Study On Plasma And Molten Pool Dynamic Behaviors For Low-power Scanning Laser-TIG Hybrid Welding

Compared with laser welding or arc welding,laser-arc hybrid welding technology has the advantages of high energy utilization,large welding penetration,stable welding process and low assembly precision.However,in the conventional laser-TIG hybrid welding process,the laser is fixed relative to the arc,and there are few studies on laser scanning-TIG hybrid welding.In the TIG welding process,the introduction of the laser can stabilize the arc,especially after the arc is stabilized,which can make the laser scanning-TIG hygrid welding process become stable,and at the same time,the better surface forming can be obtained.Based on the three-factor fourlevel orthogonal experiment method,the relative position between the laser and the arc is found when the laser-arc interaction is strongest,that is,the arc length is 1 mm,the heat source spacing is 1.5 mm,and the welding gun inclination angle is 45?.On this basis,the effects of laser defocus and laser power on weld penetration are studied.By analyzing the results of orthogonal experiments and laser power experiments,the following interaction mechanism between laser and arc is obtained: under laser action,the arc will preferentially form a conductive path through the laser plasma.When the heat-source spacing Dla is small,the arc will be significantly compressed,while the welding torch angle ? and the arc length L determine the center position of the arc welding heat source together.When the laser acts on the center of the heat source,the arc pre-heating will greatly increase the laser absorption rate,and the penetration depth will significantly increase.In addition,the shorter the arc length,the higher the arc energy density,which helps further increase the penetration depth;Under optimal position parameters,when the laser-power percentage is 10%–50%,the weld profile shows the characteristics of laser heat conduction welding;when the laser-power percentage is 50%–80%,the weld profile shows the characteristics of laser deep penetration welding;and when the laser-power percentage is 80%–100%,though the laser deep penetration welding is obtained and the arc compression is more obvious,the duration of laser action is too short,so the valid penetration is shallow and accompanied by a large splash.Through the observation of the arc and the molten pool dynamic behavior during the laser scanning-TIG hybrid welding process,it is found that the arc will shift synchronously with the laser scanning motion due to the attraction of laser to arc.So when the laser is in different scanning modes,the arc will also exhibit a corresponding synchronous offset change;When the laser is scanned in a circle,half of the incident position is close to the lower wall of the molten pool as the laser is incident on the molten pool,resulting in a relative decrease in the downward flowing molten metal and a relative increase in the upward flowing molten metal,and then the molten pool flow behavior with a large semicircle and a small semicircle is formed under the effect of the arc force and the surface tension;When the laser is scanned in a straight line,a small portion of incident position is close to the lower wall of the molten pool as the laser is incident on the molten pool,resulting in that the upward flowing molten metal is more than the downward flowing molten metal,and then the molten pool flow behavior with a slightly larger upper semicircle and a slightly smaller lower semicircle is formed under the effect of the arc force and the surface tension;when the laser is pulsed for scanning,the position of the laser incident molten pool is fixed and close to the center line of the molten pool.The upward flowing molten pool metal is nearly equal to the downward flowing molten metal,so the molten pool flow behavior with two approximate semicircles is formed under the effect of the arc force and the surface tension.