Welding Speeds: Distortion, Stress, and Recommendations

February 01, 2024 · Leave a comment · Red-D-Arc
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There are only a few factors you can control when welding, and one of the easiest and most impactful is the speed at which you travel across a joint to fuse metals together.

Known simply as “welding speed,” the travel speed heavily impacts the resulting quality of the weld. It also impacts the risk of distortion in base materials and the stress resistance of the finished product.

The question is, how? What do you need to know?

Welding Speeds and the Quality of a Weld

The quality of a weld can be defined both as the resulting strength of the weld and its appearance, depending on the needs of the finished product. Both are impacted by the speed you travel when welding.

In general, the higher the speed, the worse the weld quality is likely to be. Higher speeds mean less penetration of heat in the joint, which means your weld is more surface-level and less deep. In extreme cases, there’s no real penetration at all, and your weld is essentially like taping the materials together with nothing internal to the joint hem.

Meanwhile, the slower the speed, the more you risk specific problems. Slow travel speeds increase the heat put into a given spot, which means deeper penetration. This can be good for thicker materials, but the thinner the material is, the more you risk completely melting away the material and leaving a gap, known as burn-through.

Greater heat concentrations also broaden the heat-affected zone around the weld, which can distort the base materials and cause them to warp and twist. You can also end up with welds that have voids and gaps – making them porous and weak – and, in some alloys, can even cause chemical changes to the base metal, weakening it.

When it comes to managing the potential distortion of your base materials, there are a lot of different ways to address the problem. Sporadic and semi-random welding, like tack welding, is a common solution for thin materials, for example. In general, to minimize distortion, you need to minimize concentrated heat, which means faster travel speeds.

Thicker materials don’t distort as readily as thinner materials, but this also depends on the specific materials being used. The more diffuse the heat is, and the lower the heat is, the less likely there is to be distortion. Distortion can also be minimized through the use of supporting structures, including thermally conductive heatsink backer bars.

Just about everything else about a weld – from the voltage you use to the shielding gas to the type of current to the filler – is determined before you even begin welding. Thus, travel speed remains the primary skill that a welder needs to learn.

Different Processes React Differently

It should come as no surprise that different welding processes can cause different reactions according to travel speed. Some are more forgiving than others. This is actually why certain welding processes are considered more “beginner-friendly” than others; they leave more room for error in travel speeds, so mistakes aren’t as detrimental or as devastating to the finished product.

Stick Welding is relatively less sensitive to changes in welding speed, particularly compared to other welding processes. Slower speeds are less likely to cause distortion or damage to a weld. Faster speeds can still result in incomplete fusion, however, so it’s usually better to err on the side of slower travel speeds when you’re using a stick as your process.

Other factors that are important for stick welding are the angle of the electrode and the overall technique and motion being used. These can influence distortion more than welding speed, so getting them right is also critical. Stick welding is less common now than it used to be primarily because many of these factors are controlled for in other situations using other processes.

MIG Welding is the most common process, yet it’s surprisingly sensitive to welding speed. Higher speeds, of course, lead to insufficient penetration and weaker welds, though you aren’t at risk of causing distortion when you move too fast on all but the thinnest materials. Conversely, slower travel speeds are more likely to cause distortion and risk burning through the material.

There are a variety of ways you can help with this. For example, using Pulsed MIG. Pulsed MIG is a computerized setting on modern MIG welders that rapidly oscillates the current used in your torch between a higher peak voltage and a lower base voltage. This gives you more flexibility; you can travel slower while knowing that the overall heat put into the workpiece is lower, as is the risk of burn-through and distortion.

TIG Welding is often considered an advanced process, and it’s generally very precise, which means that the travel speed impacts the quality of your weld significantly. The slower your speeds, the more likely you are to cause distortion, and while distortion is lower than you might get with something like MIG or Stick, it can still occur.

Conversely, the faster you move, the more likely you are to end up with incomplete fusion. This is pretty much always going to be the case with any welding process; moving too fast just doesn’t give your current enough time to penetrate deeper into the material to melt and fuse your workpieces.

FCAW, or Flux-Cored Arc Welding, is also a relatively forgiving process. The dual-shielding nature of the process allows you to control heat more effectively, but you will also need to adjust your travel speed not just for the workpieces and current you use but for the type of filler you use as well. This means it can be complex to know how to use, even if it’s often somewhat more forgiving in terms of distortion.

How to Improve Welding Skills with Travel Speed

As we mentioned, learning how to identify the right travel speed for a given project is one of the most important skills a welder can have.

