Learn to MIG Weld in a Flash
Sure, you want to learn how to MIG weld. And why not? MIG welding comes in handy practically every day of the week—especially when you do repair work and fabrication.
MIG welding delivers an excellent combination of speed and versatility and is one of the easiest welding processes to learn. In fact, the majority of you reading this article can learn to run a fairly nice bead, in almost no time at all, with MIG welding equipment. All it takes is a little patience, a bit of concentration, and a few hours of dedicated practice.
MIG stands for Metal Inert Gas and is a process of using electricity to melt and join together pieces of metal.
Some also refer to the MIG welding procedure as GMAW (Gas Metal Arc Welding), MAG (Metal Active Gas) welding, or as wire feed welding. Compared to any other method of welding, MIG welding is, hands down, the easiest way to weld.
The MIG welding process was developed for welding aluminum during World War II as a way to increase productivity. Many different materials can be welded with a MIG welder, it is just a function of changing the welding wire (electrode) and the shielding gas. In this article, we focus on welding steel.
In the most basic terms, MIG is sort of like using a crafter's hot glue gun. However, with the MIG process, a continuous, consumable wire electrode (in place of a glue stick), along with shielding gas, are fed through a welding gun. A short circuit is created, producing intense heat that melts the metal and allows the pieces to mix together and then fuse when cooled.
MIG welding is especially useful because it can be used to weld a wide range of metals (including steel, stainless steel, aluminum, and cast iron), as well as braze steel.
In addition to being easy to learn and execute, MIG offers a number of other advantages:
- MIG produces a cleaner weld
- MIG requires less cleanup
- MIG offers multi-position welding capability
- MIG provides the ability to easily join metals of a different thickness
The Ins and Outs of a MIG Machine
A MIG machine is made up of four basic components: the power source, a tank of shielding gas, a welding gun, and a ground cable. Each of these are crucial to the the successful operation of the welder.
The Power Source—Located on the exterior of the power source are the operating controls for the welder. Depending on the unit, these can include an on/off switch, welding amperage and voltage controls, spot and stitch controls, and a transformer adjustment.
Remove the cover and you'll find what can be thought of as two separate machines: 1) the power supply side consisting of the transformer, rectifier, and condensers; 2) the control side consisting of the circuit board, wire feed motor, main relay, and solenoid valve.
Also located in the cabinet is the wire feed system. This consists of a spool of wire and a set of rollers that deliver the wire to the welding gun. The wire feed system is an extremely important part of the welder as a smooth, stable arc depends on a smooth, consistent wire feed.
The Gas Tank—The tank, normally located behind the cabinet, holds the gas (100% Argon for aluminum or a mix of 75% Argon/25% CO2 for steel) that is used to shield the weld as you work. The flowmeter on the tank reduces the pressure in the tank (over 2000 PSI) to a usable pressure, allowing you to precisely monitor the gas flow.
The Welding Gun—The welding gun features a trigger that sends a signal to the machine to start the welding current, to start the wire feed motor, and to turn on the gas. A copper contact tip at the end of the gun takes all the welding current the machine produces and transfers it into the wire. The tip is replaceable and must match the diameter of the wire you're using. The gas nozzle directs flow of the shield gas around the weld, protecting the weld from the atmosphere.
The Ground Clamp—The clamp completes the circuit between the welder, the gun, and the metal being welded.
Start with Safety
When learning anything new, safety should be one of your primary considerations. Overall, MIG welding is typically safe. But MIG welding produces a lot of heat and potentially harmful light, so you should count on taking some safety precautions to protect yourself.
Keep in mind that the light generated by MIG welding is extremely bright, so you'll need a good welding helmet. Today's auto-darkening welding helmets are really preferable as they darken automatically when you strike a welding arc, eliminating the need to raise and lower the mask to see and allowing you to use both hands to weld.
A pair of heavy-duty gloves and protective leather gear is also important. These items offer protection from any bits of molten metal that might splatter from the areas you're working on.
Finally, only work in a well-ventilated area and always keep a fully charged CO2 fire extinguisher handy.
The First Step
The first step in MIG welding is making sure that the surfaces you are going to weld are clean. A few energetic swipes with a wire brush normally do the trick. A dirty surface could cause contamination and create an unstable arc. A very good rule to remember is the more time spent cleaning equates to less time spent welding.
Since the electrode and gas are automatically fed through the MIG welding gun, the basic technique for MIG welding is pretty simple. Maintain a consistent position and orientation between the gun and the area being welded, which results in a smooth, stable welding arc.
For best results, hold the MIG gun at a 45º angle. Position your head so you can see the wire coming out of the welding gun. Wherever you point the wire is where you will weld. Try to maintain a constant arc length (the distance away from the work) and move with a constant speed.
Let's Get Started
We are using the HTP® MIG 200 for this article. The MIG 200 welds up to 3/8" but can also be dialed down to weld thin sheet metal. First, make sure the power switch is set in the "On" position and the ground clamp is properly attached. Make sure you have opened the valve on the tank and that you have adjusted your flowmeter to 15 to 25 cubic feet per hour. Select the correct heat setting for the thickness of material you will be welding, and then, using a piece of scrap metal, adjust the wire feed rate.
There's a relationship between the wire speed and the welding sound. If you set the speed too low, you'll hear a hissing noise and the wire will melt before it hits the work surface. Gradually increase the wire feed rate until you hear a nice, steady buzzing sound. That's where you want to be.
Remember...if you set the wire feed too high, you'll hear it spit and pop, like the wire is trying to melt below the surface of the weld.
The Tack Weld
Start with a tack weld to avoid panel separation when you start welding. Lay the edge of the gun on the work surface with the nozzle resting on the upper piece of metal. Point the wire exactly where you want to start welding and pull the gun trigger. Pulling the trigger starts the wire feed and activates the flow of shielding gas. You can now start welding.
For a tack weld, you want to weld for about 2 seconds—just long enough for a molten puddle to form and join the two pieces of metal together. The tack welds should be two to three inches apart. After you complete the tack welds, hold the welding gun at a 45º angle and get enough wire sticking out so that you can get it right where you want to start welding. Resting the gun slightly on the work piece and maintaining the 45º angle, slowly guide the gun along the materials you're welding in a smooth, constant motion. You always want to keep the welding wire in sight so you can see exactly where you are laying the bead.
Control the bead width by moving the welding gun faster or slower. You can reduce the heat input by turning the heat up and moving the gun much faster, or you can turn the heat down and move the gun a little slower.
Next, Stitch Welding
Stitch welding is just as easy. Simply turn the machine into the stitch welding mode, adjust the time, and start welding. In the stitch welding mode, the machine automatically welds and pauses.
In the stitch welding mode, the machine automatically performs overlapping tack welds. You simply move the welding gun each time the machine pauses. This type of welding helps prevent warpage and burn through because the gas helps cool the weld. Stitch welding, in effect, is just a series of overlapping tack welds that join together to form one continuous bead that looks like a row of fish scales.
Once you're able to lay a bead and stitch weld, you can continue on to the techniques such as plug and spot welding or other more advanced procedures. As we said earlier, it's fairly simple to learn the basics of MIG welding. Then, it's practice, practice, and more practice.
Think of the preceding instructions as a guide to getting you started with MIG welding. Nothing beats getting a MIG gun in your hands and spending a bit of time working on some pieces of metal.
HTP America, Inc.