Experimental Examination of Method for Estimating Solid Fraction at Flow Cessation from Flow Velocity of Molten Al-Si-Mg Alloy

The purpose of this study was to experimentally estimate the solid fraction at which the cessation of the flow of a molten Al-Si-Mg alloy (JIS-AC4C) occurs in casting. The flow cessation mechanism of JIS-AC4C is known as the “mushy” formation type, which means that the flow ceases when the solid fraction at the molten metal tip reaches a certain critical value. Therefore, the flow velocity at the molten metal tip is assumed to decrease gradually. Thus, a new method for calculating the solid fraction at flow cessation based on computer simulations was examined using experimental measurements of the flow velocity and flow length. As a result of the experiment, the flow length became longer as the mold temperature and molten metal temperature increased. The flow velocity gradually decreased from the initial stage, but there was a region where the velocity was almost constant after the initial stage. The molten metal temperature became lower from the root side to the tip side, and the solid fraction at the time of flow cessation was calculated from the measurement results, and it was approximately 0.35-0.4 near the tip. Computer simulations were performed by tuning the heat transfer coefficients so that the flow length and flow velocity would match the experimental results and could simulate the changes in flow velocity obtained from the experiments. The solid fraction at the tip of the molten metal was almost the same as the experimental results. These results showed that it is possible to estimate the solidus fraction at the flow cessation from the flow velocity at the tip. It is easier and more accurate to calculate the flow ceased solid fraction by measuring the flow velocity of the molten metal tip. As a reference value, we were able to improve the calculation accuracy by comparing and verifying the flow ceased solid fraction calculated by the conventional calculation method from temperature.