Jan 27, 2019
Power density Power density is one of the most critical parameters in laser processing. Using a high power density, the surface layer can be heated to boiling point over a microsecond time range, resulting in a large amount of vaporization. Therefore, high power density for material removal processing, such as punching, cutting, carving favorable. For the lower power density, the surface temperature to reach the boiling point needs to go through a few milliseconds, before the surface vaporization, the ground floor to reach the melting point, easy to form a good melting welding.
Therefore, in conductive laser welding, the power density is in the range of 104~106W/cm2.
Pulse Waveform Pulse waveform is an important problem in welding, especially for sheet welding. When the high-strength beam hits the surface of the material, the metal surface will have the energy reflected and lost, and the reflectivity changes with the surface temperature.
During the action of a pulse, the reflection rate of metal varies greatly.
Pulse width is one of the important parameters of pulse welding, which is not only an important parameter which is different from material removal and material melting, but also a key parameter to determine the cost and volume of processing equipment.
Effect of defocusing Amount Because the power density of the spot center at the laser focal point is too high, it is easy to evaporate into holes. The power density distribution is relatively uniform on each plane leaving the laser focus. There are two types of defocusing: positive defocusing and negative defocusing. The focal plane is located above the workpiece for positive defocusing, and vice versa for negative defocusing. According to the theory of geometric optics, when the positive and negative defocusing plane is equal to the weld plane distance, the power density on the corresponding plane is approximately the same, but in fact the shape of the melting pool obtained is different. When negative defocusing, a greater melting depth can be obtained, which is related to the formation process of the melting pool.