20 FCAW Overview

Flux cored arc welding (FCAW) is an arc welding process that uses a tubular electrode with flux in its core. FCAW is capable of high weld metal deposition rates and deep penetration. FCAW is very similar to GMAW with respect to operation and the type of equipment used. In FCAW, weld metal is transferred as in GMAW globular or spray transfer.

The flux cored arc welding process was developed in the 1950s with the development of an electrode that contained a core of powdered flux material. However, even with the flux cored electrode, an external shielding gas was required. In 1959, a flux cored electrode was developed that did not require an external shielding gas. Shielding gas could be generated solely by the flux contained in the core of the electrode as it was being consumed during the welding process. This reduced the cost of the welding process by eliminating the need for additional shielding gas and its accompanying equipment.

Types of FCAW

• Self-Shielded FCAW (FCAW-S): In this process, the electrode’s flux generates shielding gases when it decomposes during welding. This eliminates the need for external shielding gas and is commonly used for outdoor and field applications. FCAW-S is also called Innershield in the field, although Innershield specifically refers to a FCAW process developed by Lincoln.
• Gas-Shielded FCAW (FCAW-G): This process uses an external shielding gas, usually a mix of argon and carbon dioxide, to protect the weld pool from atmospheric contamination. FCAW-G typically provides better control over the welding process and produces cleaner welds.

Both FCAW-S and FCAW-G produce a slag coating over the weld to protect it from the atmosphere, although this slag is easily removed.

Welding Equipment

Equipment for FCAW is similar to that used for GMAW. The required equipment includes a welding machine, a welding gun cable and gun assembly, a wire feeder with knurled drive rolls, flux cored electrode wire, and workpiece lead with a workpiece connection. Additionally, for FCAW-G, shielding gas and a shielding gas supply system are required.

• FCAW-S: Requires a welding machine capable of providing sufficient amperage to melt the electrode and produce the desired weld size.
• FCAW-G: Requires a welding machine with both voltage and wire feed speed control to regulate the arc and achieve proper penetration.

Electrodes and Flux

• FCAW-S: The electrode’s flux generates shielding gases as it burns, eliminating the need for external shielding gas. The flux composition influences the welding characteristics and final weld quality.
• FCAW-G: The electrode’s flux generates some shielding gas, but an additional external shielding gas is used to provide better arc stability and protect the weld pool.

Shielding Gas

• FCAW-G uses a mix of shielding gases, usually argon and carbon dioxide, to protect the weld pool. The gas composition affects the arc stability and weld quality.