大熔深K-PAW熔池及电弧视觉行为特征分析研究OACSTPCD

With the unique advantages,keyhole plasma arc welding(K-PAW)is widely used in the welding and manufactur-ing of medium-thick plates,and is gradually developing for larger thicknesses welding.However,the increase of thickness is also accompanied by the problem of keyhole instability,which restricts its application in practical production.In order to provide theoretical basis for the design of stable piercing process,the characteristic size variation of K-PAW weld pool of 14 mm thick 304 stainless steel under the control strategy of"controlled constant piercing"and the weld pool behavior were analyzed.Through visual detection and electrical signal synchronous acquisition system,the morphology characteristics of molten pool in the process of large-penetration K-PAW were quantitatively analyzed,and the changes of molten pool charac-teristic parameters under controlled pulse conditions were explored,as well as the synchronous dynamic behavior rules of molten pool characteristics and electrical signals.In the blind hole stage of the first 14 seconds of plasma arc initiation,the weld pool is unstable with the accumulation of arc heat,and the size oscillates,with the maximum oscillation amplitude ex-ceeding 10 mm.At the same time,the aspect ratio of the weld pool also changes in the range of 1.0～1.6.With the perforation occurring at the 15th second,the molten pool reached equilibrium,and the aspect ratio reached its peak at 19 s.The molten pool remained stable and its shape did not change greatly in the sustaining stage.In summary,the welding stage can be dis-tinguished by the changing trend of the shape of the molten pool.Then,the authors compared the blind hole stage of differ-ent welding currents(280 A,275 A,270 A),and found that the use of larger initial current is conducive to shortening the blind hole time,from 22.9 s at 270 A to 19.8 s at 280 A,and reduce the possibility of welding holes.Finally,the authors found that the distance between the arc center and the front edge of the molten pool can reflect the perforation state.This study verifies the feasibility of the"controlled constant piercing"control strategy,and verifies the feasibility of distinguish-ing the welding stage and piercing by visual features.