Fluxed-Core Arc-Welding

Fluxed-Core Arc-Welding (FCAW) uses a tubular electrode filled with flux that is much less brittle than the coatings on SMAW electrodes while preserving most of its potential alloying benefits.

The emissive fluxes used shield the weld arc from surrounding air, or shielding gases are used and nonemissive fluxes are employed. The higher weld-metal deposition rate of FCAW over GMAW (Gas Metal Arc Welding) has led to its popularity in joining relatively heavy sections of 1" or thicker.

Another major advantage of FCAW is the ease with which specific weld-metal alloy chemistries can be developed. The process is also easily automated, especially with the new robotic systems.

Gas Metal-Arc Welding (GMAW), also called Metal Inert Gas (MIG) welding, shields the weld zone with an external gas such as argon, helium, carbon dioxide, or gas mixtures. Deoxidizers present in the electrode can completely prevent oxidation in the weld puddle, making multiple weld layers possible at the joint.

GMAW is a relatively simple, versatile, and economical welding apparatus to use. This is due to the factor of 2 welding productivity over SMAW processes. In addition, the temperatures involved in GMAW are relatively low and are therefore suitable for thin sheet and sections less than ¼ inch.

GMAW may be easily automated, and lends itself readily to robotic methods. It has virtually replaced SMAW in present-day welding operations in manufacturing plants.

Click to view larger JPEG. Gas Tungsten-Arc Welding (GTAW), also known as Tungsten Inert Gas or TIG welding, uses tungsten electrodes as one pole of the arc to generate the heat required. The gas is usually argon, helium, or a mixture of the two. A filler wire provides the molten material if necessary.

The GTAW process is especially suited to thin materials producing welds of excellent quality and surface finish. Filler wire is usually selected to be similar in composition to the materials being welded.

Atomic Hydrogen Welding (AHW) is similar and uses an arc between two tungsten or carbon electrodes in a shielding atmosphere of hydrogen. Therefore, the work piece is not part of the electrical circuit.

Shielded-Metal Arc Welding (SMAW) is one of the oldest, simplest, and most versatile arc welding processes. The arc is generated by touching the tip of a coated electrode to the workpiece and withdrawing it quickly to an appropriate distance to maintain the arc. The heat generated melts a portion of the electrode tip, its coating, and the base metal in the immediate area. The weld forms out of the alloy of these materials as they solidify in the weld area. Slag formed to protect the weld against forming oxides, nitrides, and inclusions must be removed after each pass to ensure a good weld.

The SMAW process has the advantage of being relatively simple, only requiring a power supply, power cables, and electrode holder. It is commonly used in construction, shipbuilding, and pipeline work, especially in remote locations.