Arc Welding Types
Shielded-Metal Arc Welding
/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 work piece 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.
Gas Metal-Arc Welding
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.
Electroslag Welding
Electroslag Welding (ESW)deposits the weld metal into the weld cavity between the two plates to be joined. This space is enclosed by water cooled copper dams or shoes to prevent molten slag from running off. The weld metal is produced from a filler wire that forms an initial arc with the workpiece until a sufficient pool of liquid metal is formed to use the electrical resistance of the molten slag.
This process requires special equipment used primarily for horizontal welds of very large plates up to 36 inches or more by welding them in one pass as in large machinery and nuclear reactor vessels.
There are also variations of ESW where shielding is provided by an appropriate gas and a continuous arc is used to provide weld metal. These are termed Electro gas Welding or EGW machines.
Fluxed-Core Arc-Welding
[/url]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.
Plasma Arc Cutting
Plasma arc cutting can increase the speed and efficiency of both sheet and plate metal cutting operations. Manufacturers of transportation and agricultural equipment, heavy machinery, aircraft components, air handling equipment, and many other products have discovered its benefits.
Plasma cutters are used in place of traditional sawing, drilling, machining, punching, and cutting. The high-temperature plasma arc cuts through a wide variety of metals at high speeds. Although plasma arc cutting can cut most metals at thicknesses of up to 4 to 6 inches, it provides the greatest economical advantages, speed, and quality on carbon steels under 1 inch thick, and on aluminum and stainless steels under 3 inches thick.
Plasma arc cutting has gained approval in both hand-held and automated cutting operations. Some of the most impressive results are achieved in automated systems. Advances in computer numerical controls (CNC), robots, and other automation techniques have offered manufacturers higher cutting speeds achieved through plasma arc cutting. Improved torch designs and more efficient power supplies have made plasma arc cutting increasingly popular.
New areas of technology in plasma arc cutting systems include non-transferred arc plasma, which allows plastics and other nonconductive materials to be cut. Research on cutting plastics is continuing and at least one commercial process is currently available.
Plasma Arc Cutting Advantages
[/url]Automated plasma arc cutting systems provide several advantages over other cutting methods such as oxyfuel and laser.
Rapid Cutting Speeds:
Plasma arc cutting is faster than oxyfuel for cutting steel up to 2 inches thick and is competitive for greater thicknesses. Plasma cutting achieves speeds greater than those of laser cutting systems for thicknesses over 1/8 inch. CNC controls allow speeds of up to 500 inches per minute (ipm) to be achieved on gauge thicknesses. These fast cutting speeds result in increased production, enabling systems to pay for themselves in as little as 6 months for smaller units.
WideRange of Materials and Thicknesses:
Plasma cutting systems can yield quality cuts on both ferrous and nonferrous metals. Thicknesses from gauge to 3 inches can be cut effectively.
Easy to Use:
Plasma cutting requires only minimal operator training. The torch is easy to operate, and new operators can make excellent cuts almost immediately. Plasma cutting systems are rugged, are well suitable for production environments, and do not require the potentially complicated adjustments associated with laser cutting systems.
Economical:
Plasma cutting is more economical than oxyfuel for thicknesses under 1 inch, and comparable up to about 2 inches. For example, for ½ inch steel, plasma cutting costs are about half those of oxyfuel.
Shielded-Metal Arc Welding
/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 work piece 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.
Gas Metal-Arc Welding
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.
Electroslag Welding
Electroslag Welding (ESW)deposits the weld metal into the weld cavity between the two plates to be joined. This space is enclosed by water cooled copper dams or shoes to prevent molten slag from running off. The weld metal is produced from a filler wire that forms an initial arc with the workpiece until a sufficient pool of liquid metal is formed to use the electrical resistance of the molten slag.
This process requires special equipment used primarily for horizontal welds of very large plates up to 36 inches or more by welding them in one pass as in large machinery and nuclear reactor vessels.
There are also variations of ESW where shielding is provided by an appropriate gas and a continuous arc is used to provide weld metal. These are termed Electro gas Welding or EGW machines.
Fluxed-Core Arc-Welding
[/url]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.
Plasma Arc Cutting
Plasma arc cutting can increase the speed and efficiency of both sheet and plate metal cutting operations. Manufacturers of transportation and agricultural equipment, heavy machinery, aircraft components, air handling equipment, and many other products have discovered its benefits.
Plasma cutters are used in place of traditional sawing, drilling, machining, punching, and cutting. The high-temperature plasma arc cuts through a wide variety of metals at high speeds. Although plasma arc cutting can cut most metals at thicknesses of up to 4 to 6 inches, it provides the greatest economical advantages, speed, and quality on carbon steels under 1 inch thick, and on aluminum and stainless steels under 3 inches thick.
Plasma arc cutting has gained approval in both hand-held and automated cutting operations. Some of the most impressive results are achieved in automated systems. Advances in computer numerical controls (CNC), robots, and other automation techniques have offered manufacturers higher cutting speeds achieved through plasma arc cutting. Improved torch designs and more efficient power supplies have made plasma arc cutting increasingly popular.
New areas of technology in plasma arc cutting systems include non-transferred arc plasma, which allows plastics and other nonconductive materials to be cut. Research on cutting plastics is continuing and at least one commercial process is currently available.
Plasma Arc Cutting Advantages
[/url]Automated plasma arc cutting systems provide several advantages over other cutting methods such as oxyfuel and laser.
Rapid Cutting Speeds:
Plasma arc cutting is faster than oxyfuel for cutting steel up to 2 inches thick and is competitive for greater thicknesses. Plasma cutting achieves speeds greater than those of laser cutting systems for thicknesses over 1/8 inch. CNC controls allow speeds of up to 500 inches per minute (ipm) to be achieved on gauge thicknesses. These fast cutting speeds result in increased production, enabling systems to pay for themselves in as little as 6 months for smaller units.
WideRange of Materials and Thicknesses:
Plasma cutting systems can yield quality cuts on both ferrous and nonferrous metals. Thicknesses from gauge to 3 inches can be cut effectively.
Easy to Use:
Plasma cutting requires only minimal operator training. The torch is easy to operate, and new operators can make excellent cuts almost immediately. Plasma cutting systems are rugged, are well suitable for production environments, and do not require the potentially complicated adjustments associated with laser cutting systems.
Economical:
Plasma cutting is more economical than oxyfuel for thicknesses under 1 inch, and comparable up to about 2 inches. For example, for ½ inch steel, plasma cutting costs are about half those of oxyfuel.
