Casting is a traditional and ancient production technology with a history of more than 4000 years. China is a big country in foundry production. According to relevant reports, China casting production in 2017 has reached 28 million tons, ranking first in the world. With the gradual transfer of manufacturing from developed countries such as Europe and the United States to developing countries such as Southeast Asia and regions, China casting industry will develop on a larger scale and at a faster speed. At present, China casting production technology level is still very backward, and the per capita output value is less than 50000 yuan. Therefore, in order to become a World Foundry power, we must innovate, adopt new technology and master the key core technology. The foundry process includes complex transfer of heat, quality and momentum. There are many influencing factors in such a complex transfer process, so we can only establish a mathematical model and use computer simulation, Simulate various phenomena in the China casting process. And summarize the law, so as to guide the production practice.
Numerical simulation is also computer simulation. It refers to using a set of control equations to describe the change relationship of the basic parameters of a process, obtaining the quantitative understanding of the process through numerical solution, and optimizing the process or predicting casting defects through dynamic simulation analysis of the process. In recent years, with the rapid development of computer technology, many casting software came into being. Many famous foundry enterprises have adopted these software, and the effect is very obvious. They improve the quality of castings and reduce a lot of production costs at the same time. In the United States, many research institutions and universities have adopted numerical simulation methods to design high-tech products such as cars, aircraft and missiles, and it is becoming more and more common. According to relevant reports, using numerical simulation method to design the China casting process can shorten the trial production cycle of the whole product by 40%, reduce the production cost by 30% and improve the utilization rate of all materials by 25%.
Over the past two decades, all countries have shown great interest in numerical simulation and invested considerable human, financial and material resources. Chinese foundry researchers have conducted in-depth research on many phenomena in the casting process and achieved considerable results. The computer simulation of the China casting process mainly includes the following main aspects:
(1) Flow field simulation: numerical simulation of casting filling process. It mainly uses the principle of hydrodynamics to analyze the mold filling process of castings, so as to optimize the gating system and predict the defects such as air entrainment, slag inclusion and erosion.
(2) The simulation of temperature field is the numerical simulation of casting solidification process. It mainly uses the principle of heat transfer to analyze the heat transfer process and interface heat transfer process of castings, and simulate the cooling and solidification process of castings, so as to predict the possible casting defects such as shrinkage cavity and porosity.
(3) Stress field simulation: Based on the mechanical principle and temperature field simulation, analyze the stress distribution of the casting and predict the possible defects such as hot crack and deformation. The thermal stress numerical simulation of the solidification process of the casting can also analyze the residual stress and residual deformation of the casting, so as to provide a basis for controlling the dimensional accuracy of the casting.
(4) Coupling simulation of flow and heat transfer: Based on the principle of hydrodynamics, the heat transfer is calculated while simulating the mold filling process, which can predict the possible casting defects such as insufficient pouring and cold lap.
(5) Microstructure simulation: it can be divided into macro and micro microstructure simulation. It mainly uses some mathematical models to calculate the number of liquid nucleation, dendritic growth rate and microstructure transformation of the alloy according to the principle of solidification, so as to predict the casting performance. Numerical simulation of the formation process of solidification structure of the casting can help to predict the mechanical properties and as cast structure of the casting, The quantitative relationship between the main process parameters and solidification structure can be obtained, which can provide a reliable basis for improving the microstructure of castings through process control.