Numerical Simulation on the Effect of Gas Pressure on the Formation of Local Dry Underwater Welds

Abstract

The obvious feature of local dry underwater welding is the local drainage of the welding area. The choice of drainage method is one of the important factors affecting the quality of underwater welds. Based on hydrodynamics and thermodynamics, the internal gas flow characteristics and arc combustion of the micro-drainage cover with dual-gas curtains is used to simulate which could not be directly observed in the micro-drainage cover with FLUENT, and then the influence of micro-drainage cover on the weld formation of local dry underwater welding is studied. The simulation results show that under the action of intake mode and channel structure, the drainage gas forms a spiral gas wall with a certain "stiffness" around the arc combustion area, which can both protect the stability of the internal dry environment, and cut down the interference of the low drainage pressure on the flow of the shielding gas. However, the low drainage pressure can not effectively achieve the internal drainage. That is, when the pressure of drainage gas exceeds 0.3 MPa, due to the Bernoulli effect, the turbulence situation is intensified owing to the influence of shielding gas, and the arc column fluctuates greatly, which is consistent with the results of underwater weld formation, and provide theoretical basis and basic data for further study of local dry underwater welding.

Function of Solidification Pressure on the Rising and Breakup of Nitrogen Bubbles in Molten Steel

“…14) Xu found the magnitude of surface tension has a strong influence on the rising of bubbles in the liquid phase. 15) For high nitrogen steel, pressurized metallurgy is recognized as one of the most effective methods for manufacture, including pressurized induction melting, pressurized electroslag remelting (PESR), et al [16][17][18][19] Pressure is a critical metallurgical parameter that has been shown to considerably enhance nitrogen solubility and impede the formation of nitrogen pores. 1,[20][21][22] Despite the extensive research on the formation process of nitrogen bubbles in high nitrogen steel ingots, the impact of solidification pressure on the rising and breakup of nitrogen bubbles in high nitrogen molten steel is still not well comprehended.…”