| The laser penetration welding is popularly used in industry field. The use of high-power density laser beam to weld many alloys often leads to appreciable changes in the composition and properties of the weld metal. In this paper, a model is presented to predict the weld metal composition change during laser penetration welding. And some research has been carried out to study the weld microstructure transform. The temperature field is simulated from a well-tested three-dimensional transient heat transfer and fluid flow model through the numerical solution of the equation of conservation mass, momentum, and energy. The influence of plasma and keyhole is considered. Three aspects are considered in simulating the composition changes. The first, vaporization due to pressure gradient, It's the most important factor; The second, vaporization due to concentration gradient; the third, the attraction between the positively charged metal ions and the negatively charged vaporizing surface leads to enhanced condensation of metallic species because of the exist of the plasma. Composition changes in weld are founded because three factors are existed at the same time. The model is verified also in this paper, the results of the experiment are in good agreement with the calculation; the error is founded because of the complicated theory of the laser penetration and some simplicities of the model. The weld microstructure transform is also analyzed in this paper; the results of the theory are in good agreement with the results of the experiment. |
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