Mechanism Of Metal Transfer Control In Underwater Wet Flux-Cored Arc Welding Based On Pulsed Current

As the continuous development of the marine industry,China's demand for underwater welding technology is increasing.Underwater welding technology is one of the indispensable technologies in modern marine engineering such as offshore oil platform construction,submarine pipeline installation and maintenance,construction and maintenance of sea-crossing bridges and nuclear power plant maintenance.The underwater wet welding technology based on self-shielded flux cored wire does not require special drainage equipment.It has many advantages such as convenient operation,high efficiency,low cost and so on.It adapts to the trend of intelligent development of welding production automation and is more and more people pay attention to it.In this paper,by detecting the arc bubble and droplet image of the flux-cored wire underwater wet welding process,by comparing the relationship between droplet transfer and bubble behavior and electrical parameters,the research of pulse current on droplet transfer control technology is carried out,and the pulse current is analyzed.For the influence of bubble and droplet transfer behavior,the waveform is designed to realize the pulse current to droplet transfer and bubble regulation.By increasing the droplet transition frequency,reducing the droplet diameter,effectively improving the stability of the welding process,and obtaining good weld formation..The underwater wet welding droplet transfer image capture method is used and optimized,and a clear picture containing droplets,bubbles,arcs and other information is obtained.The visual signal and electrical signal synchronization analysis and processing system are used for data analysis.The factors affecting the transition behavior of droplets during underwater wet welding are summarized.The force of molten droplets under complex welding conditions is preliminarily analyzed.The controllability analysis of these factors and the conditions of the droplet force is verified,and the feasibility of the pulse current control of the droplet transfer regulation during the underwater wet-process flux-cored welding process is verified.By analyzing the collected data,it is found that under the pulse current condition,due to the melting of the welding wire,the drifting rotation of the arc and the special underwater environment,the factors affecting the force and transition behavior of the droplet are reflected in various aspects,including melting.The behavior of the droplet itself and its own gravity,the change in gas production due to the melting speed of the wire,and the magnitude and direction of the arc force due to the uncertain behavior of the arc.By summarizing these factors and controlling the controllability,it is found that the change of the droplet transition behavior during the underwater wet welding process is generated by the interaction of the pulse current change and the bubble behavior change,with the pulse current.The change in the droplet's force balance changes and the behavior of the droplet is released when the current rises and remains for a certain period of time.The influence of the value of the pulse current rise and fall on the droplet behavior is summarized.When the average welding current is 180A and the welding voltage is 27V,the current rise and fall value is 60A,the droplet transition period is 152ms,and the droplet diameter is 2.67mm,-which is about 1.6 times the diameter of the wire(1.6mm).The influence of pulse current on the bubble growth rule is summarized.The effect of bubble on the droplet transfer and the time required for the droplet to grow to a certain size under certain conditions are used.Based on this,the pulse waveform is optimized and tested.The electrical signal and the visual signal found that the droplet transfer frequency was increased from 4.4 Hz to 7.52 Hz.and the droplet diameter was reduced from about 7.2 mm to 2.45 mm(1.5 times the diameter of the wire).