There are a number of methods of joining metal articles together, depending on the type of metal and the strength of the joint which is required. Soldering gives a satisfactory joint for light articles of steel, copper or brass, but the strength of a soldered joint is rather less than a joint which is brazed, riveted or welded. These methods of joining metal are normally adopted for strong permanent joints.

把金属件连接在一起的方法很多，因金属的类型和所需接缝的强度不同而异。软钎焊焊接薄钢件、薄铜件和薄黄钢件，其接缝合乎要求、但其强度比硬钎焊、铆接或焊接接缝要低得多。这三种连接金属的方法通常用于高强度的永久性接合。

The simplest method of welding two pieces of metal together is known as pressure welding. The ends of metal are heated to a white heat — for iron, the welding temperature should be about 1300℃ — in a flame. At this temperature the metal becomes 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 clean first, for dirt will weaken the weld.‘Moreover, the heating of iron or steel to a high temperature causes oxidation, and a film of oxide is formed on the heated surfaces. For this reason, a flux 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 centre of the weld. A number of different types of weld may be used, but for fairly thick bars of metal, a vee-shaped weld should normally be employed. It is rather stronger than the ordinary butt weld.

把两块金属焊接在一起的最简单方法称为压焊。用火焰把每块金属的端部加热到白热状态——铁的焊接温度应当为1300℃左右。在这种高温下，金属变成塑性体。然后，再把接头强压在一起或锤击在一起，最后把接缝弄光滑。必须注意，首先保证焊件接头表面十分清洁，因为污物会减弱焊缝强度。此外，将铁或钢加热至高温时会引起氧化作用，从而在加热表面上形成一层氧化膜。为此，要把某种助焊剂用在加热金属上。当达到焊接的高温时，助焊剂便熔化，并将氧化物同其他可能有的杂质一起溶解在其中。再将金属表面强压在一起、助焊剂即被从焊缝中间挤压出来。焊缝的形式可有多种多样，但对于粗焊的金属件，通常应采用V形焊缝。它比普通的对接焊缝强度高得多。

The heat for fusion welding is generated in several ways, depending on the sort of metal which is being welded and on its shape. An extremely hot flame can be produced from an oxy-acetylene torch. For certain welds an electric arc is used. In this method, an electric current is passed across two electrodes, and the metal surfaces are placed between them. The electrodes are sometimes made of carbon, but more frequently they are metallic. The work itself constitutes one of them and the other is an insulated filler rod. An arc is struck between the two, and the heat which is generated melts the metal at the weld. A different method is usually employed for welding sheets or plates of metal together. This is known as spot welding. Two sheets or plates are placed together with a slight overlap, and a current is passed between the electrodes. At welding temperature, a strong pressure is applied to the metal sheets. The oxide film, and any impurities which are trapped between the sheets, are squeezed out, and the weld is made.

熔焊所需要的热量可用几种方法产生，选用时要根据待焊金属的品种及其形状而定。氧乙炔焊炬可产生炽热的火焰。对于某些焊接可使用电弧焊。采用这种方法时，让电流通过两个电极，而金属面则置于两极之间。电极有时是用碳制成的，但较常见的是金属电极。工件本身构成其中一个电极，另一极则是绝缘的填充焊条。当在两个电极间触发出电弧时，所产生的热量即将焊接处的金属熔化。把金属板焊接在一起通常还采用称为点焊的方法。其做法是，先把两块金属板的板边搭接在一起，再在两个电极间通上电流。达到焊接温度时，对金属板施加强大的压力。氧化膜以及被夹在两板之间的任何杂质就会被挤压出来，焊接便完成了。

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