For a weld to be strong, it needs to achieve full penetration without burning through and leaving holes or gaps in the materials. Other concerns, like inclusions, are more controlled with the right use of shielding gas and the right choice of filler material.

So, how can you level up your skills as a welder? Learn how to determine the right travel speed. There are a bunch of different ways you can do this.

First, you can learn the intricacies of each welding process. Stick, MIG, TIG, and FCAW all have their own pros and cons, their own set of factors that can influence the appropriate motion for a weld, and even their own ideal projects. This is why many welders pick a starting process like MIG to learn, and once they become more comfortable with it, they can branch out into other processes and learn how they differ. It’s never a bad idea to have a baseline level of experience from which to draw.

The second thing to do is know what your project is.

  • What metal is the base material? Some metals are more thermally resistant than others, so they require a slower travel speed in order to achieve full penetration.
  • How thick are the workpieces? The thicker the metal, the slower you need to travel across it to achieve full penetration for a strong weld.
  • What are the current and other settings on your welding machine? Higher current means higher heat, which means faster travel speed, in general. Other settings, like pulsing current, can change the equation.
  • Is there any preparation for a weld? Often, thicker materials may have bevels to achieve a flush weld rather than a beaded weld. This, among other things, allows you to treat a joint as though it’s thinner materials than the base material implies; beveling removes material along the path of the weld, effectively making it thinner.

You may also need to be concerned with things like position and conditions. Underwater welding has different specifications than surface welding; pipe welding has different considerations; welding overheats or vertically can impact heat differently, and more.

When in doubt, particularly if you’re working on professional projects (rather than break-fix style repairs that need to be done on the fly), you will likely have engineers working on a welding procedure specifications document for the project. These documents typically include all of the appropriate settings, materials, details, and more and will have recommended speeds for your welding. There are also general reference tables for common materials and joint types that can give you an idea of where to start.

Another beneficial skill to learn is how to recognize when your travel speed is wrong.

Obviously, if you’re moving too slow and you burn through the material, you’re going to leave a hole, and it’s going to be obvious. However, traveling slightly too slow or slightly too fast might not be as visible. How can you identify when your travel speed is incorrect, barring the obvious signs like distortion and burn-through?

  • The bead is very narrow. A narrow bead, particularly one that wavers across the centerline of the joint, likely means you’re moving too fast.
  • The bead is thick and dense. This is usually a sign that you’re moving too slowly, though it can also indicate a filler feed speed that is too high for the travel speed. You’re depositing too much material in any given spot.
  • Your beat is concave. Sometimes, you may melt too much, and the weld bead sinks, but it doesn’t melt all the way through. This leaves a seemingly indented bead that indicates too slow a speed.

You can see a variety of examples of how speed and other faults are visible in a bead from resources like this one. Once you learn to recognize what a fault looks like, you can learn to adjust before it becomes a problem.

Finally, practice makes perfect. When in doubt, try, and don’t be afraid to fail. When you’re using scrap metals, off-cuts, and other materials to test your welding, you can do whatever you want with them and not feel like you’re wasting time or materials. Practicing will give you a feel for how different settings will affect your weld and how fast you need to move when you adjust different settings.

If you aren’t sure or aren’t confident enough to practice on your own, there are many welding classes and training programs that can help upskill you from a novice to an experienced welding adept. Under the skilled hands of an experienced technician or instructor, you can learn quite a lot. You may also be able to work with mentors directly on specific projects and learn how they know what speed to travel at and how to recognize when travel speed is off.

Eliminating the Human Element

One benefit of modern welding is that you aren’t always even required to learn how to adjust for travel speed in welding. Specifically, because there are computer-controlled machines that can weld entire projects for you, all you need to know is how to input the specifications of a project into a computer.

These are, of course, much more common in larger-scale fabrication. They can be found in some bespoke project workshops but more often are used for repeated, high-volume projects. Learning how to program welding machines is an important skill that will pave the way to a career in fabrication and manufacturing far more than skill in individual welding will.

That’s not to say that individual handheld welding isn’t worthwhile. There are always going to be instances where welding needs to be done, particularly for sectors where you can’t bring in a large machine or bring a project to the machine. Underwater welding, aerospace welding, and automotive repairs; these kinds of industries still need that hands-on touch. There will always be room for talented individual welders.

Whether you need a new machine to practice your skills, want to upgrade to one with more forgiving settings like pulsed current, or want to invest in an entire automated welding system, we’ve got you covered. Our welding equipment rentals cover all the bases; all you need to do is pick the one you want and rent it to give it a try. Then, if you like it, buy one from our used equipment store and keep on rolling.

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