The welding process is as much art as science, and some features or techniques are heavy on the art display. There is uniformity in the standard welding practices, but signatures can be evident in techniques. Since signatures shine through ripples in welding, what is it?
Ripples in welding are an artifact of the process formed after the molten pool is solidified. They are more pronounced in some welding processes like Tungsten Inert Gas (TIG) than in others. Different materials also display ripples in varying ways.
This article describes ripple in welding and welding defects, and I also explore the differences between discontinuity and defect and how to test for welding defects.
How Does Bead Welding Work?
Bead welding is a basic welding technique that involves drawing a filler material across a welding surface, and bead welds or weld beads result from this process.
This type of weld is often the first form of welding people learn, and different types exist based on how much oscillation you use when the filler material is applied to the surface.
When you use more oscillation—a wider application of filler material—a weave bead results, and less side-to-side oscillation results in narrower stringer beads. In bead welding, you apply the filler material between two or more pieces of metal, and when it cools, it forms a strong bond between the two surfaces.
Sometimes, if a welding process is too hot, bead ripples occur and may cause longitudinal weld cracks. Bead ripples are undulations with measurable height differences that appear along the length of the weld bead.
A weld bead ripple can be desired in some applications, like in certain coated steel products in which they ensure that all contaminants from the weld area have been squeezed out. This prevents the occurrence of potential occlusions and the resultant compromise in weld quality.
What Is Ripple in Welding?
Ripple in welding is the weld profile of the molten weld pool that solidifies as you weld the joint along. To paint a picture, imagine a wave lapping against a shore, but rather than ebbing back, each wave solidifies.
Although many people believe each ripple is a bead, this is not true. A weld bead is an entire series of ripples, and not only one. Two types of ripples are:
- Loose ripples have more peaks and valleys.
- Tight ripples have a smoother surface.
What Are Welding Defects?
Welding defects are imperfections or flaws that compromise the intended use of the weldment. They are classified according to ISO 6520, while ISO 10042 and ISO 5817 specify the acceptable limits of discontinuities.
A weld not only needs to be strong for its intended purpose, but it must also be aesthetically pleasing, thus, most weld defects either make the weld look unpresentable or weaken it. Welding defects are majorly grouped into two:
- Internal welding defects occur under the surface of the weldment.
- External defects occur on the upper surface of the weldment.
Here are further types of external defects:
- Incomplete fusion or lack of fusion—either at the face of the previously deposited strand or joint edge
- Undercut—a notch at the foot of the cord.
- Slag inclusions—the retention of solid materials within the weld metal.
- Incomplete penetration or lack of penetration—the root of the weld bead doesn’t reach the joint’s root.
- Spatter—molten particles are projected from the weld bead.
- Porosity—formation, and retention of gas bubbles within the melt zone of the welding materials.
- Cracks—usually appear in the Fused Zone or Heat-Affected Zone.
- Burn through—the weld material penetrates the base parts.
- Overlap—the weld face extends far over the weld toe.
Following the basics of welding can help you avoid making these defects and some of the primary considerations include:
- Use the correct sizes of electrodes.
- Find and maintain the right torch angle.
- Maintain a proper arc length.
- Ensure the base metal is clean and free from contaminants.
- Set the correct voltage and amperage.
Discontinuity Vs Defect
A welding discontinuity or weld imperfection refers to an interruption in the standard physical structure of a material that changes its properties. It is an interruption of normal flow, and you can easily recognize a discontinuity. A simple variation of properties doesn’t indicate a discontinuity
Discontinuities occur due to wrong welding techniques patterns; you should avoid making them and fix them when they occur. You can see a discontinuity in the weld bead’s thickness, shape, and even quality.
A group of weld discontinuities may become a weld defect if they exceed the tolerance limits stated in your project. Your country code, the type of environment you are in, and the material you are working with set the limits.
Depending on its applications, a weld with a specific crack can be approved or disapproved for use.
How Do You Test for a Welding Defect?
After making a weldment, it is crucial to test the product to ensure its quality and durability. If you don’t detect the defects on time and the product is used, any collapse due to the faulty welded product can lead to loss of lives and property. Welding inspection and testing are split into two categories:
- Destructive testing (DT)
As a cheaper inspection method, it features in mass production where one or two components can be sacrificed for testing. It is ideal as a training tool during training courses because it is often easier to understand than other testing methods, and students can do much testing at a minimum cost.
The two most common destructive tests used in training courses are Root and Face bend Testing and Macro Etch Testing.
- Non-destructive testing (NDT)
Non-destructive testing provides the opportunity to test and prove the absence of defects without putting the welded structure at risk or compromising the welded part. During the manufacturing, construction, assembly, and maintenance stages, you can perform these tests.
Some NDT testing methods are simple to understand, are done with minimal equipment, and include dye penetrant testing. Other methods require expensive equipment and specialist operators and include x-ray testing. Common testing methods are Magnetic particle testing, X-ray testing, Ultrasonic testing, etc.
With proper application, non-destructive tests offer benefits by saving time, reducing cost, reducing equipment failure rates, improving the quality and reliability of industrial equipment, etc.
