When people start welding, they almost always learn MIG welding first. This welding method is popular with do-it-yourselfers and fabricators because it offers a great balance of power, flexibility and ease of use. While learning the right techniques may be easy, setting up a MIG welder can be difficult.
With so many choices in wires, gases, settings and machines, it can be hard to find the right setup for your needs. Here’s a breakdown of everything you need to know to get started, from getting the right machine to solving problems with poor welds.
“MIG” stands for Metal Inert Gas. This is a type of welding that uses a wire electrode and gas to bond materials. It’s also referred to as metal arc welding (GMAW), wire welding and wire feed welding.
The welding machine feeds a wire electrode from a spool to the welding gun. An electric arc between the electrode and the piece being bonded creates the heat needed to melt the wire. In most types of MIG welding, an inert shielding gas envelopes the electrode and weld pool, protecting them from oxygen contamination. Reactive gases are also used in some situations, while flux core wiring doesn’t need shielding gas.
In MIG welding, the filler wire is the electrode. This consumable is stored on a spool that’s either on the side of the power supply or on the gun. Pushing the button on the gun sends current through the welder and turns on the wire feed. The feed speed must be adjusted to keep a steady supply of wire running to the weld pool. Some new welders can adjust the wire speed automatically, making it easier to maintain a steady arc.
Solid MIG wire is little more than filler wire. Since it doesn’t have the additives of flux core and stick electrodes, it’s not as good at overcoming rust, oil, dirt and other contaminates. However, it handles these contaminates better than TIG welding. For the best results, the surfaces being welded need to be clean. Wire formulas are available that have added deoxidizers, which helps the weld penetrate rusty metal.
Wire is available in a range of thicknesses. Increasing wire thickness increases the strength of the weld, but it also increases the heat transferred to the metal. 0.030 inch wire is the most common size for general purpose welding, while 0.023 inch wire is used for sheet metal. 0.035 and 0.045 wires are used for welding thick metal parts.
The wire feed setting is in Inches Per Minute (IPM). Increasing the wire diameter decreases the speed it needs to be fed into the weld pool, while increasing the amperage increases the feed speed needed to maintain the arc. 0.023 inch wire needs a feed speed of about 3.5 IPM per amp, while 0.045 inch wire only needs a feed speed of 1 IPM.
Welding wire uses a code to indicate its characteristics. Different code formats are used depending on the metal the wire is designed to weld. All wire codes start with “ER,” which stands for Electrode Wire.
Carbon Steel Wire
For example, ER 70S6 is a solid electrode wire with 70,000 lbs. of tensile strength and level 6 cleaning agents, which is high. This formula is used for welding carbon steel.
Stainless Steel Wire
The most common type of stainless steel wire is ER 309L. It can weld stainless steel, and it can bond stainless and carbon steel pieces together.
ER4043 is a common wire made for 4000 series aluminum. Wire used for aluminum welding is soft and easy to bend, so it requires a special feeder.
Wire stick out is the length of electrode wire extending past the tip of the welding gun. Most welders work best with 3/8 inches of stick out. Get too close, and spatter can weld the electrode wire to the contact tip. Get too far, and the shielding gas won’t cover the weld, resulting in poor bonding.
The direction of movement influences the resulting weld:
In most cases, the gun should be kept at a 5-15 degree angle for the best results. Too much angle can force the electrode away from the puddle, resulting in more spatter, less penetration, and arc instability.
The Advantages of MIG Welding
The Disadvantages of MIG Welding
Where is MIG Welding Used?
The flexibility, small learning curve and small amount of setup needed for MIG welding makes it a great choice for all types of general repair work.