When beginning a career in welding, there are a few techniques and methods that should be consistently used in order to create a sound, high quality weld every time. Most MiG welders have learned their own tips and tricks over time, and experience will always be the best teacher. Knowing how MiG welding works, and what variables can change different aspects of MiG welding is important to get started.
Machine setup is the most important step. The MiG welding process is easy but set-up requires a strong knowledge of the proper settings as well as the materials being worked on. Try to learn on different machines, as this gets you used to adjusting settings and usually there is no room for error!
This welding process uses Direct Current generated from the machine, which is a constant voltage power supply. D/C electricity flows from the negative ( – ) electrode to the positive ( + ) electrode, which then creates the arc.
The electrode for MiG welding is the wire spool, which is fed from the gun. Typically the wire stick-out should be about ¾ of an inch to ¼ of an inch at the least. If the stick-out is too long and the gas–flow is low, the shielding gas will not be able to do its job. Having a high gas-flow with a shorter stick-out will cause disruptions or “turbulence”.
Finding an even balance between these two factors is very important.
Increasing the wire-speed a little will create a globular transfer, taking the speed up a lot will create a short circuit but usually requires a CO2 shielding gas instead of Argon and is almost a different welding process altogether. Slowing down the feed speed with create a spray effect, which is helpful when welding in the overhead position.
Welding comes down to prep and execution. Properly cleaning the work-site ensures that no unwanted contaminates will lessen the quality of your weld. The method of cleaning the base material can vary depending on where you are working. The most common methods are with a wire brush or with a chemical cleaner.
Check the nozzle tip of your MiG gun, this should be free of all slag and should have an even edge to the tip. Having a ragged or partially blocked tip can result in uneven coverage with the shielding gas, which leads to the contamination of the weld site.
Using Proper Techniques
Take the time to evaluate the best technique for the position you are in, location of the weld, and the type of joint needed. This will help you produce a high quality weld.
There are two ways to move your pool across the weld. Using the forehand method, you “push” the molten pool in the direction of the weld. This is the most common method of welding, and typically produces a wide, flat and smooth finished product. However, this method only has a shallow amount of penetration.
The second method to MiG weld is called the backhand, or “dragging” the pool. Because of the wire feeding into the direction that you started, the weld stays in a pool longer. This creates a weld that penetrates deeper, is narrow, and has more build up of material in the middle of the weld.
Regardless of the job, forehand is the most common method for MiG welding.
What the weld looks like at the end is not as important as the four MiG basics. A clean joint, proper machine setup, technique, and being comfortable while completing the job. The commonly used welding patterns actually serve to make it easier to MiG weld by evenly and uniformly spreading the metal, but they do not ensure good weld quality.
The most used welding patterns are; a steady motion, whipping, circles, and weaves. These patterns help welders develop skills so that over time it becomes natural to simply shape the pool and weld as needed. When welding the first pass on a project or working with thin metal, the whip pattern is preferred for optimal penetration and control.
A steady motion is used by most automated welders and requires consistent travel speeds, machine settings, and electrode angles. The hotter that the machine is set at, the better penetration there will be and a higher quality weld will result.
Whipping is a pattern that is can be compared to taking two steps forward and one step back. This preheats the joint before filling it with material, but also keeps the molten puddle in a tight and easily controlled area. This is a great pattern to help new welders learn a consistent travel speed, as well as how heat effects penetration.
Circles work well in most positions and on almost any kind of joint. This pattern is the middle ground between whipping and weaving. It works just as it sounds: make a small circle, move the gun forward, and do it again!
The weaving method can help to cover a wider welding area or is a tighter side-to-side motion. This method can help with weld coverage, but if completed incorrectly the weld penetration will be inadequate. Most companies will not allow welders to use weaving for this reason, and instead have a formula that how much heat (i.e how well the filler is penetrating) is generated with certain travel speeds. With a standardized speed required, this excludes the more free-form weaving method from being used on critical joints.
Comfort Is the Key
Taking your time can be one of the most important things about welding; this starts with preparing your workspace as well as the work-piece. Always set up to be as comfortable and as stable as possible. In a testing environment, the evaluator will typically attempt to get the welder to fail or bust out by rushing them through the test to see how they handle it. Stay calm and stay comfortable.
Welding Position Guidelines
The easiest way to weld is in the Flat Position, with “pushing” the pool being the preferred technique. The MiG gun can be in a 90-degree angle pointing straight down or can have as little as a 35-degree angle with the tip pointing in the direction of travel. If inexperienced, this is the time to turn up the heat to practice good weld penetration. Most of the patterns will work for this position, but a steady motion is preferred.
The Horizontal Position can be a bit trickier; the MiG gun needs to be pointed upwards with an angle of 35 to 45-degrees with a slight tilt of 15 to 35-degrees in the direction of travel. Always make sure to watch for the weld rolling over and any overlap. It is wise to make tight stringer beads for any joint and whipping or circles will work best. Welding in this position requires skill and technique, so do not be discouraged if it takes a few passes to get it down.
Starting at the top of a Vertically Positioned weld is easy. Tilt the MiG gun up about 35 to 45-degrees and keep the electrode moving side-to-side. Vertical positions can be tricky because you need to stay ahead of the puddle; otherwise it is hard to make a weld with good penetration.
Working from the bottom of a Vertical Position can be difficult. Starting with a small groove or “shelf” can help to build up an initial deposit. Angle the MiG gun upwards at 35 to 45-degrees and realize that a vertical up weld is never going to look good. A solution is to make the weld wider, while maintaining penetration. However, the weld is usually going to look very convex. While welding in any vertical position, the weaving pattern is usually preferred.
The least favorite welding position for most newbie welders is the Overhead Position. To start, double-check all PPE being worn. Make sure to tuck in your sleeves to prevent molten metal from running down and burning you. Make sure to keep the MiG gun at a 5 to 35-degree angle moving towards the direction of the weld.
Keeping It Real
Be aware that this technique based industry has been around for a long time, and there will always be somebody who knows more about a welding process or who knows about a different way to get the job done. Being open to constructive criticism is very important and will get you further in a welding career. Additionally, these are guidelines that can help you get on the path to success and the best teacher will always be experience and education.