As the types of welding materials become more and more abundant, customers have higher and higher requirements for welding quality. There are many factors that affect the quality of laser welding, such as the type of shielding gas, the size of the gas flow, the motion control method and the accuracy. Among the many influencing factors, fiber laser is the key factor to ensure good welding quality. There are many factors that affect the welding quality of the laser, such as laser power, welding speed, defocus, etc., but the factor of beam mode is often ignored.
The beam modes of fiber lasers are divided into single mode and multimode. In welding applications, the focused spot has a great influence on the weld penetration and indirectly affects the tensile strength of the weld. The core of single-mode laser is relatively thin, and the beam quality is better than that of multi-mode. The laser energy has a Gaussian distribution with the highest energy density in the middle. The three-dimensional image is a sharp round mountain peak, as shown in the upper two images. The core of the multimode laser is thicker than that of the single mode, and the beam quality is worse than that of the single mode. The energy distribution is more average than that of the single mode. The three-dimensional image is an inverted cup, as shown in the bottom two pictures.
With a certain laser power, as the welding speed decreases, whether single-mode or multi-mode lasers are used, the weld penetration will gradually increase.
In the case of a certain laser power, as the defocusing amount decreases, whether single-mode or multi-mode lasers are used, the weld penetration will gradually increase.
When the power, defocus and speed remain unchanged, the welding penetration of single-mode lasers is larger than that of multi-mode lasers.
Different laser beam modes need to be matched with different process parameters to achieve the best welding effect.