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【正文】 面被壓合在一起,而助焊劑就從焊縫中間被擠出。此外,加熱鑄鐵或鋼到高溫會引起氧化井在焊接表面形成氧化皮。最后再將焊縫清理千凈。The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heatfor iron, the welding temperature should about 1300Cin a flame[fleim]. At this temperature the metal bees plastic. The ends are then pressed or hammered together, and the joint is smoothed off. Care must be taken to ensure that the surfaces are thoroughly[5WQrElI] clean first, for dirt will weaken the weld. Moreover, the heating of iron or steel to a high temperature causes oxidation[Cksi5deiFEn], and a film[film] of oxide[5Cksaid] is formed on the heated surfaces. For this reason, a flux[flQks] is applied to the heated metal. At welding heat, the flux melts, and the oxide particles are dissolved in it together with any other impurities which may be present. The metal surfaces are pressed together, and the flux is squeezed out from the center of the weld. A number of different types of weld may be used, but for fairly thick bars of metal, a vshaped weld should normally be employed[im5plCi]. It is rather stronger than the ordinary but weld.把兩件金屬焊在一起的最簡單的方法稱做壓力焊。Soldering gives a satisfactory joint for light articles of steel, copper or brass[brB:s], but the strength of a soldered joint is rather less than a joint which is brazed[breiz], riveted[5rivit] or welded[weld]. These methods of joining metal are normally adopted[E5dCptid] for strong permanent[5pE:mEnEnt] joints.軟釬焊能為輕型鋼件、銅件和黃銅件生產(chǎn)滿意的焊縫,但軟釬焊的焊縫強度比起硬釬焊、鉚接和焊接來要弱些。軟釬焊中最重要的工序之一就是清理焊縫表面。而常常含有鉍和鎘。Soldering[5sCldEriN] is the process of joining two metals by a third metal to be applied in the molten state. Solder[5sCldE, 5sC(:)] consists of tin and lead, while bismuth[5bizmEW] and cadmium[5kAdmiEm] are often included to lower the melting point. One of the most important operations in soldering is that of cleaning the surface to be joint, this may be done by some acid cleaner.軟焊是要用溶融狀態(tài)的第三種金屬來使兩件金屬連接在一起的工藝。為鍛件加熱,溫度通常是以肉眼來判斷的,但在生產(chǎn)大量相同鍛件的場合,要鍛造的坯件是在有高溫計指示溫度的爐子中來加熱,并且常常是自動控制的。鍛造將在大約與輥軋同樣的溫度下進(jìn)行,這種工藝正像軋制那樣可改善金屬的物理性能。因為用壓力機鍛造,變形更加深透。這一方法廣泛用來制造鋼件和黃鋼件。In drop forging, a piece of metal, roughly[5rQflI] or approximately of the desired[di5zaiE] shape, is placed between die faces having the exact form of the finished piece, and forced to take thin form by drawing the dies together. Large ingots are now almost always forged with hydraulic presses instead of with steam hammers, since the work done by a press goes deeper. Further, the press can take a cooler ingot and can work to closer dimensions[di5menFEn]. The forging should be done at about the same temperature as rolling[5rEuliN]。然而落錘鍛造可以鍛制形狀復(fù)雜而不規(guī)則的鍛件,因而較為經(jīng)濟。金屬上的壓力衰減較快,因此生產(chǎn)成本比較低。In the forging press, a greater proportion of the total work put into the machine is transmitted[trAnz5mit] to the metal than in a drop hammer press. Much of the impact of the drop hammer is absorbed by the machine and foundation. Press reduction of the metal is faster, and the cost of operation is consequently lower. Most press forgings are symmetrical[si5metrikEl] in shape, having surfaces which are quite smooth, and provide a closer tolerance[5tClErEns] than is obtained by a drop hammer. However, many parts of irregular[i5re^julE] and plicated shapes can be forged more economically by drop forging. Forging press is often used for sizing operations on parts made by other forging processes.鍛壓機比落錘鍛,輸入到機器里的總能量中有更大部分的能量被傳輸?shù)浇饘倥髁仙稀R虼丝缮a(chǎn)更加復(fù)雜形狀的鍛件。模具可由各白獨立的單元裝配而成,即把所有個別模腔都放到一起,組成整體。通常要求鍛錘僅一個沖程就完成鍛造工藝。For small press forgings, closed impression dies are used and only one stoke of the ram[rAm] is normally required to perform[pE5fC:m] the forging operation. The maximum[5mAksimEm] pressure is built up at the end of the stroke which forces the metal into shape. Dies may be mounted[maunt] as separate units, or all the cavities may be put into single block. For small forgings, individual[7indi5vidjuEl] die unites are more convenient. There is some difference in the design of dies for different metals。這些壓力機都是立式的,可能是機械操作也可能是液壓操作的。4. ForgingPress forging[5fC:dViN] employs a slow squeezing[skwi:z] action in deforming[di:5fC:m] the plastic metal, as contrasted with the rapidimpact[5impAkt] blows of a hammer. The squeezing action is carried pletely to the center of the part being pressed, thoroughly working the entire section[5sekFEn]. These presses are the vertical[5vE:tikEl] type and may be either mechanically[mi5kAnikEli] or hydraulically[hai5drC:lik] operated. The mechanical presses, which are faster operating and most monly used, range in capacity[kE5pAsiti] from 500 to 1000 tons.與錘鍛的快速沖擊不同,壓力機鍛造是用緩慢的擠壓作用使塑性金屬變形。 這種作用隨著溫度的升高而增加,甚至某些合金比另一些合金更為明顯。高溫在模具上的損壞作用已經(jīng)成為阻礙、延緩高溫模鑄發(fā)展的主要因素。低溫類合金具有低生產(chǎn)成本和低的模具維修費用等優(yōu)點。這些合金可以進(jìn)一步進(jìn)行分類為低溫類合金和高溫類合金。A relatively[5relEtIvlI] wide range of nonferrous alloys can be diecast. The principal base metals used, in order to mercial importance, are zinc, aluminum, copper, magnesium[mA^5ni:zjEm], lead, and tin. The alloys may be further classified as lowtemperature alloys and hightemperature alloys。而澆注金屬液到這些模子中生產(chǎn)出的鋼塊被稱為鋼錠。也有一種特殊模型,在該模型中可以鑄造大型鋼塊。金屬模是由兩個中空的部件組成,它們應(yīng)被聯(lián)結(jié)在一起以便將金屬液澆入模箱中。From the cupola, the cast iron flows into ladles[5leidl] of different size, and from these ladles it is poured into the molds.從沖天爐中出來的鐵水流入到不同規(guī)格的鐵水包中,并從這些鐵水包中被澆注到模型中。The place where the metals are cast is called a foundry. The most important of cast metals is cast iron which is made from pig iron by remelting it in a special melting furnace[5fE:nis] called a cupola[5kju:pElE].鑄造金屬的地方叫做鑄造車間。這些金屬中,鑄鐵,由于其低熔點,低價格和易控制,因而其鑄造適應(yīng)性是最突出的,而且使用也遠(yuǎn)比所有其他金屬多。實際上所有金屬在成分上也是變化的,而合金也可以鑄造。Foundry[5faundri] processes consist of making molds, preparing and melting[melt] the metal, pouring[pC:, pCE] the metal into the molds, and cleaning the castings. The product of the foundry is a casting, which may vary from a fraction[5frAkFEn] of a kilogram to several hundred tons. It may also vary in position[kCmpE5ziFEn] as practically all metal
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