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Inert gas welding: How to recognize and avoid welding defects

Even if gas-shielded welding is not a problem in itself, one thing or the other can go wrong here too. We have compiled the most important mistakes and tell you how to avoid them.

Problem-free inert gas welding begins with preparation. And that includes choosing the right welding wire and, above all, the right shielding gas. Both have to go together. In gas-shielded welding, a distinction is made between two basic processes. MIG welding works with an inert gas that does not react with the weld metal during welding. It is passive. With MAG welding, on the other hand, the gas reacts with the weld pool and thus ensures, for example, a deeper penetration.

Active gases require high alloys

For structural steel, for example, the noble gas argon becomes about 25 percent CO2 mixed in. As an alternative, pure CO2 use. The disadvantages: spatter and rough seams, thin sheets are difficult to weld. The following applies: the more active the gas, the higher the alloy in the welding wire must be. The height of this alloy can be recognized by the name of the wire. For example, wires with the designation G2S11, G3S11 or G4S11 are popular with practitioners. The number after the G indicates the alloy. A wire of the specification G3S11 with a thickness of 0.8 mm is considered universal by experienced welders and is up to practically any task in terms of structural steel.

The task becomes more complex with stainless steel. Here the welding wire has to match the material to be welded exactly, and the gas mixture has to be adjusted accordingly. Pure argon, for example, does not work, the CO2 The proportion must not be too high so that the alloy components do not burn.

Clamp the wire optimally

When setting the welding machine, care should be taken not to clamp the welding wire too tightly. If the wire sticks to the current contact tube, the feed must slip, otherwise the machine will unwind the wire inside and possibly create a short circuit. Correctly set, the wire feed can be stopped with the thumb, index and middle finger. The welding machine also has a brake that can be adjusted. If the feed is at the highest level, the roller must stop immediately when the torch switch is released.

Welding failure - failure of the joint

Even with the welding itself, one or the other mishap can still happen. Most of the time, the problem can be solved quickly if you take a close look at the weld seam.

For example, it is easy to spot a lack of fusion. There is no correct connection between the weld metal and the base material. As a result, the connection wobbles or even breaks apart. The reason could be an incorrectly set welding power. But there may also be a technical problem. Welding too quickly, off-centering the arc or a downward welding direction can trigger these problems.

Cracks and warpage

Workpieces have an internal tension that is greatly changed by the heating during welding. When expanding or contracting, cracks can occur which, in the worst case, make the workpiece unusable. The behavior can be influenced within limits via the welding performance, but environmental parameters also play a role.

The warpage is also due to the development of heat. It can become so large that the final dimension of the workpiece changes significantly. Warpage can be countered by not pulling the weld seam all at once, but rather in several pieces, for example, and giving the workpiece time to cool down. A similar effect is obtained by alternating between the beginning and the end of the seam.

Too little penetration

Quite similar reasons can lead to a different problem picture. If the weld seam does not fill the gap between the workpieces, this may also be due to the welding speed being too high or the welding power being too low. It is also possible that the weld seam was not properly prepared. In this case, the root opening should be enlarged

Seam superelevation

Rather the opposite of too little penetration is a seam superelevation. It then looks like too much material has been applied to the weld. The reason may be that the welding was too slow here or that the electrode diameter is simply too large. Welding faster or using a thinner wire can be the solution here.


If the weld seam is sometimes thick and sometimes thin, it may have something to do with the welding technology. The angle of attack may be incorrect or the arc may be too long. Another possible reason: the set welding line is too high. One cause that may not be immediately apparent: the magnetic arc-blowing effect. In this case, it helps to move the ground clamp.

Porous seam

Does the weld look like small particles are trapped in it? then gases have collected in the seam which prevent the melt from running together. Bad preparation of the material is often to blame for this. Such a weld seam pattern can, for example, trigger moisture, contamination or coatings that have not been removed. Another possible reason: incorrect welding parameters or too much or too little shielding gas.

Weld spatter

If there are small spatters of the weld pool next to the seam, the cause is usually a problem with the settings. The wrong polarity may have been selected or one of the welding parameters may have been incorrectly set. It is also possible that the filler material or the shielding gas does not fit. An incorrect composition or poor quality can be the reason.


If foreign bodies can be seen in the weld seam, caution is required. You can permanently weaken the weld. Unfortunately, it is difficult to remove from the solidified seam. These foreign bodies can be slag, oxide deposits or shavings from the workshop. So working cleanly is important. If the inclusions occur more frequently, this may also be due to insufficient welding lead or the fact that too little shielding gas was used. Slag that is running ahead can also be the cause. In the latter case, the arc should be held more towards the weld pool. Then it also works with the seam.

Conclusion Recognize and avoid welding defects

Even if inert gas welding is easy, problems can arise here too. Almost all of them can be dealt with quickly with suitable countermeasures.



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