The Arc Characteristic And Metal Transfer Of Underwater Wet FCAW Under External Longitudinal Magnetic Field

Underwater wet automated welding is an urgent demand underwater weldingtechnology for marine exploitation.this paper proposes a new idea to improve thequality of underwater wet FCAW(WFCAW), which is aim for improving arcstability, metal transfer, and weld structure and mechanical properties ofWFCAW.the magnetic control device are designed according to the underwaterworking environment and the requirements of magnetron, and a experimentalplatform of underwater wet welding has been set up. Through the combination ofnumerical simulation and experiment,researching the arc characteristics,metaltransfer,appearances of weld and cooling properties of WFCAW under externallongitudinal magnetic field,lay a solid foundation for further enhance the quality ofunderwater wet welding and achieve the underwater wet automated welding.First analysis the mechanism of arc under external magenetic filed, the resultsshowed that the distribution of the magnetic field determines the expansion orcontraction of the arc,and the size of the magnetic field determines the degree ofexpansion and contraction, according to the characteristics of underwater arc andsimulation results of the magnetic field, The magnetic head which lower end istapered surface meet the claim.Carry out verification test and the results consistentwith the analysis.Study the arc characteristics of WFCAW under external longitudinalmagenetic field by the combine of electric signal analysis system and high-speedcamera,studies show that underwater arc is burned in the "arc bag",the periodicbroken of "arc bag" directly affect the burning and extinguish of the arc,makingthe short-circuit and extinction process is almost inevitable.The arc voltage andcurrent variable coefficient inverse are set as the evaluation standard of arcstability, researchs show that with the increase of magnetic field intensity, thestability of the arc rise first and then fall.Free transfer modes and short-circuit transfer mode are builded by fluiddynamic theory respectively.carry out the numerical simulation of WFCAW andWFCAW under external longitudinal magenetic field by the way of secondarydevelopment of Ansys-fluent.And short-circuit transfer is analyzed and validatedby the the electrical data indirectly.The results show that the drop transfer ofWFCAW appears difficulties since the reduce of the electromagnetic force and theplasma stream force,and a appropriate magnetic field can improve the frequency of metal transfer and reduce the droplet size,thus promote metal transfer.The appearance of welds and cooling properties of WFCAW under externallongitudinal magenetic field,the results show that the magnetic field can balancethe influence of water,that is making the weld width increase and the weld heightreduce. Establish a numerical model of the heat conduction of underwater wetwelding and carry out numerical simulation,the results show that the longitudinalmagnetic field can make the weld zone temperature distribution more uniform andcooling speed reduce,and that is good for organizational changes of weld metal.