Laser welding by hand is used more frequently in industrial processes because it has wider application than traditional welding as less heat is created because the beam is so focused. This means that heat transfer to the workpiece is much less and the metallurgical structure is less affected and the quality of the weld is much higher than with traditional forms of welding.
The laser pulse waveform is an important problem in laser welding, especially for sheet welding. When the high-intensity laser beam strikes the material surface, 60~98% of the laser energy will be reflected and lost on the metal surface, and the reflectivity will change with the surface temperature. During a laser pulse, the reflectivity of metal changes greatly.
Power density is one of the most critical parameters in laser processing. With higher power density, the surface layer can be heated to boiling point in a microsecond time, and a large amount of vaporization is produced. Therefore, high power density is beneficial to material removal processing, such as punching, cutting, and engraving. For lower power density, it takes several milliseconds for the surface layer temperature to reach the boiling point, and before the surface layer vaporizes, the bottom layer reaches the melting point, which is easy to form good fusion welding. Therefore, in conducting laser welding, the power density ranges from 10 4 to 10 6 W/cm 2.
Pulse width is one of the important parameters of laser welding by hand. It is not only an important parameter that is different from material removal and material melting, but also a key parameter that determines the cost and volume of processing equipment.
There is no need to use electrodes, and there is no concern about electrode pollution or damage. And because it does not belong to the contact welding process, the wear and deformation of handled fiber laser welding machines and tools can be minimized.
The laser beam is easy to focus, align, and be guided by optical instruments. It can be placed at an appropriate distance from the workpiece and can be re-guided between machines or obstacles around the workpiece. Other welding rules cannot be used because of the above space restrictions.
The heat input can be reduced to the minimum required amount, the metallographic change range of the heat-affected zone is small, and the deformation caused by heat conduction is also the lowest.
The laser beam can be focused in a small area and small and closely spaced parts can be welded.
The workpiece can be placed in a closed space (under the control of vacuuming or an internal gas environment).
When welding thin materials or small-diameter wires, there will be no trouble of reflow like arc welding.
There is a wide range of weldable materials, and various dissimilar materials can be joined with each other.
No vacuum or radiation protection is required.
It is not affected by the magnetic field (arc welding and electron beam welding are easy), can accurately align the weldment.
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