铸造充型过程中液固转变影响流动行为的数值计算  

Numerical Simulation of Liquid-Solid Conversion Affecting Flow Behavior During Casting Filling Process

作　　者：曹流[1] 孙飞[1] 陈涛[1] 滕子浩 唐玉龙[1] 廖敦明[1] 

机构地区：[1]华中科技大学材料成形及模具技术国家重点实验室,武汉430074

出　　处：《金属学报》2017年第11期1521-1531,共11页Acta Metallurgica Sinica

基　　金：教育部新世纪优秀人才支持计划项目No.NCET-13-0229;国家数控重大专项项目No.2012ZX04010-031~~

摘　　要：为准确预测浇不足及冷隔,在已有的处理液固转变方法基础上,提出基于固相率变化的糊状区流动行为计算模型,该模型可以有效地处理液固转变过程中糊状区不同阶段的流动行为,即高固相率糊状区采用临界固相率方法,低固相率糊状区采用变黏度方法,中等固相率糊状区采用多孔介质拖拽模型。模拟了S型铸型水模拟实验,模拟结果与实验结果吻合很好,验证了不考虑液固转变时所采用模型的准确性。针对简单形状的底注式铸造工艺,对比分析了处理液固转变过程中采用不同控制参数的计算效果,证明了糊状区流动行为计算模型的合理性。Misrun and cold shut are common defects in casting productions, which could make sur- face accuracy of castings poorer, even leading to cracking and casting scraps in them. The formation pro- cess of misrun and cold shut is hard to be observed directly only by experiment measures, since casting filling process is in a state of high temperature flow inside mold. The key to predict the defects accurately is the way to handle the effect of liquid-solid conversion on flow behavior. On the basis of existing meth- ods for treating liquid-solid conversion, a calculation model of mushy region flow behavior through mea- surement of solid-fraction is developed, which can effectively investigate the flow behavior of mushy re- gion in different stages. Generally, the critical solid-fraction method is adopted for mushy region with high solid-fraction, in consideration of that only the speed of high solid-fraction region is supposed to be zero during casting filling process. The variable viscosity method is applied for mushy region with low solid- fraction, due to casting filling process being unlikely to form toothpaste-like flow. However, the porous me- dium drag-based model is used for mushy region with middle solid-fraction, because only the middle solid- fraction region can be equivalent to porous medium. Combining the above three methods, a flow-field cal-culation program considering the effect of liquid-solid conversion on flow behavior during casting filling process is developed, in which finite volume method （FVM） is included for discretization equations; the pressure implicit with splitting of operator （PISO） algorithm is added for coupling pressure and velocity; the volume of fluid （VOF） algorithm is also combined for interface tracking. An numerical simulation of water-filled S-shaped channel is performed in the case of taking no account of liquid-solid conversion, and the simulated results coincide better with the experimental results, which certifies for its accuracy as an adopted model. Since the bot

关 键 词：液固转变 糊状区 多孔介质 变黏度 有限体积法 数值模拟 

分 类 号：TG245[金属学及工艺—铸造]