消失模铸造液流前沿气隙中的质能传输平衡判据及应用

Equilibrium Criterion and Application of Mass and Energy Transfer in Front of Metal Stream in EPC

运用基础理论计算消失模铸造金属液流前沿与消失模接触的界面上的排气能力与发气能力比η的数学表达式,当η≥1时,界面上的质能传输才能达到平衡;当η接近1时,才有可能生产出高质量的铸件。对壁薄、低熔点合金铸件,η一般都大于1,采取使其涂层的厚度、浇注温度、模样的密度、浇注速度增加,使得浇注系统的静压头、涂层的透气性、型内的真空度、铸件水平截面的周长减少,从而使η接近1;对壁厚、高熔点合金铸件,由于η值一般都小于1,为使其接近1,其措施与前者恰恰相反,经生产实践验证是正确的。

The rate of venting quality and gas evolution, η, at the space between molten metal and evaporated pattern was calculated based on theory in this paper. The mass and energy transfer is balanced at the interface only when η≥1. Quality castings can be produced only when η≈1. For thin thickness-wall and low melting-point alloy, generally the η is larger than 1. In addition some measurements, such as thick coating layer, high pouring temperature, high mold density and pouring velocity should be taken to reduce the pressure head, the venting ability, the vacuum degree of mold cavity and the profile length of casting, thus to make η approach to 1. For the thick wall and high melting-point alloy castings, generally the η is less than 1, the opposite measurements should be considered. These measurements have been testified by practical production.