Analysis of laser welding parameters

The parameters that directly affect the quality of laser welding include: laser pulse energy, laser beam spot diameter, laser pulse frequency, laser pulse width, laser pulse waveform, relative light absorption rate of the welded material, welding speed, protection Gas etc.

　　The energy of the laser pulse

　　 refers to the maximum output energy of a single laser pulse, the unit is J (joule). This is a main parameter of the laser, which determines the maximum energy that the laser can produce. According to the purpose of mold repair, the laser energy below 70J can already meet the needs of any occasion, and no matter how large the energy is, it is wasted or fundamentally It is not available, and the volume of the laser power supply and the volume of the radiator continue to increase, which reduces the efficiency of the power supply.

　　 Laser spot focus diameter

　　 This is an extremely important parameter that reflects the design performance of the laser. The unit is (mm), which determines the power density and processing range of the laser. If the optical design of the laser is reasonable and advanced, the laser energy is concentrated, and the focus is accurate, the laser spot diameter can be controlled within the range of 0.2mm-2mm, and whether the focus diameter of the laser can be controlled within 0.2mm is a strict requirement for the laser generator. test. Generally speaking, the domestic laser design only wants to reduce the cost. Therefore, the laser device is simple in processing and the design is not rigorous. The laser diverges seriously in the resonant cavity, which makes it difficult to focus accurately. The laser spot diameter of the laser does not meet the standard at all. The weighing is 0.2mm, but the minimum can only reach 0.5mm, and due to the divergence of the laser, the output laser beam cannot be in a regular circle, which causes the actual laser irradiation area to be too large, and the phenomenon of ablation of the weld appears. That is, unnecessary laser irradiation occurs at both ends of the weld, which makes the two ends of the weld appear concave. This phenomenon has a particularly serious impact on repairing the polished mold, and sometimes even makes the mold scrap. Tongpu's lasers are well-designed, strictly selected materials, and carefully adjusted, so that the diameter of the beam spot output by the laser can be precisely monitored, so that the minimum focus spot size can reach 0.2mm, and it can be in the range of 0.2mm and 2mm. Carry out stepless adjustment to reach the international advanced level.

　　 Laser pulse frequency

　　 This is the ability to reflect how many pulses the laser can produce in one second, and the unit is (Hz). The first thing that needs to be explained is that the welding metal uses the energy of the laser, and when the laser power is constant, the higher the frequency, the smaller the energy output of each laser. Therefore, we need to ensure that the energy of the laser is sufficient to melt the metal. In the case of, considering the processing speed, the output frequency of the laser can be determined. In the case of laser repairing abrasive tools, 15Hz can already meet the needs of welding. Too high frequency will inevitably cause the pulse energy of the laser to be too low, resulting in welding failure.

Laser pulse waveform

　　 For the welding process using pulsed laser, the laser pulse waveform is an important issue in pulsed laser welding. When a high-intensity laser is incident on the surface of the material, the metal surface will reflect 60% to 98% of the laser energy, and the reflectivity changes with the surface temperature. Therefore, different metals have different laser reflectivity and laser utilization. To perform effective welding, lasers with different waveforms must be input, so that the metal structure at the weld can be crystallized in the best way and formed into a matrix. A consistent structure of the metal can form a high-quality weld. Domestic general machines use cheap single-wave laser power sources. Therefore, their welding flexibility is low, and it is difficult to adapt to the welding of multiple mold materials, and they are often reworked, which greatly wastes the time of welding materials and may cause mold damage. scrapped. The reflection and absorption of the laser on the surface of different metal materials are very different, and the same beam of laser will produce different welding effects on different metals, and affect its penetration, welding speed, crystallization speed and hardness, so a single rectangular wave Welding cannot solve the requirements of different mold metal welding. Tongpu TPM intelligent laser mold repair welding machine adopts domestic unique intelligent waveform technology to achieve a high degree of flexibility of the laser welding system. The waveform can be adjusted according to different applications, so that the metal structure of the weld is consistent with the base metal. The mold or After the metal parts are welded and repaired, the weld seam hardness reaches HRC50-HRC58, which truly achieves non-destructive welding and greatly improves the quality of repair welding.