subject: Laser Processing of Metals [print this page] You may have known that lasersproduce very powerful and exact beams of light. As a result, they can be used as very useful tools in ordinary to the most sophisticated metal processing.
The cutting process: The laser cutting of the materials is a common application of the laser systems. As the laser beam is focuses on the metal piece the energy is absorbed and transformed into heat. The power density required to cut a metal piece or metal sheet. The heat locally provokes to a quick increase of the temperature of the piece, the fusion and or the vaporization of the interaction zone determine the formation of a cut. Laser cutting leaves with an edge having a high-quality surface finish.
The Welding process: When a low power density laser is employed the laser energy is deposited on the surface of the metal and the heat is transported to the inside by means of a mechanism of heat conduction to conduct welding process. Higher power densities, however, involve the direct ionization mechanism to melt the metal piece. The laser beam can be transmitted through air rather than requiring a vacuum, the process is easily automated with robotic machinery, x-rays are not generated, and LBW result in higher quality welds.
The drilling process: Like other metal processing operations, drilling is accomplished by melting and or vaporization (ablation) of metal piece through absorption of energy from a focused laser beam. As the energy required to melt the metal piece is very low compared to in vaporization process, melting is generally favored. The pulse duration and power density determines whether melting or vaporization will take place. Vaporization of a metal takes place when pulse duration is too small however melting takes place when pulse duration is larger, when a flash-lamp pumped laser is used. A Q-switched laser normally has pulse duration in the order of nanoseconds, peak power and a material removal rate of a few micrometres per pulse. While a flash lamp pumped laser normally has a pulse duration on the order of hundreds of microseconds to a millisecond, peak power in the order of sub, and material removal rate of ten to hundreds of micrometers per pulse.
The Surface Treatments: Lasers offer unparallel control on the surface to obtain various structural effects compared to other surface etching processes. However, the technique is complex and often a computer system is employed to drive the movements of the laser head. Despite this complexity, very precise and clean microstructures and engravings can be achieved at a high rate. The process requires the shorter wavelength of laser beam than the traditional 10,640nm wavelength CO2 laser. The ytterbium fiber laser is usually employed with a lasing medium at 1,064nm wavelength, or its harmonics at 532 and 355nm.
