MIG welding, short for Metal Inert Gas welding, is usually one of the very first welding methods that most amateur welders encounter these days.
And when enthusiast first tries it, most are more comfortable to run a weld on metals flat on the table, and as a beginner, most projects require welding in flat position. This is usually called the flat weld. It is super easy and works really well when training basic techniques and motions.
However, as a basic skill set develops you are keen to try out other projects that require more advanced positions. There probably will be times when you will need to deal with projects in various sizes and shapes. And in some cases, you may deal with some really large items that would require you to weld vertically welding up or down. This position requires more skills and requires different tricks and techniques unlike just welding in the flat position to create a strong weld.
Vertical MIG up or Down?
Vertical MIG welding is one of the most difficult and tiring welding position to master. Vertical welding position requires you to work against the force of gravity. Thus, you will need to take certain considerations such as a reduction in amperage of your machine at first, because the hotter the puddle, the more easily it will drop to the ground.
A vertical weld can be performed in either downhill vertical or uphill vertically. The direction better for you will depend on your personal preference and skill along with the thickness of materials and filler wire you will be using— a flux core or a solid wire. Also, the vertical down welds tend to be a lot weaker than the vertical up welds, so if you need to weld some constructional details, you better choose vertical up welding.
Vertical Down MIG Welding
Most people who learn to vertical weld on their own use this technique. A vertical down welding starts from the top of the joint, going down to the bottom. This welding position is a lot easier and faster with the puddle being easer to control while providing a clean and nice weld.
It is a process that proves to be better when dealing with thin metals. This is because as you move down, you get a faster travel speed and the arc will penetrate the base metal less. Thus it has lower heat input thanks to the faster welding speed. This also helps to prevent the excess melting or damage to the material, so you should be able to deal with thin metals without a problem.
For instance, in most trailer plants which manufacture small trailers that are made of light gauge metal or thin wall tubing, running a downhill weld can help achieve 100 percent fusion while preventing overheating or even warping of the components.
Furthermore, welders find working with solid core wire is much easier when doing a downhill weld. To get desired results, your MIG welding gun should face the metal at 5 – 15 degrees downwards while moving down in “Z” motions. While keeping the arc in the beginning and in the ending of a Z for a slightly longer, you try to create a chain of dots, connecting them moving fast over the center of the bead. Why you stop at the ending points of the Z and move fast over the middle part of the buddle is to prevent excess metal build-up falling away from the join. You should always try to stay ahead of the puddle.
However, when dealing with thinner metals, a downhill weld can still cause a burn-through if you move too slowly. In addition, for anything more than thin metals, a downhill weld is considered a taboo since it offers little penetration for thicker materials and it almost always fails to fulfill its purpose.
Vertical Up MIG Welding
An uphill welding position is when you start at the bottom of the joint and work your way upward. This welding position is considered mode difficult than a downhill weld. It works really well for dealing with thicker materials; something with at least ¼ inches or more since it provides greater penetration.
In addition, if you use flux core wire, then better results can be achieved when you choose to do an uphill weld in order to prevent contamination of welding puddle by the flux. When doing an uphill weld, your MIG gun should be pointed up and held at an angle between 5 and 15 moving up way up.
Learning how to weld uphill is the method of choice for most vertical welds, it goes a long way to boost your confidence as a welder when you master it. However, it has a number of problems for beginners.
Basic physics taught us that heat rises up and while doing an uphill weld, heat builds as you weld. The heat travels up the plate (yes it travels down too, but not as much) as you weld and the metal becomes more “preheated” it requires less amperage to penetrate the metal the hotter the base metal gets. What happens is a runny, fluid-like weld that drips down before it cools, thus you need to act and move fast.
To help control the shape, size, and cooling of the weld puddle on an uphill weld, you need to make slight weaving motions instead of straight “Z” You should add a weave to it. The weave for uphill is different than what you may have tried and practiced for flat welding positions.
An uphill weave involves holding and concentrating the heat on either side of the weld. The motion across the weld should be quick so that almost no metals are deposited. Each side will receive an equal amount of time and a small “shelf” will build up on either side of the weld.
Once there is a build-up and just before it runs down, you need to redirect the torch across the weld to the other side just like doing a downhill weld, but the timing has to be more precise.
Vertical MIG welding, whether welding uphill or downhill is a daunting task for beginners, trust me I know. Learning it requires patience and if you are not extra careful you will get a rough, uneven bead, possibly with undercuts on both sides of the bead, which as you can assume is a bad thing.
Before you start taking on projects in your neighborhood to make a few extra bucks that require vertical welding, make sure that you know what you are doing. Practice, practice, practice!
A good vertical MIG welding technique should enable you to fight against gravity as it pulls the puddle downward. If properly adopted and mastered, vertical welding position is the most effective base position after flat position to study and take on other positions in the future.