Computational Analysis of the Effects of Process Parameters on Molten Pool Transport in Cu-Ni Dissimilar Laser Weld Pool

Abstract

A three-dimensional, transient numerical model is used for analyzing the effects of process parameters such as laser power and the laser scanning speed on turbulent momentum, heat and mass transport in a typical dissimilar metal weld pool of a copper-nickel binary couple. The conservation equations are solved in a coupled manner using a semi-implicit pressure linked algorithm in the framework of a finite-volume approach. Turbulence effects are taken care of by employing a suitably modified k–ϵ model, which accounts for solid–liquid phase change in a turbulent environment. The solid–liquid phase change aspects are addressed using a modified enthalpy-porosity technique. Subsequently, the developed turbulent transport model is used to simulate continuous welding of a copper-nickel binary couple in a butt joint configuration for different values of the laser power and laser scanning speed, in order to assess their influences on the pool geometry, cooling rate, and heat, momentum and species transport inside the molten pool. In order to investigate the effects of turbulence, the results of the turbulent transport simulations are compared with the results obtained from the simulations without turbulent transport for the same values of process parameters. Significant differences are observed on comparing the results obtained based on simulations with and without turbulent transport, which provide valuable insights for controlling the process parameters based on manufacturing needs. It has been observed, in general, that the enhanced diffusive mixing in turbulent transport leads to lower maximum values of mean velocity, temperature, and cooling rate than those obtained from the corresponding simulations without turbulent transport.

The authors are grateful to Dr. G. Phanikumar for many useful discussions.

Notes

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*Based on private communication with Prof. H. K. Bhadeshia, Cambridge University.

For cases, the absorptivity of laser beam η and the radius of top heat flux distribution r _q are taken to be η = 0.11 and r _q  = 0.5 mm respectively.