Welding is a method of bonding two pieces of metal together. In many cases, this bond can be stronger than the base material. The process of fusing two separate pieces of metal requires the base metal to melt and flow together. Old methods would use a blowtorch to heat metal until the base pieces reached melting temperature. New methods use electric arcs to generate the required heat. An electrode—consumable and charged positively or negatively depending on the character of the weld—is passed to a workpiece. There are many methods to achieve metal fusion via welding and choosing the right method is crucial. Here are the different welding methods and their applications:
SAW—Submerged Arc Welding
SAW involves welding a joint using an electric arc smothered under a bed of flux. This process, mostly automated, uses a slowly fed filler wire fed along the joint beneath the flux. High quality welds are yielded thanks to the flux coating the arc and wire; the risk of splatter is negated by the great presence of flux. SAW applications include:
- Heavy plate fabrication
- Pressure vessels and tanks, sub-assemblies, nuclear reactors
GMAW—Gas Metal Arc Welding
GMAW is more commonly known as MIG Welding. MIG stands for Metal Inert Gas. A consumable wire is fed automatically through a gun, while argon gas simultaneously acts as a shielding agent. This type of welding is used in:
- Repairs and rebuilding
- Pipes
GTAW—Gas Tungsten Arc Welding
GTAW is more commonly known as TIG Welding. The most precise and time consuming method, TIG welders feed wire by hand into an arc generated by a non-consumable tungsten electrode housed in an argon dispensing gun, like MIG. The tungsten allow electrode does not melt under high heat, which facilitates the precision of a hand-fed wire. Due to the nature of hand-feeding, this method requires a high level of skill and is applied only to special circumstances. Applications of GTAW include:
- Stainless steel, aluminum, magnesium, copper alloy products
- Aerospace industry
- Piping applications
SMAW—Shielded Metal Arc Welding
SMAW, more commonly known as stick welding, is the most widely used method. A consumable electrode in the form of a stick is covered in flux to create an arc and melt filler between workpieces, ultimately fusing the two together. Applications for this type of welding include:
- Construction
- Pressure vessels, tanks, boilers, ships
FCAW—Flux Core Welding
FCAW is a variation to MIG welding. This type of welding is a wire fed process, using a different electrode than MIG. Of all manual welding processes, FCAW is the most productive process and gives welders the ability to perform a single pass on thick steel plate, penetrating both sides. The main application of FCAW is:
- Ship building
PAW—Plasma Arc Welding
PAW is a process using plasma gas, heated to extremely high temperatures and then ionized to become electrically conductive. The plasma transfers an electric arc to the work piece, melting and fusing metals together. PAW provides a method for welding thin sheet and fine wires, without the harshness of a TIG arc. The arc and tooling are close to the workpiece, reducing arc wander. Applications of PAW include:
- Small components
- Pressure and electrical sensors, micro switches, valves, etc.
HLAW—Hybrid Laser Arc Welding
HLAW is an automated welding process, using a laser guided robot. HLAW removes many steps from traditional welding; a need for flux is eliminated, as is the need for weld preparation. An HLAW machine can weld 300 to 400 percent faster than traditional SAW welding. The speed and precision of the weld lowers deformation risks, as the heat-affected-zone is significantly smaller than other methods. HLAW applications include:
- Long components
- Crane Booms
- Bridge decks, Beams, trusses, pilings, etc.
Each welding method has its advantages and disadvantages. The applications of many of the methods overlap—a project involving welding has options and choices to be made. Ultimately, the designers and engineers of projects must weigh the benefits of possible methods and decide which method best suits the application.
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