The molten iron enters the mold filling process through the gating system, which can be seen as a liquid with a certain viscosity moving in the mold, which conforms to the relevant laws of fluid mechanics
① There are complex thermal, mechanical and chemical reactions between high temperature molten iron and resin sand mold. For example, a large amount of resin sand gives off gas to form Blowholes in the casting under long-time high-temperature baking, the coating on the mold wall falls off at high temperature to form inclusions, the molten iron oxidizes to form oxide slag inclusion, and the viscosity and volume of molten iron change with the decrease of temperature.
② The molten iron is unstable during pouring. With the pouring process, the liquid level of molten iron in the mold rises continuously, and the liquid level difference between the molten iron in the runner cup or seat ladle and the molten iron in the mold decreases continuously, and the effective pressure head of mold filling is from 2500 mm With the rapid and large amount of gas evolution of resin sand, the air pressure in the mold increases greatly compared with the initial stage of pouring; due to the variability and difference of pouring operation, there are many uncontrollable changes in the filling process.
③ The molten iron is turbulent and multiphase flow in gating system and cavity. The distribution of the gating system in the intake cylinder is complicated due to the special casting. The factors such as section change, turning, filtering system and bifurcation of the gating system can not be excluded, which lead to the turbulence state of the molten iron. At the same time, the molten iron may be mixed with impurities, dregs, gas and precipitated grains, and the filling process shows multiphase flow state.