Welding defects include any flaws that compromise the quality of the weld. They can be defined as occurring any time there is a deviation in the size and shape of the metal structure that affects technical and design requirements.
A defect can occur at any stage of the welding process. They can be either internal or external. Internal defects are not visible. They include defects such as slag inclusion, incomplete penetration, and incomplete fusion.
External defects are more easily detectable because they can be seen on the metal surface itself. They include cracks, undercuts, porosity, spatter, and overlaps. Let’s take a look at some of these external defects.
External Welding Defects
Cracks are the most common welding defect. There is almost no way a weld can meet any standard if it has a crack. Two different types of welding cracks are hot cracks and cold cracks.
- Hot cracks. These cracks can occur during the welding process when the process uses intensive heat, generally when the temperature rises to more than 10,000 degrees Celsius (18,032 degrees Fahrenheit). They can also occur during crystallization when the weld has used high temperatures.
- Cold cracks. These appear a few hours or days after the weld is complete during the cooling down or solidification process. They are most common when welding steel and generally because the steel itself is deformed.
How to prevent cracks. The primary ways to prevent either hot or cold cracks are:
- Preheat the metal.
- Use proper joint design.
- Use appropriate metal.
- Use proper amperage settings.
- Avoid rapid cooling of the weld area.
Undercuts appear as a groove formation at the weld toe closest to the edge. It results in a weakened weld, which is never ideal.
Undercuts are often the result of using a welding speed that is too fast, too high of a voltage, an electrode that is too large, use of the wrong filler metal, incorrect usage of shielding gas, and poor welding technique.
How to prevent undercuts. You can prevent undercuts by:
- Choosing the correct shielding gas.
- Use the correct welding speed. If too fast or too slow, undercuts can occur.
- Use the proper current.
- Use the right size of electrode—not too large.
Porosity occurs when gases or air bubbles get trapped in the weld metal. It occurs when the weld metal has been contaminated and results in a weak weld that may collapse over time.
How to prevent porosity. There are ways to prevent porosity, for example:
- Clean all the materials before you begin including the weld surface.
- Before you begin, make sure the welding zone is free of moisture.
- Slow the welding process. A lower travel speed allows the gases to escape.
- Use the correct electrode size and position it at the current angle between 30 and 45 degrees.
Spatter occurs when metal particles from the weld get stuck on areas around the weld area. It most often occurs in gas metal arc welding. It can be difficult or impossible to remove the particles.
How to prevent spatter. Most experts say spatter cannot be completely eliminated, but it can be kept to a minimum by:
- Thoroughly cleaning all surfaces before beginning the welding process.
- Cleaning the entire welding area before beginning.
- Making sure the voltage setting is not too low.
- Making sure the arc is not too long.
- Use proper polarity.
- Use proper gas shielding.
An overlap occurs when the weld pool overflows onto the surface of the metal that is being welded. The molten metals do not fuse with the base metals. This is often caused by using a current that is too high or an arc that is too long.
How to prevent overlaps. Prevention of overlaps includes paying close attention to get it right the first time. Some prevention techniques include:
- Employing the right welding technique for the metals you are trying to weld.
- Using a low welding current.
- Using the electrode at the correct angle.
- Use the correct welding arc.
Arizona’s Leader in Welding Supplies Can Help with All of Your Welding Issues
Vern Lewis Welding Supply has eight locations throughout the state of Arizona and we maintain a complete supply of products needed for successful welding. The professionals at Vern Lewis can help you choose the proper tools and answer any questions you may have.
In addition to providing tools and supplies, Vern Lewis Welding also offers welding training. For more information, contact us online or call 602-633-7481.