Metal Inert Gas (MIG) welding is the most frequently used welding process in the world. It's the type of welder you're most likely to find in your local hardware store or home center. With its affordability and ease of use, it's a great place for beginners to start. MIG welders can work right out of the box using flux-core wire or you can use certain types of compressed gas in conjunction with your welder to expand your ability to weld different materials.
Tools and Safety Equipment
Besides the welder itself, you're going to need some basic safety gear and a few hand tools to get started. First, a welding helmet and a pair of good welding gloves are essential. Do not weld anything without wearing proper safety gear. Next, an angle grinder with a few different discs for cleaning and cutting will help you do the necessary prep work for your welds. A good pair of welding pliers is very useful and should be kept close at hand. It's also a good idea to clamp your work down when possible. There are limitless clamps and magnets available for holding your work in place. Lastly, a safe, non-flammable work surface away from any combustible materials is also essential.
Choose the Right Wire and/or Gas Combo
Before you start to weld the key consideration is what kind of wire or gas combination your project requires. For the beginner, we're going to focus on welding mild carbon steel. You can use flux-core wire if you don't want to keep a tank of gas in your shop, or you can use a mixture of CO2 and Argon called 75/25, along with a solid wire to help produce better welds. Welding supplies and great advice are available at any local welding supply store. A wire/gas combination reduces splatter and helps to shield your welds from contamination. Gasless welds can be achieved, but it is somewhat harder to master.
Eighty Percent of Welding Is Preparation
Before you begin welding, it's critical to prepare the surface of the metal you'll be working on. Clean, bright metal is the best way to ensure that your welds are strong, free of contamination and will generally produce superior results. Do not weld rusted metal or even worse, painted metals. Use a ceramic flap disc in your angle grinder to clean the areas of your welds down to clean bright metal. Make sure to wear gloves and eye protection at the minimum, and if you're cleaning paint, a respirator is a must.
Load Your Wire and Turn On the Gas
Open the side of your welder and load the wire according to the user manual's instructions. Attach your gas regulator and tank, and check for any leaks according to the instructions. If you find a leak, tighten or repair the connection, and test again until there are no leaks. Next, consult the chart on the inside of your welder to determine its correct settings for your project. You'll need to know the type of material, the thickness of the material and the gas/wire combination you plan on running.
Tune Your Welder to the Right Settings
Now that you've got the recommended settings from the chart, it's time to set the welder. Set the wire speed and the voltage to the settings on the chart. These settings are just a recommendation for where to start, so make sure to run a few test welds before actually starting your project. You may need to speed up or slow down the wire feed or increase/decrease voltage depending on the material or other outside factors.
Attach the Lead Clamp
One of the most important things to know when welding is that without a good connection for your welder's lead clamp, you will not produce a good weld. Your lead should be clamped to a clean part of your project or if you're using a steel welding table, you can clamp directly to it. Keep your lead clamped safely and close to where you're working and be aware of its location as you weld.
Support Your Work
While you're welding you'll want to make sure that your work doesn't move around. So, before you start your weld it's a good idea to clamp your work in place. Right-angle magnets like the ones shown are popular, but there are a number of very strong clamps and fixtures available for securing your work.
It's Time to Weld
Once you've made the necessary preparations, it's time to put on your safety gear and make your first weld. Make sure you've got everything on and set accordingly, and with 1/4" of wire sticking out of the end of your gun, stitch the joint together while holding the trigger down. You want to draw a cursive, lowercase "e" all the way down the joint. It takes practice, but with enough time and patience, you'll start to see your welds improving. There are tons of resources online and at your library to help you improve your technique.
A Finished Weld
The objective is to produce a nice straight weld that looks like a small run of circles that overlap each other. You'll notice that your welding activity produces a lot of sparks and heat. If you're welding something complex, you may want to move around and weld other parts of your projects instead of staying in one place. If you weld consistently in one place the heat can cause your project to warp.
Improvement Through Practice
The four examples of welds above show common mistakes and can help you can improve your technique. Weld number one has the wire speed set too slow while weld number two has it set far too fast. Weld number three is a decent weld, but the gun was held too far away from the work surface. Weld number four has the voltage set too low and is causing poor fusion in the weld. Keep practicing and welding and you'll discover a whole new world of DIY projects that are available to you.