Carbon Arc Welding And Its Process

In this method, a rod of carbon is used as negative electrode and the work being welded as a positive. The arc produced between these two electrodes heats the metal to the melting temperature. This is about 3200*C on the negative electrode, and 3900*C on the positive electrode. The reason to use carbon rod as negative electrode is that less heat will be generated at the electrode tip than that the workpiece , and carbon from the electrode will not fuse and mix up with the job. If this so happens the resultant weld will be rich in carbon, and consequently very much brittle and unsound. In carbon - Arc welding, DC is always used. The use of ac is not recommended because no fixed polarity can be maintained.

The process is best applied to the joints which need only to be melted without the addition of filler metal (e.g., flange or edge joints) but fuller metal, if needed, may be added in the form of the welding rod as in oxy-acetylene welding. Some protection for the molten weld metal may be provided by using a long arc which produces a carbon-monoxide gas envelope. In addition, a flux may be used, and welding rods usually incorporate a deoxidizer such as a silicon or phosphorous. This process is used is used for welding sheet steel, copper alloys, brass, bronze, and aluminum.

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Mechinopedia For Mechanical Engineers

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