Welding holds the world together and is an essential part of countless mechanical structures. To learn how to do it, a welder friend suggested I start with MIG welding.
In MIG welding (Metal Inert Gas Welding), a thin wire electrode is fed continuously from a spool. Current passes through the wire, melting it and the base metal to fuse them together. The weld is shielded by an inert gas such as carbon dioxide or argon.
MIG welding has been a popular technique for decades and remains one today. In this article, I’ll tell you everything you need to know about MIG welding, including tips to improve your welding technique and material selection.
What is MIG Welding?
Metal inert gas welding (MIG welding) is also known as gas metal arc welding or wire welding. In arc welding techniques like MIG, an electric current is used to heat metals above their melting point to fuse them together.
Specifically, the current in MIG welding is carried through a wire electrode that automatically spools from a machine. The current and spooling rate can be controlled, and different settings are needed when using different materials. The appropriate settings can usually be found with the welding machine that you’re using.
The current passes from the wire into the base metal, and the circuit is completed by a work lead. In MIG welding, the wire electrode has a positive charge, and the base metal has a negative charge, which is reversed from the usual circuit setups. This is known as reverse polarity.
Unlike other welding techniques, in MIG, the wire also acts as the filler metal, which is the metal that is added during the welding process. You’ll consume the wire while welding by melting it, but the welder machine will automatically feed more.
Tips for MIG Welding
If you’re new to MIG welding, don’t worry – it’s one of the easiest and most efficient ways to learn to weld. There are four things in particular that you should keep in mind when MIG welding:
Specifically, the distance between your welding gun and the base metal should be constant for your entire weld to ensure consistency. If you’re too far, the weld will be weak and porous since the base metal won’t melt as much.
If you’re too close, then you can melt right through the base metal, or you can burn the wire contact all the way to the tip and melt the two together, damaging your nozzle. An ideal distance is between 3/8” and ½” above the base plate.
The angle between your welding nozzle and the base metal also determines how consistent and efficient your welding job is. Ideally, you want to hold the nozzle perpendicular to the plane of the base metal.
If you’re welding a corner, hold the nozzle at a 45-degree angle in the middle. If you work at a bad angle, your weld will be inconsistent, messy, and will splatter.
The travel angle is the angle of your nozzle in the direction of travel. You’ll want to hold the nozzle about 10 degrees from perpendicular, either leading forward (“pushing”) or backward (“dragging”).
There’s not a big difference between pushing and dragging, and in most situations, you can use either. When dragging, you’re likely to get a bit more penetration into the base metal. You should push when working with aluminum because it produces a lot of soot.
For maximum efficiency, you shouldn’t just weld in a straight line. Instead, expert welders rock the tip back and forth in a weaving motion a little bit as they move across the base metal. Alternatively, you could move in circles or curves. You should also try to keep a consistent speed when welding.
If you move across the base metal too quickly, your weld will be narrow; if you move too slow, your weld will be wide, and you could burn through the base metal.
It takes a few tries to get your welding technique just right, so I’d recommend doing a few practice runs. Without hitting the trigger, practice keeping a consistent motion, angle, and distance as you run the nozzle over the base metal.
To keep the nozzle steady, you may find it helpful to use both hands. You can use your other hand to support the wrist of your welding hand. This is a great technique both when practicing and welding, but in some situations like corner welds, you’ll have to manage with just one hand.
Materials Used in MIG Welding
A few different materials are commonly used in MIG welding that will determine the optimal settings and motion for you to use.
First, your base metal and wire/filler metal can vary. MIG welding is great for welding carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze, and other alloys. (Source: Instructables)
There’s a range of filler metals that are used, such as copper, phosphor bronze, red brass, yellow brass, nickel silver, aluminum bronze, silicon bronze, and copper/nickel. (Source: Weld.com)
Shielding gas is dispensed through the nozzle by a gas diffuser. It creates an inert atmosphere where the metals melt and fuse to avoid reacting with oxygen, water vapor, and other chemicals in the air.
Inert gases like carbon dioxide and argon are used, oftentimes in a blended ratio. For hotter welds on heavier base metals, helium can also be used.
How to Weld Brass
Brass is a popular material used in welding, both as a base metal and a filler metal. Here are a few tips to keep in mind when welding brass in particular.
Brass comes in two kinds: red brass and yellow brass. Red brass is an alloy of zinc, copper, and tin, whereas yellow brass is only a combination of zinc and copper. When heating materials containing large amounts of zinc, a lot of bubbling and outgassing can occur. This is a big problem if your base metal is made of brass.
The solution is what welders call “brazing.” Brazing means that your weld melts and adds filler metal without melting the base metal. To braze, you’ll need to use a lower temperature and be sure to pick a filler metal with a melting temperature less than that of the base metal.
Especially when brazing, consistent welding is essential. If your distance is too small or your pace too slow, you’ll melt the base metal, and if your distance is too large or your pace too fast, you won’t get a good weld. When brazing brass, make sure you’re working in a well-ventilated environment, as a lot of hazardous gas can be produced.
Advantages and Disadvantages of MIG Welding
MIG is just one welding technique, and it comes with a handful of advantages and disadvantages. It’s advantageous because it’s great at joining a wide range of base materials and thicknesses, it can be performed in any position, the weld bead is consistent, it doesn’t usually have much splatter, and it’s easy to learn.
Compared to other welding techniques, MIG welding is not as good for thicker base metals. Since it requires inert gas dispensed from a heavy canister, it is less portable than some other types of welding. Some other welding techniques, like tungsten inert gas welding (TIG), are more precise.
MIG welding is the most popular choice for new welders who want to learn. It’s simple – all you really need to do is master the motion of the welding gun. The settings are all determined and controlled by the welder machine, so you don’t need to worry about it.
The materials needed for a MIG welding setup are relatively inexpensive compared to other types of welding. Stop by your local hobby shop to pick them up and start welding today!