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MIG Welding Overview
What Is MIG?
MIG welding is a welding process in which filler wire is automatically fed out of a “MIG Gun” while shielding gas is released from the gun simultaneously. This is quite different than TIG and stick welding because the filler wire flows out at a set rate and keeps on going. With TIG, the welder holds the torch in one hand and also feeds filler rod with the other hand. With stick welding, the electrode with filler rod is constantly getting shorter, which is frustrating for beginners.
MIG welding allows the user to make quick work of projects. You don’t have to switch out electrodes or feed filler rod. Prep your material, dial in the settings, turn your gas on, and start burning.
In this MIG welding overview, MIG may sound easy- but it can be quite challenging to get right at first. There are a number of settings which take time to memorize and practice. One setting unique to MIG is the wire feed speed. Measuring wire speed is a simple reading of inches per minute. MIG wire comes tightly wound on spools and the drive rolls release wire out of the machine towards the tip of the MIG gun.
Using extra large spools of MIG wire is only available on higher end machines. This means the welder can perform many projects or days of welding without worrying about getting new filler wire. However, similar to TIG welding, MIG welding will use a fair amount of gas, and the welder must budget for a gas cylinder and refills.
Many welders are familiar with amperage settings, and TIG and Stick welders have their favorite amperage settings for their machines. MIG machines tend to have a constant voltage (CV) so the power setting is measured in volts instead of amps.
There are many charts available online and included sticker charts on most MIG machines that will tell you what settings are best for different types and gauges of metal. After MIG welding for a while, you’ll have a pretty good idea of what settings you prefer. Having the right settings can drastically improve the look and quality of your MIG welds.
Depositing more material into each weld requires high wire speeds. Higher voltage means the weld will be hotter and can be useful on thicker metal or more industrial jobs.
This MIG welding overview will also cover the main types of MIG wire that are commonly used.
Types Of MIG Wire
“Hardwire” is wire that requires a shielding gas at all times. A 75/25 mix of argon and Co2 is generally used for hardwire, but straight Co2 can be used as well. The reason hardwire requires shielding gas is that there is no flux in the wire. Using hardwire is useful with fabrication jobs, as well as a lot of automotive projects.
If you want to whip out a welding project at home in a timely manner, hardwire will be the most convenient. Penetrating a hardwire weld to its full extent can be tricker than flux core, because it digs less into the metal but- welding with hardwire on thin material can be very productive because it burns through less.
Flux cored wire is MIG wire that contains flux, similar to a stick electrode. You can use flux cored wire without shielding gas, and the result is somewhat similar to a 7018 stick rod. This is a messy process, and generally isn’t quite as smooth as running a 7018 rod. A lot of big box stores will sell MIG machines with no gas inputs, so single shielded flux core is the only way to weld with these. The flux core process can be convenient for someone on a budget that just wants to get a feel for welding.
Dual shield flux core is a process using flux cored wire as well as a shielding gas (usually 75/25 argon/co2). This process is the choice for many ironworkers, fabricators, ship yards and some pipe welders. Dual shield allows for very deep weld penetration and a smoother final product than straight flux cored welding. The flux and shielding gas both protect the arc, which makes it a great process for welding that must be done outdoors or when its windy.
Dual shield flux core tests are very common tests through the American Welding Society. Many welding schools include these tests near the end of their programs as students prepare to enter the workforce. One of my certifications was a vertical uphill flux cored test (3G) and I am happy to have that under my belt. Pleasing employers will become easier with this certification. However, some jobs will require much harder tests before hiring.
A lot of ironworkers and structural welders prefer dual shield over stick welding. This is because it takes less time than stick welding, and more metal can be deposited over the course of a work day.
Dual shield flux cored welding requires more voltage on average than regular hardwire. We don’t recommend dual shield flux core for thin walled material.
Stainless MIG wire is not as popular as the other methods but can be great for fabrication jobs requiring the welder to use stainless steel. This process is very similar to hardwire, but the weld puddle can be harder to manipulate than welding on mild steel. I tend to use a tri-mix shielding gas with stainless MIG. This gas has helium, argon and Co2.
Aluminum MIG welding is also very popular today. It is much faster than aluminum TIG welding. A MIG spool gun is used for this process, because the aluminum wire is so soft, and it can jam very easily. If you used aluminum wire through a regular MIG setup, it would almost always get jammed before it reached the tip of the gun due to the length of the lead. The distance between the small aluminum roll in the spool gun and the workpiece is around 12 inches, so aluminum wire jams a lot less with this setup.
Aluminum MIG welding requires straight argon gas.
Aluminum MIG welding can be frustrating for beginners because it is hard to get a good looking bead. It is recommended to become proficient in hardwire and flux core MIG before you learn aluminum MIG.
Aluminum is a non-ferrous metal, meaning it contains no iron. This makes aluminum very unique because it can never rust when left out in the elements.
MIG welding is a great skill to have and can be useful to hobbyists and professional welders alike. We hoped you enjoyed our MIG welding overview. To learn more about MIG machines and price points, we have an article you can find here.