Development trend of the hottest laser welding

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Laser welding development trend

1. Composite welding (YAG laser and pulse MIG composite welding, nd:yag and excimer laser superposition)

while laser welding technology is widely used, people continue to conduct in-depth research on it, and find that it has certain shortcomings: in the process of laser welding, the base metal is heated and melted, vaporized, forming deep melting holes, and the holes are filled with metal vapor, Metal gas interacts with laser to form plasma cloud. Plasma cloud absorbs and reflects laser, reduces the absorption rate of metal materials to laser, and reduces the energy utilization rate of laser; It has high requirements for the end interface of the welded base metal, which is easy to produce dislocation; Easy to produce porosity and cracks; After welding, there are depressions at the interface between the end faces of the base metal, unstable welding process, etc. in order to eliminate or reduce the defects of single heat source laser welding, people use the heating characteristics of other heat sources to improve the heating of the workpiece by laser on the basis of maintaining the advantages of laser heating, so as to weld the laser with other heat sources. There are mainly laser and arc, laser and plasma arc, laser and induction heat source hybrid welding and double laser beam welding. Laser and arc welding are combined. This composite process combines the advantages of laser and arc, that is, the high energy density of laser and the large heating zone of arc. Its advantages:

1) it can increase the welding penetration

2) it can improve the welding speed and productivity

3) it can improve the joint performance

4) it can reduce the equipment cost at the same time, through the interaction between laser and arc, To improve the coupling characteristics of laser energy and the stability of arc, so as to obtain a comprehensive effect. However, the introduction of arc increases the heat input of welding, which will inevitably increase the welding heat affected zone and thermal deformation

2. Control of laser welding (weld pool size, plasma effect, etc.), laser welding model

in the research of penetration control in laser welding process, establishing the relationship between weld pool shape parameters and welding process is the key problem. In the experimental process, the richer the information of weld pool shape is, the better the effect of penetration control in welding process is. According to the keyhole mechanism in laser deep penetration welding, many scholars have calculated the temperature field, liquid flow and keyhole shape and size of laser welding and achieved certain results. For example, Dowden et al. Proposed the inverse bremsstrahlung absorption model of incident laser, assuming that the energy is transferred to the keyhole wall through the conduction mechanism, and a maximum theoretical penetration is obtained by solving the heat conduction equation, Sonti et al. Used the two-dimensional finite element nonlinear model to calculate the three-dimensional transmission process of laser deep penetration welding of aluminum alloy, obtained the three-dimensional temperature field of laser welding, downden analyzed the energy and pressure balance in the small hole, and established a general model of liquid and vapor flow in the small hole. Wang haixing et al. Tested, improved and popularized the method proposed by predecessors to calculate the size of molten pool in the process of laser deep penetration welding, Starting from the energy balance in the process of laser welding, the size of the molten pool under different welding conditions is predicted. Liu Shunhong has carried out the analysis and numerical simulation of the temperature field of thin plate laser welding. The weighted residual method is used in the space domain, and the finite difference method is used in the time domain to discretize the total required structure of force adjustment. The effects of automatic identification of material thermophysical parameters, temperature correlation, melting latent heat and convective radiation on the temperature field are considered, The finite element equation is established and the corresponding program is compiled. With the improvement of image sensing method, people can obtain more characteristic information of weld pool shape from weld pool image, such as weld pool width, length and area. Using this information to establish the relationship with laser welding process parameters will play an important role in weld quality control of laser welding, which will be an important direction of laser welding research

3. Laser generator of laser welding and its process development trend

at present, the lasers used in laser welding are mainly high-power CO2 lasers and pulsed nd:yag lasers. The development of lasers is still focused on the development of laser equipment, such as improving the stability and life of power supply. Up to now, CO2 gas lasers should solve the discharge stability of high-power lasers with the strong support of the state, For YAG solid-state lasers, it is necessary to develop optical pump excitation light source with large capacity and long service life. With direct diode array laser output wavelength, the average laser power in the near-infrared region has reached LKW, and the photoelectric conversion efficiency is close to 50%. These laser equipment and technologies will play a greater role in welding applications. In the research of laser processing and beam quality and processing peripheral devices, we should study the quality requirements of various laser processing processes for laser beams, laser beam and processing quality monitoring technology, optical system and processing head design and development, carry out research on welding process and materials, equipment requirements of welding process and welding process parameter monitoring and control technology, so as to master the welding process of ordinary steel, non-ferrous metals and special steel. (end)

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