What Is Carbon Arc Welding?- Equipment, And Working

What is Carbon Arc Welding?

Carbon arc welding (CAW) produces heat by an electric arc struck between a non-consumable carbon (graphite) electrode and the metal workpiece. The concept is simply using a carbon electrode to create the arc that is the heat source used to join the metals.

CAW was the first electrically driven, arc welding process, whereas CAW has seen very few if any applications in present day operations.

CAW has since been rendered nearly obsolete by new techniques of which the latest is twin-carbon-arc welding as well as some new variations of the technique beyond that.

The basic principle is still the same: joining separate pieces of metal by forming a good metallurgical bond. For instance, in welding the arc exceeds 3,000 °C which generates the appropriate heat to fuse the metals together creating a good connection.

The History Behind

Carbon arc welding fundamentally relies on the formation of an electrical arc. This activity finds its foundation as early as 1800 when Sir Humphry Davy discovered the electric arc.

However, it was not until almost 100 years later when Nikolay Benardos and Stanislaw Olszewski developed the carbon arc welding (CAW) process. It was correctly named Elektrogefest at the time.

Equipment

• Electrode: Typically, the diameter of electrodes utilized in this process will range from 3 mm to 22 mm.
• Power Source: The primary power source in the CAW process consists of direct current welding machines. Depending on the specific configuration, the machines may be of the rotating type or rectifier-based.
• Electrode Holder: It should be noted, the traditional electrode holder is not able to be utilized in the case of CAW. The traditional electrode holder, with the high temperatures required for this process, is just not able to withstand the process so the holder must be specifically manufactured.

Working Of Carbon Arc Welding

The American Welding Society defines carbon arc welding as a welding process in which the heat for the process is obtained from an arc established between carbon electrodes and the base metal. In carbon arc welding, the heat from the arc melts the parent metal (base metal) at the targeted area.

When the molten pool of metal cools and solidifies, it produces the weld at the desired location. Although the electrical arc produces heat and melts the parent metal, it does not mean the size of the carbon electrode is fixed. The electrode can be changed according to the amount of current being used.

There are a few differences to carbon arc welding, and one example is twin carbon arc welding, or TCAW. Twin carbon arc welding uses two operated carbon electrodes, and TCAW works slightly different.

TCAW allows one electrode to move, and it is designed so that one electrode can contact the other electrode to create the started arc.

In TCAW, it is using alternating current, and it is important during TCAW to burn both electrodes at an equal rate while welding, so that both electrodes are consumed equally throughout the process.

Advantages of Carbon Arc Welding

• Heat production during welding can be easily modified through the control of arc length.
• It is relatively clean, simple and also less expensive compared to other welding processes.
• Carbon arc welding is more rapid than other welding processes making it more useful for projects of a bigger scale.
• Carbon arc welding produces less slag than other welding processes which results in easier clean welds.
• Carbon arc welding produces less warping and distortion compared to other welding processes.
• Ferrous and non-ferrous metals can both be welded using carbon arc welding.
• Carbon arc welding can be controlled using electronic controllers which allow for automatic processes.
• As a heat source, carbon arc welding is also the best for soldering, brazing and braze welding, etc.

Disadvantages of Carbon Arc Welding

• When ferrous metals are welded, there is a possibility to burn some of the carbon at high temperatures and deposit it in the weld, which can lead to hard and brittle weld deposits.
• In the absence of sufficient electrode geometry, arc blow can occur leading to poor, and potential blow hole, welds.
• If filler metal is required, a separate filler rod must be used.
• The current needed to achieve welding temperature is close to double the current in metal arc welding.
• Carbon arc welding can be successfully and cheaply done with dc supply.

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