Scaling molten pool shape induced by thermocapillary force in melting

• Main Authors: Chao-lung Lin, 林超隆
• Other Authors: Peng-Sheng Wei
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/b3ubf9

碩士 === 國立中山大學 === 機械與機電工程學系研究所 === 97 === The molten pool shape and thermocapillary convection in melting or welding of metals or alloys having negative surface tension coefficients and Prandtl number greater than unity are determined from a scale analysis. Negative surface tension coefficient indicates that the surface flow is in outward direction, while Prandtl number greater than unity represents that boundary layer thickness of conduction is less than that of momentum. Determination of the molten pool shape is crucial due to its close relationship with the strength, microstructure and properties of the fusion zone. Since Marangoni and Reynolds number are usually greater than ten thousands, transport processes can be determined by scale analysis. In this work, the molten pool is divided into the hot, intermediate and cold corner regions on the flat free surface, boundary layers on the solid-liquid interface and ahead of the melting front for analysis. The results find that the pool shape, surface speed and temperature profiles can be self-consistently evaluated as functions of Marangoni, Prandtl, Peclet, Stefan, and beam power numbers. The predictions agree with numerical computations and experimental data in the literature.