。
4.退讓性:金屬凝固后收縮的能力。
耐火度是沙子的基本性質(zhì)。型砂的強度是靠包覆在砂粒表面的粘土，如膨潤土、高嶺土或伊利石加水后具有粘性而獲得的。退讓性是通過添加谷物或其他有機材料獲得,如纖維素,當暴露在熱金屬會燒毀,從而減少了固體散裝的體積和降低抑制砂的強度。透氣性是砂顆粒的主要功能,數(shù)量和粘土的類型或其他粘合劑和含水量。
防砂。盡管防砂是設(shè)計師關(guān)注的鑄件,是鑄造工人所關(guān)注的`問題，他們被期望輸送優(yōu)良和統(tǒng)一質(zhì)量的鑄件。標準測試程序已經(jīng)發(fā)展到由晶粒的大小，水分含量，粘粒含量，模具的硬度，透氣性和強度來評價保持一致的砂的質(zhì)量。
原砂粒度組成的測定方法，是把一定數(shù)量的干硅砂試樣放在一套標準篩上進行篩分，而標準篩是由十一個越來越細的篩子構(gòu)成的。搖后15分鐘,稱量剩余在每個篩子里面的數(shù)量,權(quán)重轉(zhuǎn)化為AFS數(shù)。
含水量最常見的是由一個特殊的裝置決定的,測量一個被壓縮在兩個尖頭叉子小樣本沙子的電導(dǎo)率。另一個裝置提供了一種可以連續(xù)測量含水量,通過發(fā)射從放射性源,如砂沿著輸送帶。第三種方法是從50克樣品中，當它在大約110℃進行3分鐘流動的空氣中直接測量減少量。
粘土含量是由在水中洗粘土從50克樣品的型砂含有足夠的氫氧化鈉使其堿性決定的。在這種解決方案中，經(jīng)過幾個周期的攪拌和清洗,粘土已被移除。剩下的砂干燥，,然后稱重以確定原樣品粘土的比例。
4.Investment Casting
Investment casting actually is a very old process. It existed in china for centuries, and Cellini employed a form of it in Italy in the sixteenth century. Dentists have utilized the process since 1897, but it was not until World War II that it attained industrial importance for making jet turbine blades from metals that were not readily machinable. Currently millions of castings are produced by the process each year, its unique characteristics permitting the designer almost unlimited freedom in the complexity and close tolerances he can utilize.
Investment casting involves the following steps:
1. Produce a master pattern.
2. From the master pattern, produce a master die.
3. Produce the wax patterns.
4. Assembly the wax patterns to a common wax sprue.
5. Coat the cluster with a thin layer of investment material.
6. Produce the final investment around the coated cluster.
7. Vibrate the flask to remove the entrapped air and settle the investment material around the cluster.
8. Allow the investment to harden.
9.Melt or dissolve the wax pattern to permit it to run out of the mold.
10.Preheat the mold preparatory to pouring.
11.Pouring the molten metal.
12.Remove the castings from the mold.
Fig.3-7-5 schematically shows the investment procedure wherein the investment-mold material fills the entire
Fig.3-7-5 Investment flask-casting procedure
4.熔模鑄造
熔模鑄造實際上是一個非常古老的鑄造過程。它在中國存在了幾個世紀,在十六世紀的意大利，賽里尼鉻錳鋼就以熔模鑄造的一種形式被制造。自從1897年以來，牙醫(yī)就已經(jīng)利用了這個程序，但直到第二次世界大戰(zhàn)期間，它在工業(yè)制造中獲得一定的重要地位，從金屬不易加工到加工制造噴氣渦輪葉片目前每年數(shù)以萬計的鑄件通過這個過程被生產(chǎn)出來，其獨特的特點就是允許設(shè)計者在復(fù)雜性和公差方面幾乎可以無限制地利用。
熔模鑄造包括以下步驟：
1.產(chǎn)生一個主模式。
2.從主模式，產(chǎn)生一個主模。
3.產(chǎn)生蠟?zāi)Ｊ健?/p>
4.裝配到一個共同的蠟型澆口。
5.外套集群有一層薄薄的鑄模材料。
6.在涂覆集群生成最終的鑄模。
7.在模組的周圍，振動長頸瓶移除裹入的氣體和處理熔模材料。
8.允許熔模變硬。
9.熔融或溶解蠟?zāi)Ｊ皆试S它脫離出模具。
10.預(yù)熱模具準備澆注。
11.澆注熔融金屬。
12.從模具中移出熔模。
圖3-7-5示意圖顯示了鑄造過程中,熔模鑄型材料充滿了整個瓶子。
5.Patterns
A pattern is a form used to prepare and produce a mold cavity. It is another tool in the hands of a founder. It has been said that a poor casting may be produced from a good pattern, but a good casting will not be made from a poor pattern.
