Study On Morphology Characteristics Of Laser Deep Penetration Weld Based On Plasma Electrical Signal Detection

In recent years,owing to the unique advantage laser welding has gradually replaced traditional welding processes and it is widely used in various fields such as automobiles,airplanes,ships,and electronics.Due to the extremely high requirements of laser welding for welding parameters and workpiece assembly accuracy,subtle errors can lead to serious welding defects.Therefore,with the widespread popularity of laser welding technology in various industries,the quality monitoring of its processing is particularly significant.Especially in the field of medium-thickness plate welding,the weld depth and weld profile monitoring of laser deep-penetration welding have an important research significance.Aiming at the monitoring morphology of weld profile in laser deep penetration welding,in this paper,a plasma photoelectric signal synchronous detection test system is built,and the test parameters of different heat input conditions are designed.The relationship between the keyhole oscillation and the keyhole depth is analyzed based on the internal pressure balance condition of the keyhole.Based on the coupling between keyhole behavior and plasma behavior and the consistency of plasma oscillation characteristics and plasma electrical signal fluctuation characteristics,the Hilbert-Huang transform analysis method was used to analyze the relationship between the oscillation frequency of the plasma electrical signal and the weld depth during the bead-on-plate welding and butt-welding process of A304 stainless steel.It is found that the oscillation frequency of the plasma electrical signal decreases with the increase of the weld depth,and the relationship between the oscillation frequency of the plasma electrical signal and the weld depth is different under different welding materials and joint forms.In addition,aiming at the problem of weld offset during laser butt welding,in this paper,combined with high-speed camera technology,a plasma two-channel electrical signal detection test system was built.The butt-welding test of A304 stainless steel was carried out under different laser focus offset and workpiece offset conditions.The effects of laser focus offset and workpiece offset on weld morphology,inclination angle of the plasma and plasma two-way electrical signal were analyzed.It is found that the inclination angle of the plasma has a certain correlation with the difference of the plasma two-way electrical signal,and the inclination angle of the plasma can reflect the weld offset.