What Is Carbon Arc Welding?- Equipment, And Working

What is Carbon Arc Welding?

Carbon arc welding (CAW) operates by generating intense heat through an electric arc struck between a non-consumable carbon (graphite) electrode and the metal workpiece. The fundamental mechanism involves using a carbon electrode to create the arc, which serves as the primary heat source for joining the metals.

Historically, CAW was the pioneering method in the field of arc welding, although its use has significantly declined in modern practice. The process has largely been superseded by techniques such as twin-carbon-arc welding and several newer variations.

The essential goal remains unchanged: to join separate pieces of metal by forming a strong metallurgical bond. During welding, the arc reaches temperatures exceeding 3,000 °C, providing the necessary heat for the metals to fuse together and form a durable connection.

The History Behind

Carbon arc welding relies fundamentally on the creation of an electric arc. The origins of this technique can be traced back to 1800, when Sir Humphry Davy first identified the phenomenon of the electric arc. Nearly a century later, in 1881, Nikolay Benardos and Stanislaw Olszewski introduced the carbon arc welding (CAW) process. At the time, it was referred to as Elektrogefest.

Equipment

• Electrode: In this process, the electrodes typically range in diameter from 3 mm to 22 mm.
• Power Source: For the CAW process, direct current welding machines serve as the primary power source. These machines may be of the rotating type or utilize rectifiers, depending on the specific setup.
• Electrode Holder: It’s worth noting that the conventional electrode holder isn’t suitable for CAW. Given the exceptionally high temperatures involved, traditional holders simply cannot withstand the demands of this process, so specialized holders are required.

Working Of Carbon Arc Welding

When an electric arc forms between the electrode and the base metal, the resulting heat is enough to melt the parent metal at the targeted spot. Once this molten pool cools and solidifies, it creates the weld exactly where it’s needed. The size of the electrode isn’t fixed—you can adjust it based on how much current is being used during the process.

There’s a specific variant of carbon arc welding known as twin carbon arc welding, or TCAW, which operates a bit differently from the standard approach. In TCAW, a unique electrode setup is required. The process is designed so that one of the carbon electrodes remains movable, allowing it to make contact with the other electrode and initiate the arc.

TCAW specifically uses alternating current. It’s also important to ensure both electrodes are consumed at the same rate throughout the operation, maintaining a balanced burn-off for consistent welding performance.

Advantages of Carbon Arc Welding

• The heat developed during the welding can be easily controlled by adjusting the length of the arc.
• It is quite clean, simple, and less expensive when compared to other welding processes.
• Carbon arc welding is faster than other welding processes, making it ideal for large projects.
• Carbon arc welding produces less slag than other welding processes, making it easier to produce a clean weld.
• Carbon arc welding is less likely to cause warping and distortion than other welding processes.
• Both the ferrous and non-ferrous metals can be welded.
• The carbon arc welding process can be done automatically using electronic controllers.
• For soldering, brazing and braze welding, etc., carbon arc welding is the best method of heat source.

Disadvantages of Carbon Arc Welding

• In the case of ferrous metal, there is a chance of disintegrating the carbon at high temperature and transferring to the weld, which causes weld deposit to be harder and brittle.
• In the absence of proper electrode geometry, arc blow results which give poor welds with blow holes.
• A separate filler rod must be used if any filler metal is required.
• The current required to attain welding temperature is almost double the current required in metal arc welding.
• Carbon arc welding can be efficiently and economically done with dc supply.

FAQs