The blue laser, as a new direction in the field of semiconductor lasers, has significantly improved the absorption rate of colored metal materials such as copper, gold, and aluminum by several to tens of times compared to near-infrared wavelength lasers. With the increasing demand for high-quality laser manufacturing in the industry, high-performance blue light sources are gradually being applied in material forming fields such as welding, heat treatment, and additive manufacturing with broad market prospects. This article analyzes the advantages of high-power and high-brightness blue lasers in the field of material processing, summarizes the development history of blue semiconductor lasers and their current applications in metal processing fields, and puts forward some thoughts on the future development direction of high-power blue lasers.
Semiconductor laser is a kind of electro-optical conversion device, which has achieved rapid development and fruitful results in the past 50 years, and has wide penetration and application in scientific research and engineering technology. It uses the semiconductor material as the gain medium, through the principle of electrons in the transition between the energy levels of light, the use of the resonant cavity composed of semiconductor crystals and parallel mirrors, under the electric injection to achieve light oscillation, feedback, and finally produce light radiation amplification, so as to achieve laser output.
As a new direction in semiconductor laser field, blue laser has developed many applications rapidly in recent years. Among them, thanks to the unique advantages of the 450nm short-wave segment, compared with near-infrared wavelength lasers, the absorption rate for non-ferrous materials (especially copper and gold) has been increased by several times to tens of times. High-performance blue light source provides a new technology for high-quality laser processing of non-ferrous metal materials such as copper and gold, and also makes this technology can be widely used in the national economy and military defense fields such as material processing, consumer electronics, automobiles and new energy, and has broad market prospects, and has become the commanding heights of international competition in the laser field. A number of domestic research units and enterprises are working on power GaN based blue ray semiconductor laser chips.
Welding characteristics of blue laser for non-ferrous fields
Copper laser welding technology is the best reflection of the advantages of blue laser in the welding field. Because the absorption rate of copper to the near-infrared laser is very low, the absorption rate fluctuates greatly, and the copper itself has good thermal conductivity, it is easy to appear poor weld formation, easy deformation, hot cracks, spatter, porosity and other welding defects during laser welding. A breakthrough in laser welding technology of red copper has been achieved by utilizing the high absorption rate of red copper to blue laser. In the welding process, the energy can be quickly converted into heat energy, resulting in the melting of the copper surface and the formation of a molten pool, and then the heat is transferred to the interior of the workpiece through heat conduction, so as to achieve the welding effect without splash and porosity.
The blue laser welding system uses Kaplin blue laser as the light source, equipped with collimated focusing welding head, fiber-blue composite welding head and table, which can realize a variety of continuous and pulse welding methods. The system performs well in lap and butt welding, especially for welding of highly reflective materials such as copper, gold, stainless steel and alloys.
The use of He (or Ar) gas as a protective atmosphere in the welding process verifies the welding process under different flow rates, welding speeds, power and defocus. The blue laser can not only do multi-layer welding of copper foil with a thickness of 20μm, but also achieve 0.3mm, 0.6mm and other different thickness of copper butt welding. During the welding process, the surface of the weld is stable, no splash, and the surface is smooth; Under 40X microscope, no pores were found inside the weld. In addition to laminated copper and butt welding, in the new energy electrode hairpin, electronic chip beryllium bronze pin welding, blue laser has excellent welding performance. Considering that blue light can not achieve deep penetration welding and the light spot is large, we explore the composite application of blue light and red light. Red light can achieve a small core diameter and high power to improve the depth of penetration, while blue light uses the high absorption rate of copper to rapidly melt the material while enhancing the absorption rate of red light. In addition, the large spot of blue light can also expand the molten pool and delay the solidification of the molten pool, thus achieving low spatter, low porosity and high quality welding to a certain extent.
Blue laser also has certain advantages in welding stainless steel. Due to the high absorption rate of blue light in stainless steel, the blue laser can effectively convert energy into heat, quickly melt the stainless steel surface, and achieve high-quality welding. At the same time, the blue laser has a higher energy density and a smaller heat-affected zone, which helps to reduce thermal deformation and oxidation of the welding area, thereby improving the welding quality.
For the welding of aluminum and copper-aluminum composite materials, blue laser also has certain applicability. Aluminum materials have a relatively low absorption rate of blue light, but with the right power density and spot shape, blue laser can also achieve effective welding of aluminum materials. In addition, the combination of blue light and red light laser can be considered as a composite application to improve the welding effect on aluminum materials to overcome the limitation of low blue light absorption of aluminum materials [3]. Considering the material characteristics and laser characteristics, a blue laser scheme suitable for aluminum welding can be designed to meet the needs of different application scenarios.
In addition, blue light also provides a new possibility for copper-aluminum composite welding, due to the high temperature of infrared laser welding, resulting in a large number of brittle intermetallic compounds when copper-aluminum composite, composite application of blue light and red light laser can also play a role in the welding of copper-aluminum composite materials to improve welding quality and efficiency.
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