What is Flux-Cored Arc Welding (FCAW)?
Flux-cored arc welding is another type of arc welding process that uses consumable electrodes that contain flux around it. This process is commonly referred to as semi-automatic or automatic arc welding.
The coalescence of metal is produced by heating with an arc between a continuously fed electrode and the base metals. The shielding is obtained by the flux in the electrode.
An externally supplied inert gas may or may not be the source of the additional shield. That is, shielding gas is supplied from an external source, such as a gas cylinder or a shield flux coated around the electrode, which is deposited when it is melted.
During the welding process, the flux melts together with the electrode, providing shielding gas to the entire weld area. It protects the weld pool from the atmosphere.
Flux-cored arc welding utilizes a tubular electrode filled with flux for self-shielding, protecting the weld from atmospheric contamination.
It offers flexibility in indoor and outdoor settings, making it a popular choice in industries like shipbuilding and construction due to its higher deposition rates and deeper penetration.
Applications of FCAW
FCAW welding is a versatile technique used in various industries, including general repairs, shipbuilding, and manufacturing. Its portability and ability to endure harsh outdoor conditions make it a preferred choice for welding ferrous metals.
In the pipeline manufacturing industry, FCAW welding produces welds with minimal porosity, ensuring unparalleled strength and durability.
The manufacturing industry can automate the process using robots, resulting in precise and consistent welding seams. Shipbuilding uses the continuously fed tubular electrode for efficient operation, as it allows for constant change of welding positions.
Underwater welding, a wet welding procedure, offers protection from the protective gas layer produced by flux-cored electrodes but requires skill and training due to the high hazards.
Related: How Does Metal Inert Gas (MIG) Welding Works?
FCAW Parts and Equipment
The parts of a flux-cored arc welding machine include a power source, wire feeder, welding gun, and shielding gas.
Power Source
The welding method for ferrous materials typically uses a direct current (DC) power source, offering better penetration and stability. DC positive polarity (DCEP) is the most common setting, providing deep penetration and safe filler metal deposit.
For thinner metals, we use DC negative polarity (DCEN), and we can use self-shielding flux electrodes with both positive and negative polarities.
Wire Feeder
The tubular electrode in the welding receives constant power from a wire feed motor. This equipment can manage the supply of wire from the spool to the welding flame by adjusting the wire feed speed.
Welding Gun
Air-cooled guns are suitable for welding currents under 500 amperes, cooled by ambient air. They are lighter, less expensive, and produce high-quality weld beads.
We recommend water-cooled guns for welding currents larger than 600 amperes, as they can withstand high temperatures for extended periods. Water-cooled guns rapidly lower temperatures by allowing water to flow around the contact tube and nozzle.
Shielding Gas
Dual-shield welding shielding gas, such as carbon dioxide and argon, is used to protect the weld pool from the atmosphere, reducing the risk of porosity and brittleness. FCAW welders prefer carbon dioxide because of its low cost and deep penetration.
A combination of argon and carbon dioxide is used to generate less spatter, with a filler metal resulting in higher strength properties. Sometimes, we mix pure argon with 1-2% oxygen to weld metals that can corrode with CO2, thereby promoting less spatter.
Electrode and Wire
The welding process utilizes different types of electrodes, such as gas-shielded all-position, flat-position, and self-shielded electrodes. All position electrodes measure less than 1/16 inches and provide control; however, they are unsuitable for use with highly contaminated base metal.
Flat position electrodes exceed 1/16 inches in size and provide rapid deposition rates, making them appropriate for thicker metals.
Self-shielded electrodes are optimal for outdoor applications, including construction and fabrication, and are effective for welding galvanized steel or using hard-to-reach gas cylinders.
Related: What is Arc Stud Welding? Diagram & How it Works
Diagram of Flux Cored Arc Welding
How Does Flux-Cored Arc Welding Work?
The working of flux-cored arc welding (FCAW) is less complex and can be easily understood. Unlike other arc welding processes that use AC or DC power supplies, FCAW supplies power only from a DC electric arc to the welding gun.
The arc is produced when the gun is struck between the continuously fed consumable filler wire and the workpiece. It creates the weld pool and bonds when the pool solidifies.
The Flux-Cored Arc Welding (FCAW) process is a method used to create a weld using heat from the arc generated between the tubular electrode and the workpiece.
The electrode, hollow with a flux core inside, acts as a shielding agent, protecting the weld from atmospheric contamination. There are two main options for performing FCAW: self-shielded (FCAW-S) and dual-shielded (FCAW-G).
The choice of welding process depends on factors like portability, desired mechanical properties, and base metal. Robots can perform FCAW semi-automatically or fully automatically.
Parameters for optimum results include wire feed speed, contact tip distance, travel speed, and work angle.
Related: What is Arc Welding? Diagram, Types & How it Works
Differences Between FCAW and GMAW
FCAW welding uses a flux-cored electrode to emit a protective shielding layer, preventing contaminants from entering the weld pool.
This process is ideal for ferrous metals and requires minimal pre-cleaning. Dual-shielded FCAW offers consistent mechanical properties and higher deposition rates.
GMAW (MIG/MAG welding) uses a solid wire electrode and external shielding gas to prevent contamination, leaving more weld spatter and less penetration.
GMAW has a larger electrode wire than FCAW, but the main difference lies in shielding the weld zone using electrodes and shielding gases. Both types offer versatility in welding various metals.
Advantages and Disadvantages of FCAW
Flux-cored arc welding (FCAW) is a versatile and efficient welding process that offers higher penetration than MIG/MAG welding, the ability to weld ferrous metals, and more portability than MIG welding.
It is easier to learn than stick and TIG welding and uses the same machine as FCAW.
However, it has disadvantages such as slag cleanup, poorer weld beads than TIG welds, higher costs for flux tubular electrodes, and potential for trapping gases in the weld zone.
FCAW is slowly replacing SMAW in manufacturing and construction due to automation, allowing robots to perform pin-point welding at any position.