MIG welding is a type of gas metal arc welding. MIG welding like TIG welding use an electric arc, though the techniques are very different. Let’s learn more about MIG welding before we discuss how to safely weld with a MIG welder.
What Is MIG Welding?
A MIG welding machine feeds a continuous solid wire electrode through the welding gun that combines with the weld pool. The term MIG itself is short for metal inert gas. A shielding gas, generally argon gas or an argon mix, is sent or “fed” through the welding gun in order to prevent contamination of the weld pool.
MIG welding is often considered better than TIG or Tungsten Inert Gas welding because you can use these welders on a much wider range of materials. The continuous feed of metal means you can run MIG welders longer than other types of metal arc welders, though there are limits.
The fact that the wire feed acts as both electrode and filler allows you to weld thicker pieces of metal, too. This also makes MIG welding easier to learn.
What You Need to Know Before You Use a MIG Welder
Before you learn how to use mig welder equipment, let’s talk about how to use it safely. A lot of mig welding tutorial videos skip over everything but the most basic safety warnings.
MIG welding like all welding involves heat and the attendant fire risk. Do not try MIG welding near wood, gas cans or any other flammable materials. Wear protective clothing in addition to a face mask. Inspect the wiring before you turn on the welder. Have a carbon dioxide fire extinguisher and a bucket of sand nearby. Do not use water to put out a MIG welding related fire.
The MIG welding equipment comes with a serious shock risk. Turn off the power before you adjust or align drive rolls.
Do not do welding within 20 feet of anyone who may see the flame un-shielded. This is less of an issue if you put up welding curtains around the work area. If in doubt regarding what you may see in your peripheral vision before turning on your own MIG welding gun, flip down the visor.
Verify that the welder glasses are suitable for the application. Know how to use MIG welder glasses properly, so you don’t damage your vision learning how to weld.
It generates smoke and fumes, so only perform MIG welding where there is good ventilation. Better yet, check for gas leaks before you begin work. A respirator may be required, depending on the type of metal you’re welding. Keep degreasers away from welders, because it causes toxic fumes.
How to Use a MIG Welder
We’ve already mentioned that MIG welders can be used on a wide range of materials. We’re going to focus on MIG welder basics. And you’ll start by donning the right safety equipment.
Prep the Tools
They say that preparation is half the battle. You can’t get a good weld if the tools and materials aren’t suitable for the job. Let’s learn how to prep the MIG welding equipment for the average welding job.
Have the Right Wire
You should use the same type of wire as the material you’re welding. For example if you are welding steel, you generally want to use all-purpose steel wire. Higher quality steel wire should be used on dirty or rusty steel. Do not weld galvanized steel with MIG welding.
If you’re going to weld aluminum, use aluminum wire. The diameter of the wire should increase along with the thickness of the material.
Prep the Wire Reel
Prepare the wire reel. The reel should have enough tension so that the wire doesn’t unravel. On the other hand, the tension nut shouldn’t make it hard to pull wire. The first few inches of the wire should be as straight as you can get them, so that they don’t tangle. Feed the wire into the torch. This must be done before you turn the welder on.
Make Sure You Have Gas
Check the gas tank. Open the main valve about half way, and verify that there is gas in it. You don’t to turn on the gas and find out the pressure gauge is wrong; welding without gas will result in nasty splatter.
The pressure in the argon or argon/carbon dioxide tank could be as high as 2500 PSI, but your welding gas regulator should be between 15 and 25 PSI. The ideal pressure will depend on the type of welding gun you’re using.
If you’re going to be welding thick steel, use carbon dioxide gas. If you will be cutting aluminum, use argon gas. If you will be cutting thinner steel, we recommend a mix of argon and carbon dioxide. The standard 75 percent argon, 25 percent carbon dioxide gas mixture is actually called a MIG mix.
Once you have the gas set up, trigger the torch a couple of times to make sure the gas is flowing to the end of the torch.
Prep the Ground Clamp and/or Workpiece
The ground clamp has the cathode that completes the circuit between the welder, the project, and the welding gun. It should be clipped onto the metal that you’re welding or a welding table. You may want to clean the metal you’re going to weld to get a clean, tight weld. This may mean grinding down the edges or wiping away grease. You might get a better end result if you can grind away rust on the surface of the metal, too.
Lay a Bead
You may think you know how to use mig welder, but laying a bead is a chance to practice before you weld two pieces together. It is much easier to grind away a single bad bead than have to grind away and then re-apply a whole metal joint.
Set the MIG welding machine to DCEP, and use a piece of scrap metal of the same material if you have it and try to make a straight line on the surface. Get a feel for the welder with its current configuration. See how well the wire you chose works on this material.
This is the time to adjust the wire speed and power settings. If power is too low, you’ll get splattered weld. If the power is too high, you might melt through the metal workpiece.
Try to keep the electrode extended one quarter to half an inch from the contact tube. This creates a clean, regular weld.
Begin Welding the Workpiece
We’re assuming you have the settings right at this point. You can now start making the weld. In general, you can either make small concentric circles or a zig zag motion while welding the two pieces of metal together. In either case, the welding gun angle shouldn’t be more than ten degrees in most cases. For flat joints, hold the welding gun at a ninety degree angle.
The beads should be one to two inches long. You don’t want the beads to be longer than this, because it could warp the underlying metal.
Weld in whatever direction you’re comfortable with. Push welding or drag welding both have their strengths and weaknesses. For example, drag welding gives you deeper penetration, while push welding produces a wider bead.
Take Ergonomics into Account
Work in whatever sitting, kneeling or standing position works for you. Remember to take ergonomics into account. Don’t kneel or stand for too long, because it can strain your joints. Don’t snap the face guard down with a snap of the neck, unless you want to risk neck pain later. This is actually a common repetitive stress injury for welders.
Make Adjustments as Necessary
If you have switched from a horizontal weld to a vertical weld, lower the amperage to ten to fifteen percent to help fight gravity. Start from the bottom up to increase penetration. You’ll have to increase the travel speed so that the filler doesn’t fall out of the joint, and increase the travel speed.
Are you switching to a flat weld? Keep the amperage the same, but you may want to switch to a smaller diameter wire so that the weld pool doesn’t become too big.
Grind Down the Weld
The need for this step depends on the final application of the metal. You may not care if the weld is raised and visible. If aesthetics or aerodynamics are an issue, you’ll need to put a grinding wheel on an angle grinder. Then you can grind the weld. You could grind off welding splatter, high areas on the weld, or simply grind the whole weld smooth.
Slow down as you approach the surface of the original stock, so you don’t eliminate the weld if the goal is to simply improve its appearance. Note that you need to wear the same safety gear when grinding as you do when welding, since you’re throwing metal particles into the air.
If you find out that the weld did not penetrate properly, you may need to redo the weld so the two pieces are properly joined.
Your welds should get smoother with practice, and grinding will be less necessary. There will be less excess filler as you learn how to adjust the welding technique to fit the situation.