Research On Laser Welding Characteristics Of TA15 With Locking Joint Type

The locking joint is used in the field of aerospace because it is easy to assemble and seal.The structure has assembly gap and belongs to non penetration welding,so it is easy to produce defects such as collapse and porosity in the process of laser welding.Changing the welding process parameters,such as defocusing amount,welding speed,or using swing laser to weld the lock joint structure,can inhibit the porosity defects,improve the weld forming,so as to obtain high-quality weld.Therefore,in this paper,the influence of conventional laser welding parameters and swing on keyhole stability and weld pool flow is studied.The keyhole defects of keyhole joint are restrained and high quality keyhole joint is obtained by using the influence of process parameters and swing on keyhole stability and weld pool flow.In laser welding of titanium alloy The locking joint,increasing swing can improve the slump defect,make the weld surface smooth and eliminate obvious bulge and depression.The swing frequency and swing amplitude mainly affect the stirring effect of the swing laser on the welding pool,improve the weld formation,and make the height and structure of the weld more uniform.In the case of swing,there is no fish scale on the weld surface of the unfinished bottom lock,but a clear trace of the laser swing path,the weld reinforcement is very small,the surface is flat,and the two ends of the weld are changed from ellipse to rectangle with obvious corner.Based on the numerical analysis method of flow 3D software,the inhibition effect of defocusing amount,welding speed,swing frequency and swing amplitude on welding porosity and the reason of porosity sensitivity of lock joint were analyzed.Increasing defocusing amount can enlarge keyhole opening and improve keyhole stability;Increasing the welding speed can change the eddy current direction of the welding pool flow field and promote the gas escape from the pool;Swing can make the temperature distribution more uniform,promote the material exchange in the depth direction of the molten pool,and help the internal gas move to the surface of the molten pool.The porosity sensitivity of lock joint is due to the collapse of molten metal to fill the assembly gap.In the process,the gas in the transverse assembly gap can not be completely squeezed out,and the gas is drawn into the molten pool,which increases the amount of gas in the molten pool.Increasing defocusing amount,welding speed,swing frequency and swing amplitude can make the distribution of weld material more uniform.The effect of defocusing amount and welding speed on molten pool flow is similar,which is lower than that of swing on molten pool flow.The increase of defocusing amount and welding speed can inhibit the welding porosity,but it will affect the surface forming and slump state of the weld,so the inhibition effect on the welding porosity is limited.When the welding frequency exceeds 80 Hz or the swing frequency exceeds 1.2 mm,the welding porosity is almost completely suppressed.