MIG and TIG welding both employ an arc of electricity to make welds, but the MIG method uses a continuously feeding spool of wire to burn, melt and fuse the base and parent metals together. The TIG method requires long welding rods and is a more delicate, time-consuming technique. One method or the other will allow a wide range of materials to be welded, from thin sheet metal to heavy structural plates.

Introduction of MIG Welding

MIG welding, also known as Gas Metal Arc Welding (GMAW), was developed in the 1940s for welding aluminum and other non-ferrous metals. Although it could also be used to weld steel, the high cost of the inert gases used in the process meant it was not cost-effective.

In the 1950s, the use of carbon dioxide made welding steel more economical, and MIG welding quickly became popular, primarily for its speed, versatility, and adaptability to robotic automation. Today, MIG welding is the most common industrial welding process.

Aluminum Welding Challenges

Aluminum and its alloys are easily weldable; however, the normal welding characteristics of steel don’t always apply. There are several issues unique to aluminum that need to be considered, including:

1. Aluminum is roughly one-third the weight of steel, melts at less than one-half of steel’s melting point, and has a thermal conductivity about six times that of steel. For efficient welding, the heat for melting aluminum has to be more intense than that required to melt steel.
2. Aluminum has a high electrical conductivity (only one-third less than copper). Because it won’t change color when heated and will appear to be cold, the welder must be careful not to touch hot metal.
3. Aluminum has a thin coating of naturally occurring oxide that prevents corrosion, but has to be removed before welding to avoid fusion due to its high melting point. It’s also very porous and easily traps moisture, oil, grease and other materials. 
4. Aluminum is non-magnetic, so magnetic lifting devices to aid in welding will be ineffective. 

Heat treatable alloys can be heated after welding to restore strength lost during welding. Strength in non-heat treatable alloys can be increased with cold working or strain hardening.

Advantages of MIG Welding

• It’s very versatile and can weld a wide range of metals and alloys
• It offers all-position welding capability 
• Since a flux is not used, there is no slag to be removed, resulting in high quality welds.
• A minimum of weld spatter is produced.
• The continuously fed wire keeps both hands free for welding, improving the welding speed, quality of the weld, and overall control.

Disadvantages of MIG Welding

• MIG welding is most suitable for thin to medium thick metals.
• Cooling rates are faster since the metal is not covered by slag when the weld is completed.
• The use of an inert gas makes this type of welding less portable than arc welding which requires no external source of shielding gas
• Produces a somewhat sloppier and less controlled weld as compared to TIG (Tungsten Inert Gas Welding)

Hydro Extrusion, the world’s leading soft alloy aluminum extruder, provides a comprehensive suite of services for clients in virtually all industrial, commercial and consumer markets. We have extensive experience in joining technologies, including aluminum MIG welding, TIG welding, and Friction Stir welding (FSW), and can satisfy your most challenging requirements.