You might not realise it, but the modern world wouldn’t be where it is now without welding. Our heavy reliance on this economic and efficient process has allowed us to continue building taller skyscrapers, more innovative road vehicles, more ambitious ships, bridges… Almost anything made from metal will require welding at some stage. Fact
Welding doesn’t discriminate against who can become a welder, in fact, the industry is very welcoming and barriers of entry are low. Welding does, however, judge the quality of welds, don’t forget that the main objective of welding is to guarantee resistance to the stress the weld is intended to withstand.
To the naked or inexperienced eye, the difference between a good weld and a bad weld can be hard to spot. It is also important to understand that the quality of a weld can not be determined only by a visual inspection, and further tests and analysis are required. However, some details of the weld that can be seen with the naked eye can help us to make a first evaluation of the joint’s quality, let’s take a look at some of them.
Strength, Quality and Selection
The resistance of our weld is directly linked to the quality in which it was performed. The quality control is structured in three phases:
- Before the weld is performed, all the technical details must be reviewed to make sure that they are compliant with the technical and quality requirements.
- During the welding processes, all the parameters must be checked
- After the weld, different quality tests are performed
Since there are so many types of welding processes, each of them has its own set of defects and features that should be analysed to determine its quality. Welders tend to say that a weld shouldn’t be defined as “good or bad”, a better definition would be: “conforming or not conforming to the reference parameters and standards”. This is because a visually “bad” weld can be perfectly compliant to the goal it was designed to match, as well as a visually “good” weld can be rejected with further tests against it.
The truth is that every weld needs to be assessed on a case by case basis and if it isn’t strong enough and the finish isn’t of high quality, something went wrong and need to be fixed.
With this being said, what are the main features that we should look for when determining the quality of a weld with a visual test (VT)?
MIG Welding
Metal Inert Gas Welding, or MIG Welding for short, is often used for large industrial projects. This means that the welds bear a lot of responsibility, and so the welder using the welding gun to join the metal pieces must ensure that they are doing a top-notch job.
What defects should be analysed to determine the quality of a MIG weld with a visual test?
1. Lack of penetration to the root (when it is possible to see the back of the cord).
2. Bite on the edge of the junction
3. Lack of fusion at the edges
4. Surface cracks
5. Overlapping of the deposited metal on the base metal
6. Over thickness of deposited metal
7. Penetration excess (when it is possible to see the backside of the bead).
Most of these defects can be addressed following the WPS correctly, and making sure the physical parameters are correct and all the equipment is properly cleaned and ready.
TIG Welding
Tungsten Inert Gas Welding, or TIG Welding as most welders will refer to it, is commonly used in aerospace engineering, the automotive industry, and construction. For these reasons, it literally protects lives, and so must be applied with the utmost care and quality. It is considerably more difficult to do well than MIG Welding, and so it comes with additional responsibilities and quality control. You may also see TIG referred to as GTAW – Gas Tungsten Arc Welding.
The biggest problem with TIG welds is that they are deceptively good looking, and require an experienced and educated eye to spot the problems.
Here’s what they should be looking out for:
1. Lack of penetration to the root (when it is possible to see the back of the cord).
2. Bite on the edge of the junction
3. Lack of fusion at the edges
4. Surface cracks
5. Rusty root
SMAW Welding
Finally, we have SMAW Welding (Shielded Metal Arc Welding) or, which you might also sometimes see referred to as Stick Welding MMA (Manual Metal Arc Welding). In terms of ease, this is a great type of welding for beginners and it works with all sorts of metals. Unfortunately, that same ease of use and versatility that makes it accessible to beginners is also what exposes it to the most risks of being carried out in a low-quality manner.
Pay close attention and even consider making a checklist for the next time you do a stick weld:
1. Bite on the edge of the joint. 2.
2. Slag inclusion
3. Lack of fusion at the edges
4. Surface cracks
5. Projections on the base metal and weld joint.
How does Soldamatic increase the quality of the welds?
Traditional welding training has been stagnant for too long, and new technologies like Augmented Reality are leading the development of the next industrial generation of skilled workers.
Thanks to the AR technology, Soldamatic allows training without using materials and consumables, giving trainees the extra training they may require. After the weld is performed, Soldamatic provides a full in-depth analysis of the weld performed, letting the trainee understand the mistakes and review the practice anytime.
Would you like to see how it works?
Conclusions
Even though a visual tests is a fundamental test that is always performed after welding, it shouldn’t be the only test to determine the quality of a weld. We need to analyse each weld in a case by case basis, and also minding the differences among the different welding processes.
However, these are some advices that could help you to perform a high-quality weld:
- Follow all the parameters determined by the WPS
- Make sure the pieces are properly fitted before performing the weld
- Clean the bevels and make sure all the equipment is ready to be used
