Study On The Vapor Plume Suppression And Weld Forming Control During Deep Penetration Laser Welding Of Thick Plate With Fiber Laser

As the technology of laser maser develops,full-penetration laser welding of thick plates is widely used in spaceflight,shipbuilding,vehicle and energy.Compared with traditional and common laser welding,high-power laser welding of thick plates is easy to generate many factors disturbing welding process such as vapor plume,big splash,and defects like root sagging and top subsidence.The requirement of welding stability and weld quality are demanding in major engineering projects,for example,aerospace and energy industries.It is necessary to study deeply and systematically to guarantee the stable welding process and high quality of weld.In this paper,the method to restrain the vapor plume and the control technology of weld forming process is studied to solve the defects above.The detailed works are as follows:(1)A multi-functional air blowing protection device is designed and developed in high power laser welding of thick plates.ANSYS software is used to analyze the air flow of the device and the differences between the four combinations of blowing gas in vapor plume suppression and weld forming control are compared and analyzed.The results show that the steam plume can be effectively suppressed and the surrounding area of the molten pool can be isolated by the proper configuration of horizontal,side and drag hood.(2)The high speed camera is used to observe the vapor plume behavior in the keyhole and outside the keyhole.Variation characteristics under different parameters is also studied.The results show that the keyhole certain angle and is fluctuant.Positive and negative focus can increase the diameter of the keyhole and decrease the effect of vapor plume.The injection-height of metal vapor is high and periodicity,while the plasma height is small and stable.The amount of metal vapor is obviously greater than that of plasma in fiber laser welding,which plays a major role in laser attenuation.(3)Full-penetration laser welding of 15 mm 304 stainless steel is made with the laser power of 16-kW.The forming characteristics of weld under different welding attitude and welding parameters are compared.The results demonstrate that serious collapse can be avoided by horizontal welding,the amount of splash in quick welding with small defocus is obviously greater than that in slow welding with large defocus,the formation of surface hump is related to the periodic change of vapor plume outside the hole and the formation of weld hump can be effectively controlled by vapor plume suppression.(4)The multi-functional protection device was successfully applied to the coil box welding.The quality of the weld and welding stability meet the welding requirements.