MIG Welding Basics

So you finally pulled the trigger and bought one of our Eastwood MIG welders. Now what? As simple as MIG welding is, most hobbyists can't just grab the gun and start laying down beautiful welds that hold together. Getting the most out of your equipment takes time. Practice and understanding the differences in metals, gasses and techniques are the keys to producing top-quality welds. To help you along in your quest of metal fusion, we have put together this guide of tips, tricks and techniques to get it done. MIG (Metal Inert Gas) welding is a style of GMAW (Gas Metal Arc Welding) electrical welding. Metal filler wire is fed through a handheld gun, providing the arc to melt the metals, welding them together. Most MIG systems use a separate inert gas, most commonly a mix of CO2 and Argon, to shield the arc from contaminants. Non-gas systems use flux-core wire, which has flux in the center of the wire. As the wire melts, so does the flux, releasing the inert gas which shields the weld. MIG welding was originally developed in 1948. Unlike today, its primary use then was welding non-ferrous metals such as aluminum. The advent of carbon dioxide shielding gas made MIG welding a viable (and inexpensive) method of welding ferrous metals too, and today it is the standard by which most welds are made. The shielding gas is of utmost importance for MIG welding. While flux-core MIG welds certainly work, you can almost always get better results with solid-core wire and shielding gas. Flux core welding produces more slag and coats the weld with residue, much like stick welding. Eliminating that coating and extra slag means less time to clean up the welds and in the end, results in cleaner, better welds. There are several options for shielding gas, each with its own specific use. Flux-core welding certainly has its uses; dirty metal, windy conditions, and thicker metals (such as car frames) are well-suited for flux-core welding because the wire itself carries the shielding, and flux-core runs hotter than solid core wire.

Carbon Dioxide

Pure CO2 is sometimes used for MIG shield gas. It offers deep penetration and minimizes spatter, but is also helps form oxides, which are bad for fresh welds. The weld penetration is so deep that pure CO2 makes welding thin sheet metal difficult.

Argon & Helium

Welding aluminum and other non-ferrous metals requires pure argon or helium. You can use CO2 mixes with aluminum, but the results are very dirty with lots of contamination. The drawback of these pure gasses comes in welding steel. Argon with steel results in shallow penetration, and with helium, encourages spatter and can cause an erratic arc. Argon and helium are sometimes mixed to create a super-inert shielding gas that combines the best of both worlds.

CO2/Argon Mixes

To get the most from your welding experience, Argon and CO2 should be mixed when welding ferrous metals such as steel and stainless steel. The most typical mixes are 75/25 CO2 to Argon and 90/10. The higher the carbon content, the more intense the arc becomes, increasing the energy in the weld. Welding thin sheet metal is easier with a 75/25 mix. Adding hydrogen to the mix is good for welding nickel and stainless steel. The most typical hobbyist use for MIG welding is steel, which means that the standard 75/25 CO2/Argon mix is sufficient. If you want to MIG-weld aluminum, then you need to invest in a second bottle of pure Argon. Flow rates for MIG welding vary, but most manufacturers suggest starting off with 15-30 cubic feet per hour depending on the materials, your skill level, and the conditions you are welding in. Welding outside or in a garage with the door open creates the opportunity for wind to blow or draft away your shielding gas. If there is not enough shielding gas, your welds will be porous, meaning voids in the middle of the weld. It may look solid on the outside, but inside, it looks like a sponge. Porous welds are very weak, not to mention ugly as sin. If the weld is popping, with lots of spatter, check your flow rate. Too much shielding gas will actually create turbulence, causing outside air to be pulled into the mix, and you get about the same results as you would with too little gas. Aside from your gauges on the tank, your ears are an excellent tool for setting the flow rate. With everything set correctly, you should hear a crackly hiss, no big pops or sputtering.

Wire Size

The wire is the filler material. In general, the thicker the material you are welding, the more filler material you will need. There are 4 common wire sizes for solid-core and 2 sizes for flux-core. To weld thin metal, such as sheet steel, the smaller wire is preferred (0.024"; Eastwood sells 0.023" Solid MIG Wire), as it burns a little cooler and leaves less filler material. 0.030" wire is a good middle-ground wire, and will safely work for 22-gauge up to 1/8" steel in a single pass. The next larger size (0.035") in solid core wire is good for as thin as 18-gauge and up to 1/2". Flux-core wire is available in 0.035" and 0.045" (Eastwood offers 0.030" Flux Core Wire), which is why flux-core wire is more difficult to use on sheet metal. You need to match the wire to the base material; otherwise you will have serious problems.

MIG Pliers

MIG Pliers should be the second tool in your cart after selecting a welder. This multi-tasking tool can be used to clean spatter from the gun tip, pull and cut wire, and aid in the installation of tips and nozzles. Can you use tools you have on hand for these tasks? Sure, but with MIG pliers, you have one tool that is kept on your welding cart and always there when you need it.