Metal Inert Gas (MIG) welding is an arc welding technique that works with a continuous solid wire electrode heated and introduced into the weld pool through the welding gun. A shielding gas is fed together with the electrode, which helps to protect the weld pool from airborne contaminants.
In its working, MIG welding makes use of a constant voltage power supply to create an electric arc that fuses the base metal. Also, an inert shielding gas is fed through the gun from atmospheric contamination. Finally, a filler wire is continuously fed through the welding torch. Well, in this reading, we’ll explore what MIG welding is, its applications, parts, equipment, diagram, advantages, disadvantages, and how it works.
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What is Metal Inert Gas (MIG) Welding?
MIG welding is also known as gas metal arc welding (GMAW), which uses a continuously fed solid wire electrode. It melts the base materials together, which solidifies and produces bonds using the welding gun. The welding gun also feeds an inert shielding gas alongside a wire electrode. This helps to protect the process from airborne contaminants.
MIG welding is an arc welding process, which is shielded by external gas welding (argon, helium, co2, argon + oxygen, or other gas mixture.) It uses consumable electrode wire, which has a chemical composition similar to the parent material. This process is semi-automatic due to the automatic feeding of the filling wire electrode. The operator only controls the torch positioning and the welding speed.
Applications of MIG Welding
MIG welding is a popular welding method used in various industries, including home hobby and DIY projects. It is a fast and versatile method suitable for various metals and thicknesses. MIG welding is ideal for first-time welders and welders with less experience, making it a perfect choice for car repairs.
It is also suitable for farm repairs and outdoor use, as the gasless MIG option (FCAW) is practical for outdoor use. MIG welding is also commonly used for general fabrication, such as frames and trailers. In construction, its speed, ability to weld thick metal, and minimal clean-up make it a time and money saver.
The gases are normally used on steel; co2 argon + 2 to 5% oxygen and argon +5 to 2% co2 and nonferrous metals like aluminum, copper or nickel alloys, argon, argon/helium.
MIG Welding Parts and Equipment
A MIG welding machine consist of the power source, and welding gun, then inert gas supply and wire electrode.
Power Source
MIG welding equipment is a modern method that auto-corrects current when arc length and wire feed speed change, creating a stable weld puddle. There are two options for MIG welding: DC positive polarity (DCEP) and DC negative polarity (DCEN). DCEP offers a stable arc, better bead quality, weld penetration, and less spatter, suitable for both thick and thin materials.
DCEN offers faster deposition rates but lacks penetration and heat in the weld pool. AC power is rarely used in MIG welding, but is necessary for TIG welding of aluminum, which requires constant switching between positive and negative currents to remove oxide film on the metal’s surface.
Welding Gun
MIG torches are versatile tools for melting metals, with gas-cooled torches being limited to minor projects due to overheating issues. Water-cooled torches offer more power and smoother control, but cost 20-30% more and require a water-cooled system. There are four nozzle types used in a welding torch: recessed, flush, protruding, and adjustable, depending on the wire electrode used.
Inert Gas Supply
MIG welding involves using a welding torch to supply gas to the welding zone, ensuring the weld pool remains free from contamination. Common gases used include argon and helium, which are expensive and mixed with other gases. Semi-inert gases, including carbon dioxide, are also used for deeper penetration but require more cleanup. Non-inert gases, like oxygen, are used in small amounts to increase metal penetration, but they can cause rust and oxidation, affecting the weld’s quality.
Wire Electrode
MIG users utilize various wire electrodes for different projects and metals. Hard wire is the most common wire used due to its affordability and ease of control. Flux-cored wire, a type of flux-cored arc welding (FCAW), requires no shielding gas and is portable, making it suitable for outdoor and windy conditions.
However, these wires create slag during welding, making it essential to invest in a good metal brush for cleaning. Overall, the choice of wire electrodes is crucial for the successful welding process.
Diagram of MIG Welding
How Does MIG Welding Works?
This welding process is achieved when a cable from either AC or DC power supply is connected to a consumable electrode (welding gun) and the earth cable is placed on the workpiece. At this point, the welding gun is carrying current. Whenever it is placed close to the workpiece, an arc is produced.
The arc melts the base metal and an inert gas supply is provided around the electrode during the process. This gas shield is around the arc and the weld pool, helping to protect the weld from the external atmosphere. At this point, it solidifies and the joint is obtained.
How to Setup a MIG Welding?
Before striking an arc with a MIG welder, ensure that your metal is clean and free of contaminants. Use a metal brush or grinder to clean the metal to bare, and ensure that your work clamp connects to clean metal. Bevel the joint to produce strong welds on thicker metal, especially for butt joints.
Set up your machine by checking your cables, selecting the electrode polarity, setting gas flow, checking tension, and inspecting consumables. Make sure all cable connections are tight and free of fraying or damage. Set the shielding gas to 20 to 25 cubic feet per hour, and if you notice leaks, discard the hose and install a new one. Adjust the tension according to your owner’s manual.
Inspect your consumables, such as contact tubes, contact tips, and liners, to ensure good wire feeding performance. Remember to be sure to set up your machine correctly before striking an arc.
Good MIG Welding Welds
To create a good MIG weld, start by getting comfortable with the welding gun and practicing moving the gun back and forth over the work surface. Clean your metalwork surface to prevent porosity and contaminants from trapping in the weld. Use a deoxidizer in your wire to prevent holes.
Ensure a strong ground clamp, such as copper grounds, to create a smooth flow of electricity. Lesser quality ground clamps, such as plated steel with copper jaws, are not as good as full copper grounds. Place the ground close to the arc and firmly attached to the clean, bare metal to create a smooth flow of electricity.
Set your MIG welder correctly by adjusting the voltage and wire speed to the thickness of the metal you are welding. Test the wire by making practice welds on scrap metal and adjusting the wire speed or voltage rate as needed.
Read your weld bead to determine the level of heat input. A convex-shaped, ropy bead indicates that the settings are too cold, and you can adjust the welding angle by 5 or 10 degrees to improve penetration. A concave-shaped bead indicates a problem with heat input.
Related: What is Gas Welding? Its Diagram, Types & How it Works
Advantages and Disadvantages of MIG Welding
MIG welding is a highly efficient and versatile welding technique that offers numerous advantages, including speed, quality, cleanliness, versatility, ease of use, and versatility. It can be used on various materials such as steel, stainless steel, cast iron, magnesium, and aluminum, and can be done semi- or fully autonomously. The MIG torch’s simplicity and automated functions make it one of the first welding procedures for beginners, freeing them from dealing with technicalities of welding equipment.
However, there are some drawbacks to MIG welding. Cost is an issue, as it requires expensive setup and maintenance, including shielding gas, replacement parts, nozzles, electrodes, and related tools. Personal protective equipment is also essential, especially in extensive production facilities.
Limited positions are another disadvantage, as MIG welding is not suitable for vertical or overhead welding due to its high heat input. MIG welders are also unsuitable for outdoor welding due to wind damage and the need for shielding gas. They can also be difficult to transport and maintain, making it suitable only for garage work.
Fast cooling rates are possible with MIG welding, but it is not suitable for thick metals. Shielding gas can take time to replace and can interfere with welding. Additionally, metal preparation time is crucial for a good weld and safety. Overall, while MIG welding offers numerous benefits, it is important to consider its drawbacks and potential limitations when choosing a welding tool.