Today we are going to be learning about the main causes of pinholes from laser welders. Have you ever heard of laser welding? It’s not common, but it doesn’t mean that it doesn’t exist. To be exact, it is referred to as Laser Beam Welding or LBW for short. We’ve never talked about this type of welding process so allow me to define it. As we know, welding is a process or an art of joining together two or three pieces of metal with the use of heat, electricity, or fire. In laser welding, that’s also the goal – to join multiple pieces of metal but through the use of a laser. This laser beam will be able to provide a concentrated heat source that allows narrow and deep welds at high welding rates. Sounds good? This process is uncommon, since it is usually used in high volume applications like in the automotive industry.
How exactly does laser beam welding work? Laser beam welding has a high power density that can result in small heat affected zone with high heating and cooling rates. The size of the zone can vary between 0.2mm and 13 mm. Keep in mind though that only smaller sizes are used for welding. As I said above, laser welding allows deep welds which really depends on the location of the focal point. You can maximize the penetration if your focal point is slightly below the surface of the work piece. With laser welding, you will be able to weld carbon steels, HSLA steels, stainless steels, aluminum, and titanium.
Since laser welding is used in the automotive industry, welders put great importance when it comes to detection and prevention of welding defects like pinholes. The good thing about laser welding is that the carbon dioxide penetration that can be found in this process is characterized by the formation of an electron-free plasma, whose radiation can be measured to be able to detect the defects. That makes it a little easier right? The most common defect that can appear during the laser welding process are holes, porosity, spattering, drop-outs, and lack of penetration.
Today we are going to be concentrating on holes and porosity.
The main causes of the appearance of the said faults – including pinholes could be sure to the high speed carbon dioxide laser welding process. It may be due to the state of the cross section of the specimen, the gap, the flow rate of the shielding gas, the travel speed, and the laser power. As a welder, you must be attentive to all the little details. You must also take note of the shape of the weld bead since it is an important factor that helps in determining the strength of the work piece.
However, it is understandable that you might miss the little signs and little hiccups in the system while you are welding. Automotive industry is quite busy and hectic. Most companies have developed a monitoring system that is able to detect weld defect and bead defects in real time. With this, you will be able to prevent the occurrence of defeats, reduce the loss of material, and also guarantee good quality for your customers. It’s a great thing to invest in if you have the capital or the money, but if you don’t, you can still prevent them by paying extra attention to the little things.
Here are different ways in which companies are able to detect the defects:
1.) Acoustic Emission
2.) Optic Signals
3.) Image Processing
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