消失模铸造充型过程中的气膜压力及其厚度的数值模拟

Numerical Simulation of the Pressure and Thickness in Gas Gap in Lost Foam Casting Process

采用数值模拟方法,通过模拟板形灰铸铁件的消失模铸造充型过程,分析了各种工艺因素对充型过程中的气膜压力和气膜厚度的影响。结果表明,液态金属充型的驱动力并非重力而是消失模的退让速度,而这一速度是由气膜压力和气膜厚度的相互自动变化来调节,使充型达到稳态。结合理论计算,得到底注式浇注时充型可达到稳态,且气膜厚度和气膜压力随浇注温度、模样密度、涂料层厚度的增大而增大,随负压度和涂层透气性的增大而减小。

Through the simulation of the filling process of LFC（lost foam casting） gray cast iron plate castings,influences of various processing factors on the pressure and thickness in gas gap in lost foam casting process were analyzed by a numerical simulation method.The results show that the filling ability of molten metal is dependent on the speed of the foam decomposition rather than its gravity.The speed is adjusted by automatic change of the pressure in gas gap and gas gap thickness each other.Finally,the mold filling becomes steady-state.The steady-state filling of the molten metal can be realized with the bottom pouring by combining with the theoretical calculation.And the pressure thickness and in gas gap are increased with the increase of the pouring temperature,the pattern density and thickness of coating,and they are decreased with the increase of vacuum rate and coating permeability.