苏ICP备112451047180号-6
气体保护焊
气体保护焊是利用一个与空气或氧气有关联的气体燃料燃烧过程中所释放的能量。
这些大多数最常用的燃料气体是乙炔，氢气，天然气，这主要是甲烷或者是丙烷和丁烷。这些气体必须是在氧气中燃烧而不是在空气中燃烧。空气中约有78%的氮气和21%的氧气。空气中大量的氮气不但对气焊过程毫无帮助，而且还会吸收掉大量的燃烧热量，从而大大降低了燃烧火焰的温度。少量的一些金属可以通过气体与空气混合物进行低温焊接。
最普遍有用的火焰当然是氧-乙炔火焰了。本文结合了氧气和乙炔的火焰燃烧温度大约在3300摄氏度，除了金属钨以外，这是在所有金属中熔点熔最高的。没有其他可用的燃料气体可以提供同样高的温度。这种强热熔断器接头的结合处被熔化的焊条所焊接，然后沉积在结合的地方。乙炔的热含量为1475每立方英尺，但每立方英尺所释放热量的量取决于氧气和乙炔的比例供给焊炬。
上述提到的所有的气态燃料中都含有碳和氢，并且它们都能用氧气进行助燃。因此气焊不能够以碳，氢，氧的形式存在来执行以上的金属伤害，例如：钛。有很多这样的金属。
气体保护焊还有其他的一些缺点。它缓慢而低效，而且并不集中在焊缝狭窄区域内的热。它产生的金属热畸变比其他的焊接方法要多。作为一个结果，气体保护焊是工厂很罕见使用的一种生产方法。
所有这些都是气焊的一些严重的缺点，但这并不是不是气焊的全部情况。事实上氧乙炔焊接有一个很突出的优势那就是它需要非常小的设备。基本上所需要的全部东西就是焊炬，软管，调压器，乙炔瓶和氧气瓶，所有这些部件都很小，又很轻便。
气焊火焰温度低于电弧的温度。当接头必须焊接在低熔点金属的时候，出于这样的考虑可能会使用电弧焊而不是气体保护焊，例如铅。气焊的良好服务像钎焊，焊接，一般的维修和保养，汽车车身，和金属薄板的焊接和铅的工作那样。
某些类型的焊接，如钨极氩弧焊，熔化，和等离子体炬焊接，是天然气和电力焊接组合使用，因为他们使用一连串气体特殊成分的非电化的电弧。
Gas Welding
Gas welding utilizes the energy released during combustion of a fuel gas with air or oxygen.
The most commonly used fuel gases are acetylene, hydrogen, natural gas, which is largely methane or CH4, propane, or butane. These gases must usually be burned with oxygen rather than air. Air is about 78% nitrogen and 21% oxygen. The large amount of nitrogen in air contributes nothing to the gas welding process and absorbs much of the heat of combustion, thus greatly lowering the temperature of the flame. Few metals could be welded by the low temperature of a gas-air mixture.
The most commonly used flame is of course the oxyacetylene flame. This combination of oxygen and acetylene gives a flame temperature of about 3300oC, which is above the melting point of all metals except tungsten. No other available fuel gas can provide as high a - temperature. This source of intense heat fuses the edges of the joint to be welded and also melts a filler rod, which is then deposited at the joint. The Btu content of acetylene is 1,475 Btu per cuft, but the amount of heat released per cubic foot depends on the proportions of oxygen and acetylene supplied to the torch.
All the fuel gases mentioned above contain both carbon and hydrogen, and all are burned with oxygen. Gas welding therefore cannot be performed upon metals harmed by the presence of carbon, hydrogen, or oxygen, for example, titanium. There are many such metals.
Gas welding has other disadvantages. It is slow and inefficient, and it does not concentrate the heat within the narrow area of the weld. It produces more heat distortion of the metal than other welding methods do. As a result, gas welding is rarely used as a factory production method.
All these are serious disadvantages of gas welding, but they are not the full story. Oxyacetylene welding offers an outstanding advantage in the fact that it requires very little equipment. Basically all that is needed is a torch, hose, regulators, and cylinders of acetylene and oxygen, all these components being small, portable items.
The flame temperatures of gas welding are lower than the temperatures of an electric arc. This consideration may make gas welding preferable to arc welding when joints must be welded on metals of low melting points, such as lead. Gas welding serves excellently for such work as brazing, soldering, general repairs and maintenance, auto bodywork, and the welding of thin sheet metal and lead.
Certain types of welding, such as TIG, MIG, and plasma torch welding, are a combination of gas and electric welding, since they use an electric arc carried through a stream of gas of special composition.