On thinner-wall pipe, downhill welding enables operators to run “hot and fast,” increasing productivity compared to welding uphill, which is required on thicker wall pipe to increase heat input to ensure complete penetration.
While both methods have their advantages and disadvantages, uphill is generally preferred for its higher quality and better penetration, especially in thicker materials. However, downhill is faster and can be used for thinner materials.
Downhill welding, on the other hand, is faster, and is largely a matter of keeping the molten puddle from outrunning the arc. It moves quickly, less material is deposited, and as a result, downhill welding is far easier.
As you may know, we use either downhill or uphill welding in the vertical position. Downhill welding is carried out with a downward progression, conversely, uphill moves in an upward progression.
The overhead position is the most challenging welding position, as gravity can cause the weld metal and slag to fall out of the joint.
An edge joint is the weakest type of weld join, so isn't suitable for load-bearing jobs.
Flat Welding Position
Also known as the downhand position, the flat position is the easiest of all the welding positions. A flat position is the common type of weld. It is the first weld that beginners learn. In this position, you are not welding against gravity.
Downhill welding doesn't achieve enough penetration, or leave enough filler metal deposit for most structural applications. Pipe fitters often use it for the first pass on pipe applications, but they then run additional passes over it, usually vertically uphill.
On thinner-wall pipe, downhill welding enables operators to run “hot and fast,” increasing productivity compared to welding uphill, which is required on thicker wall pipe to increase heat input to ensure complete penetration.
The challenging overhead position is performed with the torch at a 45-degree angle, and the 4G and 4F welding positions are appropriate for groove and fillet welds. Remember, the metal can sag from the plate, causing a crown, so keep the molten metal puddle small to avoid this.
What Joint Is Strongest To Weld? Most people consider the strongest joint to weld to be arc welding a corner or tee joint with a groove.
The upside down V is one of the most effective techniques for vertical mig welding of lap and tee fillet welds. Sure there are other ways of making a good looking vertical uphill weld, but for ensuring penetration as well as making a good looking uniform weld, the upside down V is a very good way to go.
Gas Tungsten Arc Welding (TIG) is probably the highest quality and most expensive of the arc welding processes. It is generally performed manually; however, there are some automatic applications. A good welder can deposit ½ pound of weld metal per hour at about 1-to-3-inches-per-minute travel.
Drawbacks to Downhill Welding
While speed is a benefit to downhill pipe welding, it's also a major drawback. Because you need to work quickly to stay ahead of gravity and weld pool, it ultimately leads to less fusion and penetration.
This can be due to the working conditions as well as factors such as the travel angle of the weld, the pipe position and the diameter of the pipe. The difficulty increases as the position changes from 1G to 6G (see 'Pipe Welding Positions' above).
While it is true that welded pipe, in theory, is weaker when it is welded. Many advances in the welding process and quality checks have closed the gap. However, technically speaking, seamless pipe is still stronger on paper and in extreme applications.
Generally, flat is an easier position to weld in since you're not fighting gravity. The weld puddle stays fluid and wets into the joint evenly. As a result, operators can typically run hotter with higher deposition rates. You can use any welding process to weld in the flat position.
Welding in the rain can be dangerous because the water can conduct electricity and cause shock or burns. If you must weld in the rain, be sure to wear protective clothing and take precautions to avoid electrical hazards.
Any imperfections in the metals being joined together can result in joint failure. For instance, parts that were exposed to high heat might have distortions that make it harder for welders to achieve proper alignment.
Welding joins metals by melting and fusing them together, typically with the addition of a welding filler metal. The joints produced are strong – usually as strong as the metals joined, or even stronger. To fuse the metals, you apply a concentrated heat directly to the joint area.
6010/6011 is traditionally used for downhill. 6013 or 6014 can also be used. All these have a thin highly fluid slag which makes slag inclusions much less likely. 6013 is designed to be a low-penetrating rod which is why you should probably use it on unusually thin stuff like under 12 ga.
It can be a stressful job, too, given the level of danger to personal safety and the need to do high-quality work for projects that can range from working on a skyscraper to working on airplanes. It can be a rewarding job, though.
Welding is a labor-intensive career; you operate large machinery and work with delicate materials using high heat.
Welding is physically demanding and takes some practical coordination to master. It's not as physical as a builder's job, but there's usually a fair amount of lifting and climbing over things, which some people don't like.