【作者】 吴凯；

【导师】 周建新； 殷亚军；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2016， 硕士

【摘要】 消失模铸造作为一种近净成形技术,凭借其绿色环保、效率高、成品质量好等优点,在实际铸造生产过程中具有广阔的应用前景。灰铸铁消失模铸造是消失模铸造的重要组成部分。然而在灰铸铁消失模铸造过程中,模样受到金属液热作用分解产生气体间隙,会对整个铸造充型凝固产生重要的影响,使得其铸造过程中的物理场异于传统铸造方式,工艺方案制定较为困难。本文主要研究了消失模铸造过程的界面推移模型、离散求解技术和热物性参数数据库,开发了灰铸铁消失模铸造数值模拟系统,可以为工艺人员制定最终消失模铸造工艺方案提供参考。首先,建立了灰铸铁消失模铸造的数学模型。在分析已有的界面推移模型基础上,液流前沿的压力边界采用计算所得气隙压力,建立了消失模铸造的界面推移数学模型;在计算流体力学和数值传热学的基础上,建立了传热、流动耦合的流动场、温度场数学模型。并对消失模铸造模拟过程中的物理场的边界条件进行了探讨。其次,完成了对灰铸铁消失模铸造数学模型的离散求解。基于有限体积法离散消失模铸造流动场和温度场控制方程,采用SOLA-VOF法对充型过程进行数值求解;并探讨了消失模铸造数值计算的稳定性条件。然后,建立了灰铸铁消失模铸造的热物性参数数据库。设计了灰铸铁阶梯件消失模铸造凝固测温实验,分析阶梯件消失模铸造凝固过程6个不同位置点温度曲线,并将其与模拟曲线进行对比。设计了正交实验,获得最佳热物性参数,使模拟结果和实际测温数据相吻合。最后,基于华铸CAE开发了灰铸铁消失模铸造数值模拟系统并完成了对模拟系统的验证和应用。通过对灰铸铁试验件消失模铸造过程模拟分析验证了模拟系统的可靠性。应用灰铸铁消失模铸造模拟系统研究了壳体件的消失模铸造过程,分析了不同工艺方案下铸造缺陷最终分布状态,确定了最佳铸造工艺。更多还原

【Abstract】 As a near net forming technology, the lost foam casting(LFC) is taking an important place in the foundry due to its advantages of environment friendly style, high efficiency and high quality product. It has a wide application prospect. LFC production of gray cast iron is an important part in LFC application. However, in lost foam casting process of gray cast iron, the gas gap produced by decomposition and gasification of foam, have important influence on the filling and solidification, making the temperature field, flow field and pressure field of the whole process different from the traditional way of casting, making process control hard to realize. Therefore, this paper does research on the filling and solidification characteristics of LFC and focuses on development and application of lost foam casting simulation system of gray cast iron. The system can provide reference for technicians.First, mathematical model of lost foam casting is established in this paper. Through analysis of the existing interface shifting model and consideration of decomposition of the foam, the lost foam casting interface shifting model is realized by making the gas gap pressure as the boundary condition of the front metal flow. Based on computational fluid dynamics and numerical heat transfer, temperature model coupled with flow model of LFC is established. And the boundary conditions of the LFC simulation are discussed.Secondly, numerical calculation of LFC model is realized. Discrete equations of the lost foam casting model are solved by finite volume method, VOF method was used to capture the interface. And the numerical stability conditions of the LFC simulation are discussed.Then, thermos-physical parameters database for gray cast iron in LFC process is established. LFC solidification temperature experiment of grey cast ladder specimen is designed. The solidification temperature curve of six different points are analyzed and compared with the simulation temperature curves. Through the adjustment of single key factor, their influence on the solidification cooling curve is analyzed. A set of orthogonal experiment are designed to obtained physical parameters database for gray cast iron in LFC process, so that the simulation results and the actual temperature measurement data match each other.At last, LFC simulation system is developed based on InteCAST. And LFC simulations of gray cast iron specimen are implemented to study filling sequence and filling characteristics. Therefore, feasibility and reliability of the simulation system are proved. Then the simulation system is applied to simulate the casting process of LFC shell specimen and final distributions of casting defects of different technology schemes are analyzed. And the optimum casting parameters are determined. Thus, the feasibility of the simulation software and the mathematical model is verified. The software is capable of successfully simulating filling process and predicting defects distribution of LFC process, and providing design reference for the actual production quality control.更多还原