Welding Uphill And Downhill With MIG
MIG welding is often one of the first welding disciplines that most people encounter these days. When they first try their hand at it, people usually are content to run a weld on a piece of metal flat on a table. This is often referred to as the down hand weld or “officially” as a flat weld. This is easy and works well to train basic techniques. But when the basics skill set has been developed, it is time to move on to other positions such as horizontal welding, vertical welding and overhead welding. These positions require more skill and different techniques to perform adequately.
One of the most difficult positions to master is vertical welding. Many people who learn on their own, quickly find out that running a bead “down hill” where the weld is made welding from the top to the bottom of the weld is actually quite easy. This type of weld looks nice, is very fast and the puddle is very easy to control. But upon close inspection this type of weld offers very little penetration on thicker materials. This technique is a valid technique in a limited number of circumtstances. For example, in many trailer plants that manufacture small trailers composed of thin wall tubing or light gauge metal, running down hill will achieve 100% fusion if the welder wire speed is turned up. This is done to prevent overheating and warping of the components. But for anything more than thin gauge material, downhill welding is usually considered taboo. Welding uphill is the method of choice for most welds. It presents a number of problems though for the beginner.
When you are welding uphill, heat builds as the weld is made and as you recall from your basic physics in high school, heat rises. And it really does too. As you weld, the heat travels up the plate (and down some too) and the metal becomes more readily melted and less heat is often required. What happens is a runny weld or one that drips down or sags before it cools. So, the best way to control the weld pool is to actually begin a weave. The weave for uphill is somewhat different than what you would practice for a flat position. It involves actually concentrating and holding the heat on either side of the weld. The motion across the face of the weld is rapid, and almost no metal is deposited. Each side received an equal mount of time though, and a small shelf is built up on either side of the weld. When the weld has build up, and just before it decides to collapse and run down, the torch is redirected across the face of the weld to the other side. What results is a series that looks like 2 U’s side by side, but interlaced with each other in the middle. Of course, some people learn to run stringers uphill as well, and this is fine, but it can lead highly convex welds with slag entrapment if the welds aren't properly cleaned. If you learn uphill at the beginning, it will go a long way toward boosting your confidence as a welder.