Simulation Of Fe-0.4%C Alloy In Welding Pool During Solidification Process

With the rapid development of science and technology,the pursuit of excellent quality,high efficiency and low cost of welding process has become an eternal theme.Due to welding thermal process and microstructure are the key factors that influence and determine the quality and efficiency of welding,also the scientific basis of welding technology,the accurate calculations of welding thermal process and microstructure by using numerical simulation have great significance for welding metallurgy,stress and strain analysis,process control and optimization,etc,and is important way that make the welding technology from qualitative and experience to quantitative and science.Based on the previous research,a solute diffusion controlled model is developed by coupling finite for simulating welding thermal field of Fe-0.4%C alloy during the solidification of welding molten with cellular automata,which is used for simulating the dendrite growth morphology and solute concentration distribution of single and multiple equiaxed dendrite with preferred orientation,columnar crystals,and columnar-to-equiaxed transition.The effects of thermal undercooling,curvature undercooling,and component undercooling is considered in this model.The coupling of macro temperature field and micro dendrite growth reproduced the dendrite growth morphology and solute concentration distribution of Fe-0.4%C binary alloy during the solidification of welding molten pool.At same time,different impacts temperature gradient,cooling rate,amplitude and nucleation substrate columnar-to-equiaxed on grains is invested.The results show as fellow:The isotherm distribution is half ellipse in shape at the beginning of solidification.The temperature decreases from the center of molten pool to the edge.With the increasing of solidification time,the temperature in molten pool decreases overall,and the isotherm distribution is semi-closed half concentric circles.In the process of solidification,the evolution of dendritic growth is that nucleation first appears on the edge of molten pool and forms stable boundary layer,then the columnar crystals grow quickly into supercooled melt on parallel lines.The multi-dendrites with different size and shape that grow along their preferential growth orientations appear in the mid and late of solidification,and the secondary and ternary dendrites of which grow competitively.Finally,the total number of crystal nucleus gradually reaches saturation.As the stack and interaction each other of the solute field formed by the diffusion of dendrites hinder the nearby dendritic growth,the enrichment of solute is serious.The primary dendrite arm space reduces with increasing temperature gradient.The greater growth rate can be obtained under the faster cooling rate,and the better the dendritic growth,the more serious the microsegregation and the shorter the time required for evolutionary process.After exerting disturbance,the dendrite with the secondary and ternary branch is obtained,and the greater the disturbance amplitude,the more complicated the branching morphology of dendritic growth.