境界要素法による鋳物の凝固解析と引け巣欠陥予測

概要

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Prediction of shrinkage cavity formation in shaped castings by the boundary element method was demonstrated with several examples. The five prediction parameters, i. e. (1) solidification time, ts, (2) critical fraction solid for fluid flow, fs_critical, (3) temperature gradient, G, (4) fraction solid gradient, fs_G, and (5) G/√R, were analyzed. A new parameter, "shrinkage potential," which includes amount of shrinkage cavity and porosity was proposed as a auxiliary parameter, for analyzing shrinkage cavity quantitatively. Since the amount of shrinkage cavity is mainly related to volume contraction during solidification of molten metals in casting processes, the shrinkage potential does not depend on the size or shape of the castings. By the use of this new parameter, the critical values of prediction parameters which depend on the size or shape of the castings can be determined automatically by computer simulation. It was found that solidification time mainly predicts the formation of shrinkage cavity around the region of the final solidification point ; and temperature gradient, fraction solid gradient and G/√R mainly predict the formation of internal porosities. Therefore, combined use of the prediction parameters, ts and G, and a auxiliary parameter, shrinkage potential, is necessary for predicting the formation of all types of shrinkage defects in shaped castings.
日本鋳造工学会の論文