New development direction of laser welding technology

Plastic laser weldingThe technology is a comprehensive technology that integrates laser technology, welding technology, automation technology, material technology, mechanical manufacturing technology and product design, and is ultimately embodied in special equipment and technology. As an important part of advanced manufacturing technology, laser welding technology has broad application prospects in the future aviation manufacturing industry. The development direction of laser welding technology mainly includes the following aspects

1. Filler wireLaser Welding

Laser welding machine Laser welding generally does not use filler wire, but has high requirements for the assembly gap of welds, which is sometimes difficult to guarantee in actual production, limiting its scope of application. The use of filled laser welding can greatly reduce the requirements for assembly gaps. For example, for an aluminum alloy plate with a thickness of 2mm, if filler wire is not used, the gap between the plates must be zero for good forming. For example, using a 蠁1.6mm welding wire as the filler metal, even if the gap is increased to 1.0mm, it can ensure good welding formation. In addition, the filler wire can adjust the chemical composition for multi-layer welding of thick plates.

2. Beam Rotation Laser Welding

The method of rotating the laser beam for welding can also greatly reduce the requirements for weldment assembly and beam alignment. For example, when butt-jointing 2 mm thick high-strength alloy steel plates, the allowable joint assembly gap is increased from 0.14 mm to 0.25 mm; for 4 mm thick plates, it is increased from 0.23 mm to 0.30 mm. The alignment allowable error of the beam center and the weld center is increased from 0.25 mm to 0.5 mm.

3.Online detection and control of laser welding quality

The use of plasma light, sound and charge signals to detect laser welding process has become a hot topic of research at home and abroad in recent years, and a few research results have reached the level of closed-loop control. The sensors used in the 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 and ultraviolet signals of plasma.

2) Plasma Charge Sensor (PCS): Use the nozzle as a probe to detect the potential difference between the nozzle and the workpiece of plasma charged particles (positive ions, electrons).

2. System Function.

1. Method for identifying laser welding process. Stable deep melting welding process has plasma, and PS and PCS signals are strong

Stable thermal conductive welding process, no plasma is generated, and PS and PCS signals are almost zero

In the plasma stable welding process, plasma is intermittently generated and disappeared, and PS and PCS signals rise and fall intermittently.

2. Diagnose whether the laser power delivered to the welding area is normal. When other parameters are constant, the intensity of PS and PCS signals is related to the power entering the welding area. By monitoring the PS and PCS signals, we can understand whether the light guide system is normal and whether the power in the welding area fluctuates.

3. Automatic tracking of nozzle height. The PCS signal decreases as the nozzle-workpiece distance increases. Using this rule for closed-loop control can ensure that the nozzle-workpiece distance remains unchanged and realize automatic height tracking.

4. Automatic optimization and closed-loop control of the focal position. Within the deep melting welding range, when the focal position of the light beam fluctuates, the plasma light signal received by the PS will also change, and the PS signal is *less than* the optimal focal position (the keyhole is the deepest at this time). According to the discovered rules, automatic optimization and closed-loop control of the focal position can be achieved, so that the focal position fluctuation is less than 0.2 mm and the melting depth fluctuation is less than 0.05 mm.