Study On Solidification Process Of Welding Pool Under Rapid Cooling Condition Based On Lattice Boltzmann Method

The microstructure of the weld has an important influence on the performance of the welded joint.The solidification process of the welding pool can directly affect the microstructure of the weld.The method of adding a physical field can directly affect the solidification process of the welding pool and affect the microstructure of the weld.However,due to the complexity of the welding process,it is difficult to conduct a detailed study on the solidification process of the welding pool by experimental methods.Thanks to the rapid development of computer technology,it has become a trend to simulate the welding process using numerical simulation methods.Therefore,the numerical simulation method is used to study the solidification process of the welding pool under rapid cooling conditions.This paper establishes a Lattice Boltzmann Method(LBM)model for simulating the evolution process of welding pool,based on the basic principle of Lattice Boltzmann Method.The LBM model was effectively coupled with cellular automata(CA)method for the simulated welding pool microstructure nucleation and growth to construct the CA-LBM model.Firstly,the accuracy of the established two-dimensional numerical analysis model is verified by checking the classical examples and the actual welding test methods.Then,the CA-LBM coupling model was used to simulate the solidification process of the welding pool under different rapid cooling parameters.Finally,the effects of different rapid cooling conditions on the solidification process of the weld pool were analyzed.Research indicates:Firstly,the influence mechanism of rapid cooling conditions on the solidification process of the welding pool is that the local cooling effect of the cold source causes an increase in the temperature gradient and the concentration gradient in the welding pool,and the surface tension gradient is positively correlated with the temperature gradient and the concentration gradient.Therefore,the Marangoni convection caused by the surface tension gradient is more intense,and the Marangoni convection exerts a stronger agitation effect on the welding pool.This strong agitation of the welding pool reduces the unevenness of the concentration field in the weld structure,and at the same time,the nucleation rate increases due to the increase in the degree of subcooling of the welding pool,and finally the solidification structure of the weld is combined under the combined action.It has been refined.Then,the influence of rapid cooling conditions on the solidification process of the welding pool is positively correlated with the magnitude of the rapid cooling power.Under the condition of rapid cooling power,reducing the area of the cold source can improve its influence on the solidification process of the welding pool.The mechanism of action is to increase the rapid cooling power per unit area,increase the temperature gradient and concentration gradient in the welding pool,and thus increase the surface tension gradient of the welding pool,which makes the Marangoni convection effect more obvious.Finally,when the cold source has the same rapid cooling process parameters,its action position will also have an effect on the rapid cooling effect.In the simulation calculation results of this paper,the cold source acts on the back side of the base material and has basically the same cooling.The effect is that they have the same effect on the solidification process of the welding pool;when the cold source acts on the same side of the base material as the heat source,the cooling effect is not obvious,and the influence on the solidification process of the welding pool is small.