Laser welding machine welding technology is a combination of laser technology, welding technology, automation technology, material technology, mechanical manufacturing technology and product design as one of the integrated technology, and ultimately embodied as a complete set of special equipment, but also as a supporting process. As an important part of advanced manufacturing technology, laser welding technology has a broad application prospect in the future aviation manufacturing industry. The development direction of laser welding technology is mainly in the following aspects
1. laser welding of filler wire
Laser welding machine generally does not fill the welding wire, but the welding parts assembly gap requirements are very high, sometimes it is difficult to ensure in actual production, limiting its application. Laser welding with filler wire can greatly reduce the requirement for assembly clearance. For example, aluminum alloy sheet with a thickness of 2 mm, if no filler wire is used, the gap between the sheet metal must be zero in order to obtain good forming. For example, if the welding wire with a thickness of 1.6 mm is used as filler metal, even if the gap is increased to 1.0 mm, the weld seam can be well formed. In addition, filler wire can also adjust chemical composition or carry out thick plate multilayer welding.
2. beam rotating laser welding
The method of rotating laser beam for welding can also greatly reduce the requirements of welding assembly and beam alignment. For example, when 2 mm thick high strength alloy steel plate is butted, the allowable butt gap increases from 0.14 mm to 0.25 mm, while for 4 mm thick plate, the allowable butt gap increases from 0.23 mm to 0.30 mm. The alignment error of the beam center to the weld center is increased from 0.25mm to 0.5mm.
3. on line inspection and control of laser welding quality
In recent years, the detection of laser welding process by using the signal of light, sound and charge of plasma has become a hot research topic at home and abroad. A few research results have reached the level of closed-loop control. The sensors used in laser welding quality detection and control system and their functions are briefly introduced as follows:
(1) plasma monitoring sensor
1) Plasma Optical Sensor (PS): Its function is to collect the characteristic light-ultraviolet signal of plasma.
2) Plasma Charge Sensor (PCS): The nozzle is used as a probe to detect the potential difference between the nozzle and the workpiece due to the inhomogeneous diffusion of plasma charged particles (positive ions, electrons).
(2) system functions
1) identify which way the laser welding process is. In stable deep penetration welding process, there are plasma, PS and PCS signals are very strong; in stable thermal conduction welding process, there is no plasma, PS and PCS signals are almost equal to zero; in unstable mode welding process, plasma is produced and disappeared intermittently, and corresponding PS and PCS signals rise and fall intermittently.
2) Whether the laser power transmitted to the welding area is normal or not, and when other parameters are fixed, the intensity of PS and PCS signals corresponds to the power incident to the welding area. Therefore, monitoring the PS and PCS signals can be known whether the light guide system is normal, whether the power of the welding area has fluctuations.
3) automatic tracking of nozzle height. The PCS signal decreases as the distance between nozzle and workpiece increases. The closed-loop control based on this law can keep the distance between the nozzle and the workpiece unchanged and realize the automatic tracking of the height direction.
4) focus position automatic optimization and closed loop control. In the range of deep penetration welding, when the beam focus position fluctuates, the plasma optical signal received by PS changes accordingly, and the PS signal is the smallest at the best focus position (at this time the hole is the deepest). According to this rule, the focus position can be automatically optimized and closed-loop controlled, so that the focus position fluctuation is less than 0.2 mm and the penetration depth fluctuation is less than 0.05 mm.
Summary:
While laser welding technology is widely used, it is also continuously studied in depth. In view of its shortcomings, the heating performance of other heat sources is used to improve the laser heating of workpiece. On the basis of maintaining the advantages of laser heating, laser welding with other heat sources is carried out. There are laser and arc, laser and plasma arc, laser and induction heat source hybrid welding and double laser beam welding. Composite welding can increase welding penetration, improve joint performance, reduce equipment costs, and improve welding speed and productivity. In short, laser welding has high production efficiency, stable and reliable processing quality, good economic and social benefits. In an era of endless and renewal of new equipment, new materials, new technologies and new processes, producers should not only understand the characteristics, advantages and requirements of laser welding, but also recognize the many innovations and future trends in this field. Only in this way can they grasp the trend of technological popularity and keep up with the times.