New Method and Device to Fast Measure Surface Tension of the Melt and Its Applications in Foundry
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SURFACE tension is one of the important physicochemical properties of the melt.[1] Not only is it the foundation of studying the interface dynamics of the melt,[2,3] but also plays very important roles in optimizing and simulating the crystal growth craft. Moreover, it has been testified by theoretical analysis and experiments that the relationships do exist between the surface tension of the melt and parameters such as the gas isolation, the fining and inoculating effect, the surface roughness of castings, the graphite shape, etc.[4–6] The foundrymen carried out many attempts to evaluate the graphite shape of cast iron by its surface tension and made some progress in that area. Therefore, to study and fast measure the surface tension of the melt has important theoretical value and practical significance. Although many methods have been developed, they have not been adequate for fast measurement. Consequently, there is a need to develop a new method. In the present study, on the basis of further analyzing the maximum bubble pressure method, a new method for fast measuring the surface tension of the melt has been proposed and advanced. According to this new method, a device has been developed to fast measure the surface tension of the melt, by which the surface tension of the melt can be fast measured in 5 seconds. The quality of the melt has a decisive influence on the quality of the castings and therefore, on their usability. Thus, it is critical to ensure that the quality of the melt used is of a high standard. In recent decades, with the increase of the customer requirements on the physical DEQUAN SHI, Doctor, DAYONG LI, Professor, and GUILI GAO, Doctoral Student, are with the Department of Material Science and Engineering, Harbin University of Science and Technology, Harbin, Heilongjiang, People’s Republic of China 150040. Contact e-mail: [email protected] Manuscript submitted July 21, 2007. Article published online January 3, 2008. 46—VOLUME 39B, FEBRUARY 2008
and mechanical properties of the final cast product, the foundryman had to select the optimum methods to monitor the melt quality. To date, although many fast measuring and controlling techniques have been invented or developed, such as evaluating the microstructure of cast iron by the triangular sample method, determining the mechanical property, the graphite shape, and the modification effect by the thermal analysis method, and the specific resistance method, etc.,[7–9] the most commonly used techniques are the triangle sample method and the thermal analysis method. However, the measuring period of these two methods is much longer than 3 minutes because the solidification process has to be monitored. As a result, neither the triangle sample method nor the thermal analysis method can meet the requirements of testing speed and operative convenience. Therefore, there is a vital need to develop a new method. Theoretical analysis has shown that it is feasible to fast forecast the modification effect, the mold filling capacity, and the graphite shape by the s
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