Carbon arc welding is one of the oldest welding techniques that are still in use today. The process of carbon arc welding uses low voltage, high amp electricity to heat the metal once an arc is formed between a carbon electrode and the piece being welded; if an arc is formed between two carbon electrodes that technique is known as a twin-carbon arc. Because of advancements in the welding field, the technique of carbon arc welding is hardly used, especially among welders who are just learning to weld. However, may older welders who know the technique still use it from time to time.
The technique of single-carbon arc welding uses a direct current power supply which is connected using a straight polarity. This technique was a favorite when welders needed to work with galvanized sheet metal because the heat created when welding could be concentrated on one general area and lessen the amount of distortion that the metal experienced. The process of carbon arc welding requires the welder to use hand pieces that were designed specifically for use with this technique. The hand pieces must be able to handle the higher temperatures produced by the electrodes, and the hand pieces used in an industrial setting are water-cooled to help protect the welder from the significant heat that is produced in this process.
The electrodes that are used in carbon arc welding consisted of baked carbon or pure graphite which was placed inside a copper jacket. During the welding process, the electrode is not consumed as the weld progresses; overtime, however, the electrodes will need to be replaced due to erosion. The average carbon electrode that is used is typically six inches long and can range in diameter from 3/16 to ½ inch in size. The temperatures that are created using carbon arc welding average between 5000 degrees Celsius to 9000 degrees Fahrenheit and are known for creating an extremely bright light. This bright light can be dangerous for the welder if they are not wearing the proper eye protection and clothing.
As with all old technologies, with the advances made in welding and the development of newer techniques, the process of carbon arc welding has become a skill of the past. Although there are still welders working today who are familiar with the technique, it is not a required technique for new welders to learn. If you are interested in learning and trying carbon arc welding, you may want to consult with someone who has been welding for years; they may have the experience necessary to pass the technique on to you.
Reference: http://wiki.answers.com/Q/What_is_Carbon_arc_welding
