What is MIG Welding?

MIG welding, sometimes referred to as gas metal arc welding (GMAW), is a semi-automated welding technique that joins metals with an electric arc. An arc forms between the constantly supplied base metal and the welding wire. An arc's heat liquefies the electrode and joint components, fusing them to form a strong, long-lasting connection.

The term "gas" originated from the electrode's distinctive characteristics. MIG welding wire is "bare," much like TIG welding wire, which requires protection from an external shielding gas. Shielding gases, such as argon, protect the weld pool from ambient gas interactions, which can cause a variety of weld faults.

How Does MIG Welding Work?

MIG welding, also known as gas metal arc welding (GMAW), is a welding process that uses an electrical arc to melt and join metal pieces together.

When you pull the trigger on your MIG torch to begin welding, an arc forms when the electricity cuts off the supply to the gun, the metal surface, and the welder. Concurrently, the gun supplies shielding gas, and the wire feed mechanism begins feeding the MIG wire at the pre-set wire speed. In this process, a wire electrode is fed through a welding gun and melted by an electrical arc, resulting in a pool of molten metal that cools to form a joint.

The MIG Welding Process

The MIG welding process is a powerful technique for creating structurally efficient and integrity-preserving joints. To begin, it's essential to follow a pre-weld clean-up process, as MIG electrodes are not resistant to rust, dirt, or oil, so starting with a contaminant-free area is crucial.

Here are the top tips for a proper MIG welding process:

Pre-weld clean-up

Proper metal preparation is essential for MIG welding, as it is not known for its ability to burn through dirt, rust, paint, or mill scale. Contaminants can compromise the weld's integrity, cause defects, and release toxic fumes, posing health risks.

Before welding, clean the metal surface using an old rag or a wire brush, sanding paper, a grinder, or chemicals. A clean surface ensures a sound weld.

After cleaning, align the pieces and clamp them to the welding table to ensure even gaps throughout the weld joint, ensuring consistent results and penetration throughout the weld.

MIG welding position and angle

A good MIG weld necessitates precise gun positioning in order to prevent filler from drooping or rolling over the weld joint's edge. You can perform MIG welding in overhead, vertical, horizontal, and flat orientations. Depending on the type of weld and metal used, you must also consider the work and travel angles.

Travel angle: The angle with respect to the cannon when it is in a perpendicular position. In all cases, a travel angle of 5 to 15 degrees is required for normal welding conditions. (Travel angles greater than 20 to 25 degrees may result in less penetration, more spatter, and overall arc instability.)

Work angle: This is a term that describes how the gun is positioned in relation to the welding joint's angle; it changes depending on the welding position and joint type.

Modes of metal transfer

The process of processing the filler metal (electrode) through the welding arc and into the weld puddle is known as metal transfer.

Short-Circuit Welding Techniques

• Uses the lowest current and voltage ranges, resulting in a low weld heat input.
• Suitable for out-of-position welding and joining thin sections.
• Susceptible to incomplete fusion defects, especially during multipass welds.

Globular transfer welding

• Requires higher current and voltage levels than short-circuiting.
• Characterized by large, irregular drops of molten metal.
• Limited to flat-position welding due to gravity's critical role in drop detachment and transfer.

Spray Welding

• Increases welding current and voltage for a high deposition rate.
• Ideal for joining thicker materials.
• Offers strong, aesthetically pleasing welds with minimal spatter.

Pulsed Mode Welding

• Ideal for welding thinner materials with lower heat input.
• Controlled droplet form while the pulse mode creates spatter-free welds.

What Are the Typical Materials Used in MIG Welding?

You can use MIG welding to weld a variety of materials. However, MIG welding is more common for some materials than others. Here are the four most common metals welded with a MIG welder:

Copper: Pipes and electric applications typically use copper, a soft, flexible steel. MIG welding is the recommended technique, but the greater warmth required than steel makes it simpler and more practical.

Light-weight aluminum: Lightweight aluminum, a soft, silvery, non-ferrous steel, requires 100% pure argon gas for welding. However, the metal pool's rapid thawing can test this procedure.

Steels: Steels are alloys made mostly of iron and carbon, with sulfur and phosphorus commonly present. We advise using 75% argon and 25% co2 when welding steel, as 100% argon gas reduces weld ductility.

Nickel: Nickel alloys, made up of nickel, chromium, iron, molybdenum, and/or copper, are usually bonded with 100% argon gas; however, approximately 40% helium can be used for boosted power.

Advantages and Disadvantages of MIG Welding

Compared to other welding designs, it can lead to much shorter manufacturing times and, consequently, lower prices. MIG welding offers several advantages that make it a popular choice for both industrial and hobbyist welders. 

MIG Welding Advantages

• High productivity is possible with MIG welding since the wire is constantly supplied during the operation.
• MIG welding creates superior welds more quickly than TIG (tungsten inert gas) or SMAW (shielded metal arc welding).
• MIG welding is a flexible procedure that makes it simple to join different metals and alloys, such as iron, copper, nickel, and aluminum. 
• This method can combine different metals. 
• The metal is transferred across the electric arc while the arc is shielded by the shielding gas. Consequently, only a small amount of alloying elements are lost. 
• There is some small weld splatter from the welding process, but it is easily cleaned off.

MIG Welding Disadvantages

• The high heat input and fluidity of the weld puddle make MIG welding unsuitable for overhead and vertical welding positions. 
• MIG welder equipment is complex in comparison to equipment used for shielded metal-arc welding. 

MIG Welding Application

MIG welding is a flexible method. This makes the procedure appropriate for welding a wide variety of structures, materials, and parts in different sectors. MIG welding is used in:

• Sheet metal welding. 
• Home improvement, automobile, and automotive industries.
• Fabrication work for pressure vessels and steel structures. 
• Heavy construction, such as building materials and bridges. 
• Welding of pipelines. 
• Repair of automotive. 

Conclusion

MIG welding, or metal inert gas welding, is a versatile and efficient process widely used in various industries like automotive and construction. Developed in 1930 by HM Hobart and PK Devers, MIG welding offers fast and reliable joining of metals using a continuously fed electrode wire and inert gas shield. Its ease of use, versatility, and cost-effectiveness make it a popular choice for both beginners and experienced welders alike. With proper technique and equipment, MIG welding can reliably create strong bonds on a wide range of materials, making it an indispensable tool in manufacturing and fabrication.

Frequently Asked Questions

Can you MIG weld without gas?

MIG welding can be performed without a gas storage tank but requires a customized welder to prevent oxygen reactions using a steel cord with a changing core.

Can we use stainless steel in MIG welding?

MIG welding is a superior method for joining stainless steel due to its continuous wire feed, making it easier than techniques like TIG welding.

Is MIG welding for beginners?

Yes, MIG welding is a beginner-friendly, basic, and affordable approach that uses fairly risk-free and flexible welding compared to various other methods, making it a better option for welding devices.

Is MIG welding as solid as stick welding?

Stick welding produces stronger welds than MIG welding due to its ability to pass through thicker, uncleaner surfaces, making it more reliable and easier to use for deeply bonded joints.