Development Of Wire Cutting With Drug Core In Underwater Wet Arc Cutting And Study On Cutting Thick Plate

As an important branch of ocean construction technology,underwater cutting technology plays an important role in removing abandoned offshore platforms and repairing offshore pipelines.Underwater wet arc cutting is an underwater cutting method with simple equipment,reliable technology and low cost.However,there are few studies on this technology in China,especially on high strength thick plates.The research and development of underwater wet arc cutting thick plate has an important role in promoting the progress of underwater construction technology in China.Three different components of flux-cored wire have been designed and made to find out the best one for underwater cutting.On this basis,the mechanism of underwater cutting 25 mm thick plate and the influence of active coating on cutting are explored by using underwater high-speed video camera and electric signal acquisition technology.Then,according to the actual needs of engineering,the study of 32 mm thick plate cutting has been carried out,the influence of process parameters on cutting shape and arc stability was obtained.The results show that the peak temperature of exothermic wire is the highest,while that of oxidized wire is the lowest;the peak temperature drop rate of oxidized wire is the slowest,the average temperature is the highest,and the peak temperature drop rate of gas-forming wire is the fastest and the average temperature is the lowest.Among the three kinds of wire,oxidized wire has the best thermal performance,which is beneficial to underwater wet arc cutting.The process of underwater wet arc cutting thick plate has periodicity,which is a continuous ‘perforation' process.The arc has good stability in low position combustion and poor stability in side position and low position co-combustion.The cutting efficiency and arc stability of underwater wet cutting are improved by underwater active coating.Compared with uncoated workpiece,the arc extinguishing time and number of arc extinguishing times of coated workpiece are greatly reduced.Different technological parameters have important influence on shape of cut cavity and arc stability.Wire feeding speed mainly affects the position of arc combustion,the higher wire feeding speed,the lower arc burning position;cutting voltage has a greater impact on the width of the cut,the larger cutting voltage,the wider the kerf;cutting speed has an impact on the formation of the cut mainly reflected in the aspects of bridging and slag hanging,the faster the cutting speed,the more serious the bridging and slag hanging.The increase of cutting voltage and cutting speed improves the stability of arc in varying degrees,while the increase of wire feeding speed reduces the stability of arc.When wire feeding speed is 5.4m/min,cutting voltage is 48 V and cutting speed is 90 mm/min,cutting 32 mm thickness Q345 steel plate by this method in shallow water can achieve better results and higher arc stability.