The Modeling And Simulation Of The Nozzle For Ultra-narrow Gap TIG Welding

At present, the fine grain and high-quatilly are widely used in the industries, such as pressuer vessel, boiler, machinery, Marine structure and shipbuilding, and pressuer pipe ,the heat affected zone soften of the fine grain steel welding is the main problem facing. Ultr-narrow gap welding is a high efficient welding technology, it can effectively solve the heat affected zone soften of the fine grain steel welding, and obtains the excellent weld structure and mechanical properties. To carry out the welding technology, the key problems which need to be resolved is that, arc can't maintain its stability by adjusting action, and climbes along the lateral wall ,leading to the sidewalls fusion; and air is immixtured into the gas which is spraied into the narrow gap from the welding torch, making the molten pool and tungsten oxidation. On the basis of using flux strip restricting the arc to effectively prevents arc climbing along the lateral wall, accroding to studing the characteristics of the flow pattern and flow field for the ultra-narrow gap TIG welding, the theoretical models of the nozzle for the Ultra-narrow gap welding torch are established, and they were developed by the way of numerical simulation and test evluation. The work was done as follows.(1) The theoretical models of STN and HTN for Ultra-narrow gap TIG welding torch were established. For the technical requirement of the ultra-narrow gap welding, and the theoretical analysis and test results for the ceramic nozzle and flat nozzle ,which were proposed based on the traditional design method, the effect of the gas flow to gas protection was studied. Accroding to the fluid mechanics and the kinetic gas theory, the theoretical models of the welding torch for Ultra-narrow gap TIG welding were put forward.(2) The finite element models of the theoretical were established. By entity modeling and reasonably dividing grid, the flow patten and flow field of the finite element models were simulated. The characteristics of the flow field affected by spacing and the flow of the gas was studied, and the effect of gas protection for them was assessed .(3) The nozzle entities of the finite element models were processed, and the simulation results were evaluated by the actual gas protection test. The two developed nozzles'gas protection was tested by the special copper wire nets , in different gas flow range and space , and compared with the simulation results. The comparative analysis of the test and the numerical simulation results show that, the STN can ensure the technical requirement of gas protection for ultra-narrow gap TIG welding. At the same time, the optimization design method not only can reduce its design cost, but also can make the design cycle shorten.