Welding is a type of metal fabrication process where two pieces of metal are joined together through the application of extreme heat. Sometimes, other metals as well as gases are added to speed up the welding process. One of the most common techniques used by welding companies in metal fabrication is gas metal arc welding.
Gas metal arc welding (GMAW), or Metal inert gas (MIG), uses inert gas during the welding process. In a GMAW set-up, a continuous wire electrode is fed through the welding gun as it produces an electric arc to combine the two pieces of metal. An inert gas from a separate source is used to shield the welding site from atmospheric contamination. Below are the various equipment required in a GMAW or MIG welding:
- Welding Gun or Torch: Contains the wire feed and supply of shielding gas; controls the wire feed and flow of electricity
- Wire Feed Unit: Provides the wire metal electrode during the welding operation
- Shielding Gas Source: Supplies the shielding gas, either argon, carbon dioxide or helium, and usually contained in a tank or cylinder
- Power Supply: Provides constant voltage power source; One end is connected to the welding gun while the other end is connected to the workpiece using a clamp
- Ground Clamp: Clips directly on the piece of metal or welding table
Gas metal arc welding can be used in almost any type of metal. The three most common metals welded in a GMAW process are carbon steel, stainless steel, and aluminum.
In GMAW, there are many factors to consider in order to achieve a good-quality weld. They are as follows:
Base Material
The characteristics of the base metal, such as its thickness and whether it is coated, affect the set-up, type of shielding gas, and wire electrode to be used in the process. The base material must also be prepped properly by wiping the surface of the metal with a solvent or degreaser, and then using a cleaning material to remove any surface contaminants and impurities.
Filler Material or Wire Electrode
The composition of the wire electrode should match or have a similar melting temperature with the base material so the alloy will melt easier.
Shielding Gas Mixture
The shielding efficiency of gas mixtures depends on the application and types of material used in the welding process. For carbon steels, a gas mixture of 90% argon and 10% carbon dioxide is ideal, while pure argon works best in welding aluminum.
Welding Pattern
There are four types of welding patterns. The choice of welding pattern determine how smooth and uniform the weld is.
- Steady motion: Most basic welding pattern; the hotter the setting, the better the weld
- Whipping: Ideal for joints using stringer beads or fillet welds
- Circular: Combination of whipping and weaving patterns; works on most joint types
- Weaving: Used in larger or wider joints
Gas metal arc welding is frequently used in many industries, resulting in a high-productivity yet low-cost welding process. Some of the industries where GMAW is typically used include automotive production and maintenance, manufacturing, shipbuilding, and construction. Gas metal arc welding is also used in welding pipe joints, railroad tracks, and underwater welding.