Views: 134 Author: Site Editor Publish Time: 10-04-2021 Origin: Site
Laser welding is an efficient and precise welding method that uses a high-energy-density laser beam as a heat source. Laser welding machine has now developed into one of the important aspects of the application of laser material processing technology. There are two basic modes of laser welding: laser deep penetration welding and other heat conduction welding. Among them, laser deep penetration welding is more and more widely used. The following Leapion Laser will share with you what factors will affect the welding effect of laser welding deep penetration.
Deep penetration, or deep penetration welding. It is common to weld thicker materials with high laser power. In deep penetration welding, the lasers are focused together to create a very high power density on the workpiece.
In fact, the part where the laser beam is focused will vaporize the metal, causing a blind hole (ie, deep penetration hole) to appear in the molten metal pool. The metal vapor pressure will block the surrounding molten metal, so that the blind hole is always open during the welding process.
The laser power is mainly absorbed by the melt at the boundary between the vapor and the melt and the wall of the deep penetration hole. The focused laser beam and the deep penetration hole continue to move along the welding track. The welding material melts in front of the deep penetration hole and resolidifies at the back to form a weld.
The prerequisite for deep penetration welding is to focus the laser spot so that it has a sufficiently high power density, so the laser power density has a decisive influence on the weld formation. The laser power controls the penetration depth and welding speed at the same time. For a laser beam with a certain diameter, when the laser power is increased, the penetration deepens and the welding speed increases.
Generally, there is a critical value for the laser power that reaches a certain welding penetration. When this critical value is reached, the molten pool will boil violently, and when it exceeds, the penetration will decrease sharply. In addition, due to the force of the metal vapor, small holes are formed in the molten pool, and the small holes are the key to the realization of deep penetration welding.
The focal spot power density is not only proportional to the laser power, but also related to the laser beam and focusing optical path parameters.
In the process of deep penetration welding, the welding speed is inversely proportional to the penetration depth. In the case of keeping the laser power constant, such as increasing the welding speed, the heat input will decrease and the penetration depth will also decrease. Therefore, appropriately reducing the welding speed can increase the penetration depth, but too low a speed will lead to excessive melting of the material and the phenomenon of weld penetration of the workpiece. Therefore, for a specific laser power and a specific thickness and type of material, there is a suitable welding speed range to obtain the maximum penetration.
In deep penetration welding, in order to maintain sufficient power density, the focus position is very important. The change of the relative position of the focal point and the surface of the workpiece directly affects the width and depth of the weld. Only when the focal point is located at a suitable position on the surface of the workpiece, the resulting weld can form a parallel section and obtain the maximum penetration depth.
The protective gas has two functions:
1) Exclude the air in the welding area to protect the working surface from oxidation;
2) Suppress the plasma cloud generated during high-power laser welding.
The gap between the work pieces and the assembly gap are directly related to the penetration depth of the welded work piece and the width of the weld seam. In deep penetration welding, if the joint gap exceeds the spot size, it cannot be welded; if the joint gap is too small, sometimes the process will produce undesirable effects such as overlapping of the joint plates and difficulty in fusion; if the joint gap is too large, it is easy to weld through; slow speed Welding can make up for some welding seam defects caused by excessive gaps, while high-speed welding has narrower seams and stricter assembly requirements.
The absorption of laser by the material of the workpiece to be welded determines the efficiency of laser welding. There are two factors that affect the absorption rate of the material to the laser:
1) Material resistivity. After measuring the absorptivity of the polished surface of different materials, it is found that the laser absorptivity of the material is proportional to the square root of the resistivity, and the resistivity changes with the change of temperature;
2) The surface state of the material has an important influence on the beam absorption rate, which has a significant effect on the welding effect.
It can be seen that the above six factors directly affect the welding effect of laser welding deep penetration, we should pay more attention to the process of using laser welding machine. For more professional questions about laser welding machines, welcome to consult Leapion Laser.
