Laser cutting and laser welding
Laser cutting and laser welding have established themselves as effective, fast and cost-efficient methods for material processing in numerous industries. These process technologies are used in the automotive, airplane and shipbuilding industry as well as in the semiconductor industry and in medicine. In laser welding, the light is concentrated on one focal spot (Ø 0.2 - 0.3 mm) by means of a focusing optic and the material to be welded is melted quickly thanks to the high energy density. Once the melting point of the material is reached, it evaporates and a vapor canal is created. This is called a keyhole. Around the vapor canal, a melting zone forms in this method. When the laser beam and the workpiece move towards each other, the melted material runs directly behind the laser into the vapour canal and a clean weld is formed. Since this entire process only takes fractions of a second, a very high speed can be achieved in laser welding.
Keyhole welding and 3D laser welding with high laser intensity
In keyhole welding, the material being processed can be almost completely penetrated with the laser’s high energy. The intensity of the laser beam is above the limit of 10 6W/cm2 and its energy ensures that the mixture of evaporated material and shielding gas ionises resulting in laser-induced plasma. In heat conductivity welding, the intensity of the laser beam is below the threshold of 10 6W/cm2 . In this method, metal plasma is formed and there is no deep welding effect. 3D laser welding and cutting is suitable for processing 3D components, profiles or pipes. Even in places that are difficult to access, exact cuts and clean weld seams in high quality are produced. The material-friendly processing reduces follow-up operations and increases the degree of automation. An important argument for laser welding is the high laser welding speed which can guarantee work at a high level.
Which operating or protective gases are used for laser welding?
Depending on the application, different laser gases can be used for laser welding. Due to the better reproducibility, more and more ready-mixed resonator gases are used in the industry. Among the most popular gases are CO2 4.5, N2 5.0 (nitrogen gas for laser cutting), helium for laser welding 4.6 and argon gas for laser welding 4.6.
3D printing involves the use of a variety of gases at different stages of the production chain.The latter essentially begins with the production of the powders used in 3D printing. Metallic powders are atomized with a gas jet to give them their spherical shape. Plastic powders, by contrast, undergo a cryogenic grinding process. This involves the use of liquid nitrogen. To guarantee their quality, some powders have to be permanently stored in a shielding gas atmosphere. Special containers filled with shielding gas are used for this purpose.
Depending on the specific process, printing a component involves the use of shielding gases, carrier gases and/or cooling gases. In the majority of printing processes, the type of gas required – and its purity – depends on the material. The following table provides an overview of possible shielding gases. Gases are also needed for subsequent treatment of components. This is done either through subsequent heat treatment designed to achieve homogeneous component properties or by carrying out a subsequent sintering process. Stress relieving annealing, a process that requires the use of a shielding gas, is the typical heat treatment. But other types of heat treatment may also be required.
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