Study On Welding Joint Of Dissimilar Metals By Coupled Thermo-hydro-mechanical Method

Nowadays,dissimilar material welding has been widely applied to many industries.Because of the difference in material properties,the fluid flow in the molten pool becomes more intense,which has a significant effect on the phase distribution,temperature and stress field.In the study of dissimilar welding,it is necessary to consider the effects of fluid flow in the molten pool.In this paper,a three dimensional transient thermo-hydro-mechanical model is developed and validated.This model is used to study the molten pool behavior,the stress field and welding deformation.The main content and results are following:(1)Based on computational fluid dynamics(CFD)method,the 3D transient model is developed to study the laser welding of low carbon steel and stainless steel couple.The molten pool behavior and the effects of process parameters on it are analyzed.Results show that there is an asymmetric behavior in fluid flow and temperature distribution.The peak of temperature and velocity both occur on the low carbon steel side.With the increasing input power,the peak temperature,velocity,the temperature gradient and the molten pool size increase simultaneously.The reverse phenomenon is observed with the increasing welding speed.(2)The thermo-hydro-mechanical model is developed and validated.Using this model,the similar material welding is taken as a research example to study the stress field and welding deformation.The calculated results are compared with the experimental results and a well agreement is obtained.(3)The effects of fluid flow on molten pool behavior and weld strength are investigated using both with and without fluid flow model.Results show that the fluid flow has a significant effect on the molten pool and this effect gradually weakens with the distance;In the model with considering fluid flow factor,the peak temperature and temperature gradient are both smaller than those in the model without considering fluid flow factor.The effect of fluid flow on residual stress is more obvious on low carbon steel side.In term of transverse shrinkage,the value obtained in the model with fluid flow is bigger than that obtained in the other model on the stainless steel side.The reverse trend appears on the low carbon steel side.The angular distortion in the model with fluid flow is larger than that in the other model.In summary,the calculated results obtained from the model with considering fluid flow are better agreeable with the experimental results.