立式离心铸造液态金属中气泡的长大规律

Gas Bubble Growth in Vertical Centrifugal Casting Liquid Metal

对立式离心力场下液态金属中的气泡长大过程进行了理论研究,推导出了气体原子向气泡中运动时的传质速度和扩散通量表达式。结果表明,气体原子向气泡中运动分为3个阶段,第一阶段气体原子从液态金属内部析出并向气泡表面迁移;第二阶段气体原子从溶解状态转变为吸附状态,并在吸附层中发生反应生成气体分子;第三阶段气体分子扩散进入气泡内。气体原子向气泡中运动时的传质速度和扩散通量均随着旋转角速度和离心半径的增加而减小。同时给出了当气泡内外压力相等时,气泡半径与旋转角速度和离心半径的定量关系式。

Formula of mass transfer speed and diffusion flux was established during gas atom moving towards gas bubble by theoretically analyzing gas bubble growth in vertical centrifugal casting liquid metal.The results show that gas atom moving towards gas bubble can be divided into three stages.At the first stage,gas atoms diffuse from the inner of liquid metal towards the surface of gas bubble.Gas atoms transfer from solution to absorption and react into gas molecules in the absorptive layer at the second stages.Gas molecules diffuse into the gas bubble in the final stage.The mass transfer speed and diffusion flux of gas atoms diffusing into the gas bubble can be decreased with increasing in the centrifugal angular velocity and radius.In addition,a quantitative equation between the gas bubble radius and the centrifugal angular velocity as well as centrifugal radius is established for the gas bubble with the internal pressure equal to the external pressure.