Bifilm defects in ductile-iron support bracket castings

Abstract

Many filling defects such as bi-film defect, gas bubble, loosed sand and etc., are developed by turbulent filling. These defects entrapped and flowed along mold cavity during the filling process. As a result, they makes casting property unreliable and unpredictable. The best way to prevent the filling defect is to control the gating velocity under a critical value using a bottom gating runner system. Two different gating system, top- and bottom- systems, are applied for casting ductile-iron support bracket. For these two runner systems, their filling defects are predicted by a numerical modeling. Two- and three- parameter Weibull probability are plotted to analyze the reliabilities of the mechanical properties of the castings from these two gating systems. A good and reliable runner system for casting a high elongation and fracture toughness of the support bracket was proposed in this study.