Overall Deformation And Welding Path Selection Research Of Large Vessel Nozzle With High Power Laser

The development of ship industry plays an important role to both national economy and national military strength. The nozzle is one of the most important parts which affects the power performance of a ship, so the national level puts a lot of research on the welding technology and profile/performance controlling. The nozzle is a steel structure installed around the propeller. The structures and sizes are different according to different types of ship, one of the common structures is multi-surface combination. The main role of the nozzles to improve the efficiency of ship propulsion, and its main processing technology is welding. Because of its special structure and function, the requirements of welding process are relatively high.Welding is a relatively complex but widely used processing technology. For large thick walled vessel nozzles, the traditional arc welding is unable to meet the higher demands for shipbuilding. To develop a new method for large nozzle welding, this paper has conducted some research on path selection of welding head and the global deformation of nozzle by adopting a 4kW power laser as the welding heat source.At first, the subject background is introduced. And the development trend of welding technology at home and abroad are analyzed. The focus of discussion is laser welding technology.Secondly, structure of the nozzles described in detail and requirements of the welding process are analyzed. According to the requirements, the typical welding head is made as T type. According to the thermo-elastic theory and inherent strain theory, a method combining the two theories with the width of heat affected zone by utilizing ANSYS software package is established.Then, a numerical simulation of the temperature filed distribution and deformation of T type welding work piece in three different welding paths are carried out. After comparing and analyzing the computation results of deformation in three different welding paths, the optimized welding plan can be obtained. The specific results is that multi stage symmetric welding method which makes least distortions the best welding path.Finally, the global deformation is analyzed using the optimized welding path. The section extension method is employed to calculate the deformation size. And the result turns to 0.258 mm. Take the superposed deformation into account, the global deformation will not exceed 5.16 mm, which is smaller than that of the traditional arc welding process.