The use of carbon rods made a sizeable impact in welding’s history when, in 1800, Sir Humphrey Davy created an arc between two carbon rods and then again in 1881 when Nikolay Benardos and Stanisław Olszewski built upon Davy’s discovery to create carbon arc welding (CAW). The use of carbon rods was essential to the kickoff of welding, but it was much later when they were applied as a cutting process.

Carbon arc cutting originated in the 1940s. The process was used to cut away rivets in the overhead and vertical positions in hopes that gravity would then assist with dropping the molten material into place. This was a time-consuming and erratic process, though. Not only were the molten dross or sparks unpredictable, but the rivets would not always fall away as planned; instead, sometimes they would reweld themselves back in place (The History of Welding, 2020).

In 1948, Myron Stepath added compressed air to the process (Arcair, 2010). The streams of high-pressurized compressed air act as a blower to push the molten dross, sparks, and material away from the cutting area. This not only was more efficient, but it also allowed the workers to increase their speed and use the process in flat positions as well. The process then became known as air arc cutting (AAC). AAC required two workers: one to operate the carbon arc and the other to operate the compressed air needed to blow away the molten metal.

The process was then refined even further in 1956 with the development of the electrode holder we use today (Arcair, n.d.). This development brought the compressed air stream into an easy-to-use, handheld electrode holder, eliminating the need for two people for the job. CAC-A was born.

Basics of the Process

A carbon arc is an electric arc process where the heat generated from the arc of a carbon electrode melts the base metal it comes into contact with. CAW is one of the oldest versions of welding, and had been called atomic hydrogen carbon arc welding, or AHW for short (Atomic Hydrogen Welding, 2023). These days CAW is largely obsolete. However, its use as cutting technique—CAC, which uses carbon electrodes to cut and gouge parent material—is still very popular in fabrication, welding, and thermal cutting industries today.

CAC is used to cut away unwanted material by means of a carbon-coated consumable rod, or electrode, held in the jaws of a piece of equipment called an electrode holder that looks very similar to the one used in shielded metal arc welding (SMAW). It’s important to know the key differences between their respective equipment and processes, though. The biggest is that unlike welding where we are adding metal, CAC-A removes metal, welds, and cracks and helps bevel grooves in fit up operations.

The bottom or lower jaw of the electrode holder used in CAC has a head that rotates to ensure accuracy, and it is outfitted with several holes for the compressed air to pass through. There is an air valve on the handle to turn the airflow on or off. When positioned correctly and with the right air pressure, the compressed air blasts the molten metal away from the site directly under the electrode.

No shielding gas is used or needed for CAC-A. As the carbon rod is consumed it produces both carbon monoxide and carbon dioxide gas, however these are blasted away by the airstream. Because this process uses carbon electrodes, carbon deposits are left behind on the surface metal. It is important to clean the surface with a grinder after you are done cutting to avoid brittleness and cracking should the area need to be rewelded, or back-welded.

Unlike oxyacetylene cutting (discussed in Chapter 12), which is only effective on metals that can be oxidized, it is not necessary that the carbon electrode react to the base metal for the CAC process, allowing for more versatility. Stainless steel, carbon steel, titanium, copper alloys, nickel alloys, and aluminum alloys are just a few of the materials an individual may use with the CAC-A process

CAC can be used in all cutting positions. The process can be done manually or, when connected to a carriage or machine that controls the speed and movements, semi-automatically. The cutting process requires a constant current  power source capable of an operating voltage of at least 28 volts or higher. CAC can be operated with alternating current or direct current electrode positive (DCEP), however direct current electrode negative (DCEN) should be avoided, as the arc is too unstable.

Uses of CAC-A in Industry Today

• Boilermakers
• Railway
• Steel mills
• Steel fabrication
• Construction
• Chemical and petroleum industry
• Casting finishing
• Mining industry
• Foundries
• Lumber industry
• Military