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MIG Welding Process and Tips

In MIG welding a wire electrode is used to create a flaming arc that generates heat and creates filler material. An inert gas, typically a mixture of argon and carbon dioxide, is released around the weld in order to keep out external contamination. Below are some tips for beginners and experienced welders with a list of additional resources at the end for further reading:

Proper Grounding

According to Welding Tips and Tricks, proper grounding is the most important tip for MIG welding. The entire clamp needs to be made of copper, not just the teeth of the clamp.

Torch Position

Hold your torch at a twenty degree angle from the metal with two hands on the torch. Position your metal so that you have a clear line of vision while working. As you weld, move the torch in a slight zig zag between the two metals. This technique will vary depending on the distance between the two metals. Some welders suggest moving the torch in an arching zig zag that looks like ocean waves curving back sharply.

Torch Techniques

Push Technique: Pushes the torch forward, into the weld. Pull Technique: Drags the torch backward. The drag technique is a common and simple way for beginners to weld. A drag or pull gun technique will give you a bit more penetration and a narrower bead for deeper weld joints. On the other hand, a push gun technique will give you a bit less penetration, and a wider bead.

Tack Welding

When the two metals are too closely aligned, welders begin with a "tack" weld. Each tack is a small spot weld with an inch spacing between each tack. Tacks will hold the metal in place and make a cleaner weld possible. This technique is also known as skip welding. Welding a long seam in one pass will most likely warp the metal.

The Right Metal

MIG welding is typically used for mild steel, stainless steel, and aluminum. A special adapter is required for welding aluminum.

Common Applications

While MIG is a very versatile form of welding, it is commonly used for automotive and small project welding because it's efficient and clean when joining thin metals. Make sure the metal for a particular project isn't too thick for MIG welding. If welding outside, be sure to put up screens or set up behind a wall in order to avoid any kind of breeze, since MIG uses a shielding gas in order to protect the weld.

Cleaning the Weld Joint

Unlike Stick Welding, MIG welding requires a completely clean weld joint in order to weld safely and to create a strong weld. An angle grinder or sander should be used to remove paint, oil, grease, or anything that isn't clean metal.

Maintenance

MIG welder gun nozzles may become jammed with spatter from welding projects that could jam the wire and cause a mess of wire inside the welder. Nozzle dip and anti spatter spray are recommended by welding instructors to keep gun nozzles clean. The liner for the wire feeder should be cleaned out as well.

Shielding Gas

MIG welding is typically performed indoors with ventilation since it requires a shielding gas. This makes MIG more expensive and less versatile than stick welding. Most home projects require a shielding gas that is 75 percent Argon and 25 percent Carbon Dioxide that flows 20 cubic feet per hour, though this may vary depending on the project. Argon is a dangerous gas to inhale, so make sure there is proper ventilation for all projects.

When working with steel, Carbon Dioxide is a good shielding gas, but the Argon/CO2 mixture is better for welding thin steel. Argon alone is used for aluminum, while stainless steels use a mixture of Helium, Argon, and CO2.

Forehand and Backhand Welding

It is much easier to weld when the weld pool is visible. Therefore, many welders use the forehand welding position because it offers the best view of the weld pool. However, it only provides shallow penetration.

On the other hand, backhand welding is difficult to see the pool with the nozzle in the way. However, it is preferred for situations that require deeper penetration into the weld joint. Regardless of the technique used, MIG welding makes it possible to keep both hands on the torch for better control.

Travel Speed

Welders should move their torches at a steady rate that creates a small weld pool. In MIG welding the wire feed speed and amount of amps will determine how fast to travel. Thin metal requires a slower travel speed than thick metal. Thick metal requires a slower travel speed in order to achieve sufficient penetration into the joint. Keep the torch at the leading edge of the weld pool without letting the pool become too large. Moving too fast or too slow will result in a weak weld joint.

Wire Thickness

Many MIG welding projects can be completed with anything from 0.030 to 0.035-inch wire. Hobby welders will find that 0.030 inches will be sufficient for their needs, while the thicker 0.035 inch wire is typically used for structural welding. The advantage of a thinner wire is that it's easier to control the weld pool with less wire melting.

Wire Stick Out

Opinions vary about the best wire stick out position for welding, though the general rule is to keep the wire stick out as little as possible. The wire stick out is how much wire is protruding from the MIG welding tip (AKA the contact tip) to the arc. With too much wire sticking out, the weld will pile up. The typical stick out will be anywhere from 1/2 inch to 1/8 inch depending on the thickness of the metal.

A wide joint will need about 1/2 inch of stick out. For a particularly thin gage of metal, use more stick out (3/4 inch) and use the push or forehand welding technique in order to avoid melting too much wire in the joint.

Welding Positions

The ideal welding position is horizontal on a level surface. However, when forced to weld in a different position, keep the weld pool small in order to maximize control. Welding uphill will produce a much stronger weld and is recommended for surfaces that are thicker than 1/4" in order to achieve maximum penetration into the weld joint.

Auto-Darkening Helmets

In MIG welding precision is everything. One slight shift can send a weld off-center. An auto-darkening helmet makes it possible to keep both hands on the torch, start welding, and never miss a beat. The torch will stay in the right position, while the helmet will auto-darken when the sparks begin to fly. Welders swear by these helmets that are not only safe, but efficient because they save on grinding time when a weld goes wrong.

Wire Set Up

When loading a wire feeder for a MIG welder, make sure the spool of wire doesn't unroll without maintaining enough tension. However, beware of tightening the wire too much. In addition, the wire should be stored in a location that is free from contaminants and moisture that can ruin a weld.