| In modern manufacturing production,as a kind of important welding method,pulsed gas metal arc welding(P-MIG)has the advantages of low heat input,good weld quality,and suitable for all position welding.The droplet transfer process,especially the droplet velocity,has a significant influence on welding quality,and thus has important research value.At present,most researches were focus on detachment and impingement stage,while the droplet transfer process in arc plasma has been much less mentioned.It is necessary to study deeply onto this issue.Based on digital image processing technology,the edge of the droplet was extracted,and the transition process of the droplet at different process parameters were analyzed.In this study,the pulsed gas metal arc welding system was established,including welding system,high speed camera system and multi-information synchronizing acquisition system.The system can effectively overcome the influence of arc and the droplet images were clear.According to the characteristics of the original images,a series of image processing operations were carried out to extract the edge of droplet,and the droplet mass center was obtained.A new method was developed to calculate the droplet velocity according to the result of digital image processing,then the droplet velocity transfer curve was obtained.In this study,the droplet transition process in medium arc length was analyzed,and the droplet transition was divided into three parts: arc column region,near anode region and near cathode region.The droplet did uniformly accelerated motion in arc column region while larger deceleration in near cathode region and slight deceleration in near anode region.The force situation of droplet transferred in three parts were analyzed in quantitatively and qualitatively.The droplet transition process at different wire feed rate were also analyzed.The arc length is longer and the next pulse was coming while the droplet hasn’t impinged into weld pool when the wire feed rate is slow.The arc length is shorter and the droplet tended to slow down in whole arc space when the wire feed rate is fast.The droplet transition process were analyzed at different welding speed.The welding speed is mainly affects the heat input of the weld pool,and affects the droplet transition state in near cathode region.At last,the droplet transition process were analyzed at different shield gas flow.The analysis of the welding process can providing a basis for the study of the mechanism of the welding process,and it is better for dynamic control of the welding process. |
