All arc welding processes have a few basic requirements for their operation. They must have a safe voltage available that is sufficient for the operator to get the arc started and be maintained. They also require sufficient amperage to provide the heat for melting of the parent metal and filler material.
Arc welding processes have been a popular and widely applied method of welding for many years. They offer sound and reliable weld, simple operation and low capital cost.
Arc welding process overview
There are a lot of arc welding processes used in the metal fabrication and welding industries. Some of these are commonly used and others are used in specialist applications. This section introduces some of the most commonly used arc welding processes; which are:
- Manual metal arc welding (MMAW)
- Gas metal arc welding (GMAW)
- Flux cored arc welding (FCAW)
- Submerged arc welding (SAW)
- Gas tungsten arc welding (GTAW)
Manual metal arc welding (MMAW)
MMAW is a welding process that creates an electric arc between a hand held, flux-coated, consumable filler wire and the work piece. The arc heat melts the parent metal and filler wire. The flux coating breaks down in the arc to produce a gaseous shield that excludes atmospheric gases from the weld zone. The flux coating also provides a de-oxidising action and forms a slag on the cooling weld. The MMAW welding process needs a suitable and constant current power source (AC
or DC), a handpiece, a work clamp, leads and flux-covered consumable electrodes.
MMAW process
MMAW equipment is cheap and simple to use and people with very little training and practice are able to use the MMAW process to make reliable welds. A skilled operator can use the MMAW process to weld practically any material in virtually any situation.
Typical uses for the MMAW process include:
- light/heavy/fabrication
- general engineering
- site work
- repairs.
Gas metal arc welding (GMAW)
GMAW is a welding process that creates an electric arc between an automatically fed wire electrode and the work piece. The arc heat melts the parent metal and filler wire. A supply of shielding gas that excludes atmospheric gases from the weld zone is introduced around the arc.
The GMAW welding process needs a suitable and constant voltage power source (DC), a wire feed unit, consumable wire electrodes, a shielding gas supply, a welding gun, a work clamp and leads.
GMAW equipment is not as cheap as MMAW and requires some skill to set up properly. A good operator can use the GMAW process to weld most materials in most welding positions. Typical uses for the GMAW process include:
- light/heavy
- fabrication
- general engineering
- most materials and thicknesses.
Flux-cored arc welding (FCAW)
FCAW is a welding process that creates an electric arc between an automatically fed, hollow wire filled with flux and the work piece. The arc heat melts the parent metal, filler wire and flux. The flux may also add additional material or elements and breaks down in the arc to produce a gaseous shield that excludes atmospheric gases from the weld zone. An optional supply of shielding gas may be introduced around the arc.
The FCAW welding process needs a suitable and constant voltage power source (DC), wire feed unit, consumable flux-filled electrodes, an optional shielding gas supply, a welding gun, a work clamp and leads.
FCAW equipment is generally more robust than GMAW plant and requires some skill to set up properly. The process may be self shielding or gas shielded.
Typical uses for the FCAW process include:
- heavy fabrication
- general engineering.
FCAW has a better deposition rate and fusion than GMAW.
Submerged arc welding (SAW)
SAW is a welding process that creates an electric arc between an automatically fed wire electrode and the work piece. The arc heat melts the parent metal and filler wire. A supply of flux material is introduced around the arc to contribute to the welding operation, exclude atmospheric gases from the weld zone and form a slag over the cooling weld. The SAW welding process needs a heavy duty power source (DC), a wire feed unit, wire electrodes, flux and a flux delivery system, a power head unit, a welding gun, a work clamp and leads.
SAW equipment is heavy and specialised and generally produces high quality welds on steel products. Typical uses for the SAW process include:
• heavy/fabrication
• flat butt and fillet welds only
Gas tungsten arc welding (GTAW)
GTAW is a welding process that creates an electric arc between a non-consumable tungsten electrode and the work piece. The arc heat melts the parent metal. A supply of inert shielding that excludes atmospheric gases from the weld zone gas is introduced around the arc. Filler wire may be introduced into the weld area. The GTAW welding process needs a suitable and constant current power source (AC or DC), tungsten electrodes, an inert shielding gas supply, a welding torch, a work clamp and leads
The GTAW equipment process requires some skill to set up properly and a good operator can produce high quality welds on nearly all materials. Typical uses for the GTAW process include: light fabrication general engineering root runs, pipe work.
GTAW welds most materials and thicknesses (carbon steel, aluminium, stainless steel etc). There are other welding processes used in the metal fabrication industry that are not covered in this text. These are:
- electric resistance welding (ERW)
- electroslag welding (ESW)
- laser welding (LW)
- fuel gas welding (FGW).
Fuel gas welding is covered in greater depth in gas welding theory