- Shielding gas
Shielding gases are inert or semi-
inert gas es that are commonly used in severalwelding processes, most notablygas metal arc welding andgas tungsten arc welding . Their purpose is to protect the weld area from atmospheric gases, such asoxygen ,nitrogen ,carbon dioxide , andwater vapour . Depending on the materials being welded, these atmospheric gases can reduce the quality of the weld or make the welding process more difficult to use. Other arc welding processes use other methods of protecting the weld from the atmosphere as well –shielded metal arc welding , for example, uses anelectrode covered in a flux that produces carbon dioxide when consumed, a semi-inert gas that is an acceptable shielding gas for welding steel.Common shielding gases
Shielding gases fall into two categories—inert or semi-inert. Only two of the
noble gases ,helium andargon , are cost effective enough to be used in welding. These inert gases are used in gas tungsten arc welding, and also in gas metal arc welding for the welding of non-ferrous materials. Semi-inert shielding gases, or active shield gases, includecarbon dioxide ,oxygen ,nitrogen , andhydrogen . Most of these gases, in large quantities, would damage the weld, but when used in small, controlled quantities, can improve weld characteristics.Applications
The applications of shielding gases are limited primarily by the cost of the gas, the cost of the equipment, and by the location of the welding. Some shielding gases, like argon, are expensive, limiting its use. The equipment used for the delivery of the gas is also an added cost, and as a result, processes like
shielded metal arc welding , which require less expensive equipment, might be preferred in certain situations. Finally, because atmospheric movements can cause the dispersion of the shielding gas around the weld, welding processes that require shielding gases are often only done indoors, where the environment is stable and atmospheric gases can be effectively prevented from entering the weld area.ee also
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Forming gas References
*Cary, Howard B. and Scott C. Helzer (
2005 ). Modern Welding Technology. Upper Saddle River,New Jersey : Pearson Education. ISBN 0-13-113029-3.
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