The designer of a casting must look forward to the pattern to assure economical production. The design should be as simple as possible to make the pattern easy to draw from the sand and avoid more cores than necessary.
Types of patterns. Many molds are made from loose patterns. Such a pattern has essentially the shape of the casting with perhaps forms for sprues, risers, etc, attached. This is the cheapest pattern to make but the most time consuming to use. A loose pattern may be made in one or more pieces. For instance, a two-piece pattern is normally split into cope and drag parts to facilitate molding. For a part difficult to mold, some loose pieces may be removable to allow the pattern to collapse for withdrawal from the sand that would otherwise not be possible.
Patterns fastened permanently to a board or match plate are known as mounted patterns. A main advantage is that a mounted pattern is easier than a loose pattern to use and store. Another advantage is that the gating system can be mounted on a match plate, and thus the time required to cut the gating system in the mold can be eliminated. Mounted patterns cost more than loose patterns, but when many castings are to be made from a pattern, the time saved in operation warrants the cost of mounting the pattern.
A core box is essentially a type of pattern into which sand is rammed or packed to form a core as illustrated in
Fig.3-2-1 Typical core boxes
Symmetrical molds and cores, particularly in large sizes, are sometimes shaped by means of sweeps as illustrated in Fig.3-2-2. The sweep is a flat board with an outline of the cross section of the part to be made and is revolved around a central axis to clear away excess sand inside the mold.
Fig.3-2-2 Sweep pattern
5.模型
模樣是用來形成鑄件型腔的工藝裝備它是鑄工手中的另一個工具，據(jù)說質(zhì)量差的鑄件有可能是由一個好的鑄件制造的，但是好的鑄件絕不是由差的鑄件制造而成的。
鑄件的設(shè)計者希望模樣可以確保生產(chǎn)成本。設(shè)計要盡可能簡單，以便于起模，而且要避免使用過多的型芯。
模樣的類型。很多模具都是由實體模鑄成的。一個模型有基本的鑄件形狀并附有澆道、冒口等其它鑄件。這是鑄造花費最便宜的模型，但是時間花費很多。一個實體模型可以由一個或多個部分組成。例如，兩箱式模型可以裂開以便于起模，對于用其它方法難以造型的零件。為了能從型砂中取出模樣，可將整體模樣局部做成一些活塊，以便于起模。
模樣固定永久地在木板上或雙面模板就是我們熟知的模板，與單體模相比，模板的一個主要優(yōu)點是容易使用和存放。另一個優(yōu)點是澆注系統(tǒng)可以消除，模板要比實體�；ㄙM的要多，但是當批量生產(chǎn)時，節(jié)約了大量的操作。
芯核本質(zhì)上也是模樣的一種，用沙子填塞或充滿型芯例如插圖Fig3-2-1。
對稱的模型和型芯，尤其是大尺寸的。有時通過刮板的方法制造成型如插圖Fig3-2-2。刮板即平板，與大綱的橫截面的部分制造而成和繞著中心軸使旋轉(zhuǎn)去清除大量的在子模型里面的沙子。
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