01 Laser-Arc Composite Welding of Thick Plates
Thick plate (thickness ≥ 20mm) welding in aerospace, marine vessels, rail transportation and other important areas of large equipment manufacturing plays a key role. These components are usually characterized by large thickness, complex joint forms and service environments. Welding quality has a direct impact on the performance and life of the equipment. Traditional gas shielded welding methods have challenges such as low welding efficiency, high energy consumption and high residual stresses due to slow welding speeds and serious spattering problems, making it difficult to meet the ever-increasing manufacturing requirements. However, laser-arc composite welding technology is different from traditional welding technology in that it successfully integrates the advantages of laser welding and arc welding, and is characterized by a large depth of fusion, fast welding speed, high efficiency, and better weld quality, as shown in Figure 1. Therefore, this technology has attracted widespread attention and has begun to be applied in some key areas.
02 Thick plate laser-arc composite welding research
Norwegian Institute of Industrial Technology and the Swedish Lule University of Science and Technology for 45mm thick microalloyed high-strength low-alloy steel, the study of the 15kW case of composite welded joint organization uniformity. Osaka University and the Egyptian Central Institute of Metallurgy using 20kW fiber laser, to carry out a thick plate (25mm) single-pass laser - arc composite welding process research, using the bottom of the bottom liner to solve the problem of the bottom hump. Denmark Force Technology company used two 16 kW disc laser in series to carry out the 32kW case of composite welding 40mm thick steel plate process research, indicating that high-power laser - arc welding is expected to be used in offshore wind power tower welding, as shown in Figure 2. Ha welding in the first to master the high-power solid laser - fused electrode arc composite heat source welding core technology and equipment integration technology, the first successful high-power solid laser - dual-wire fused electrode arc composite welding technology and equipment for China's high-end equipment manufacturing industry.
According to the thick plate laser - arc composite welding at home and abroad research status can be seen, laser - arc composite welding method and narrow gap bevel combination can realize the welding of thick plate. When the laser power is increased to more than 10,000 watts, under the irradiation of high-energy laser, the vaporization behavior of the material, the interaction process between the laser and plasma, the steady state of the molten pool flow, the heat transfer mechanism, and the metallurgical behavior of the weld seam will undergo different degrees of change. With the increase in power to more than 10,000 watts, the increase in power density will increase the degree of vaporization in the region near the small hole, bringing the recoil force directly affects the small hole and the stability of the molten pool flow, thus bringing about a change in the welding process, the implementation of the laser and its composite welding process has a non-negligible impact. These characteristics of the welding process phenomenon in a certain degree directly or indirectly reflect the stability of the welding process, and can even determine the quality of the weld. The coupling effect of the two heat sources, laser and arc, can make the two heat sources give full play to their own characteristics, to obtain better than a single laser welding and arc welding welding effect. Make the welding method and laser self-melting welding method compared with the gap adaptability and weldable thickness and other advantages, compared with the narrow gap laser filler wire welding method for thick plate has a high wire melting efficiency and good bevel fusion effect and other advantages. In addition, the laser's attraction to the arc enhances the stability of the arc, making the laser-arc hybrid welding faster than the traditional arc welding and laser filler wire welding, with relatively high welding efficiency.
Laser-arc Hybrid Welding
03 High Power Laser-Arc Hybrid Welding Applications
High-power laser-arc composite welding technology has a wide range of applications in the marine industry. Germany Meyer shipyard to establish 12kW CO2 laser - arc composite welding production line, for the hull of the flat plate and reinforcing bar welding, to achieve 20m long fillet weld forming, the degree of deformation is reduced by 2/3. GE developed fiber laser - arc composite welding system, the maximum output power of 20kW, welding the U.S. Sara toga aircraft carriers, saving 800 tons of weld metal, reducing 80% of man-hours. 80% of the labor time, as shown in Figure 3. CSBC 725 adopts 20kW fiber laser high-power laser-arc composite welding system, which can reduce welding deformation by 60% and increase welding efficiency by 300%. Shanghai Waigaoqiao Shipyard adopts 16kW fiber laser high-power laser - arc composite welding system, the production line adopts the laser composite welding + MAG welding new process technology, to achieve the 4-25mm thick steel plate welding single-sided single-pass welding double-sided molding. High-power laser - arc composite welding technology in armored vehicles have a wide range of applications, its welding features: large thickness of complex metal structure welding, lower cost, high efficiency manufacturing.
High-power laser-arc composite welding technology has been initially applied in a number of industry sectors, and will become an important means of efficient manufacturing of large structures with medium and large wall thickness. At present, there is a lack of research on the mechanism of high-power laser-arc composite welding, which needs to be further strengthened, such as the interaction between the phototropic plasma and the arc and the interaction between the arc and the molten pool. High-power laser - arc composite welding process still exists in many unresolved issues, such as narrow process window, weld organization and mechanical properties of non-uniformity, welding quality control is more complex. With the gradual increase in industrial-grade laser output power, high-power laser - arc composite welding technology will develop rapidly, a variety of new laser composite welding technology will continue to emerge. Localization, large-scale, intelligent will be the future development of high-power laser welding equipment is an important trend.
