DIRECT OBSERVATION AND NUMERICAL SIMULATION OF MOLD FILLING

摘要

Although a lot of works on numerical simulation of mold filling have been reported, then-accuracy has not been so clear, because of the difficulty of direct observation of mold filling. This paper presents direct observation results of mold filling and comparison with simulation. In the direct observation X-ray absorption images of the cast iron melt flow in sand molds were recorded with a high-speed digital video camera. In particular, the effects of gating systems on the filling behavior into cavities were investigated. In the numerical simulation, the governing discrete equations for the momentum, mass and energy conservation laws have been derived by the DFDM (Direct - Finite - Difference - Method). The observation results revealed the followings; even the same casting condition could not realize the same mold filling in details; a lot of gas was entrapped during mold filling and most of them disappeared with the melt flow, much smaller sprue cross-section and higher back pressure can realize much smoother mold filling without gas trapping, etc. Although the computer simulation roughly agreed with observed ones, it was difficult to well simulate flow separation on curved surfaces, detailed wavy free surface and flow change in the similar pouring.