Cast iron plays an extremely important role in China’s national economy and even in the world’s manufacturing industry. It is the most widely used casting metal material in industrial production. It plays a fundamental role in the general machinery manufacturing, metallurgical mines, petrochemical industry, transportation, national defense industry and other sectors. Although modern cast iron is faced with challenges from all aspects, there will still be great development in Austempered Ductile Iron,, vermicular cast iron, high-strength thin-walled gray iron and cast iron with various properties (such as anti-wear, anti-wear, corrosion resistance, etc.). Although China is in rapid development, cast iron will grow at a much higher speed than the world average level. However, the proportion of high-performance cast iron in China is far lower than that in the developed countries, and its properties are relatively poor. For example, although the output of malleable cast iron ranks first, most of them are black core malleable cast iron, while the output of white core malleable cast iron and pearlite malleable cast iron is not high. Therefore, it is important to study the properties of high-performance cast iron in order to realize the transformation from a big foundry country to a powerful one.
The properties of the material depend on its microstructure, so the research on the properties of cast iron needs to focus on the structure of cast iron (graphite + matrix structure), especially the high-performance cast iron. For example, the properties of cast iron are largely related to the number, size, distribution and morphology of graphite, especially the morphology of graphite. When the matrix is pearlitic cast iron and graphite changes from coarse flake (gray cast iron) to spherical (nodular cast iron), the tensile strength, elongation and impact toughness are greatly improved. Another example: after the castings are heated to austenitizing temperature to obtain uniform austenite structure, the castings are quenched into a salt bath, and remain in the salt bath at an isothermal temperature. Ferrite structure is precipitated from the austenite during the isothermal stay process, thus forming the Austempered nodular cast iron. Another example: after the graphite morphology is mixed by vermicular and spheroid in different proportions, the mechanical and physical properties of vermicular graphite cast iron are between gray iron and nodular iron. Therefore, how to quantitatively study and analyze the microstructure is an important way to control and improve the properties of cast iron. Numerical simulation is an important method to realize quantitative tissue morphology analysis, which has the characteristics of high experimental adaptability, high repeatability and low cost . Therefore, during the 13th Five Year Plan period, it is necessary to study the numerical simulation of the solidification and heat treatment of high-performance cast iron.
The coupling numerical simulation technology of multi-scale macro and micro structure of high-performance cast iron is mainly to grasp the evolution rule of the structure of graphite and matrix in the solidification and heat treatment of high-performance cast iron, so as to achieve the purpose of quantitative control and improvement of the properties of cast iron materials. For austempered ductile iron, the numerical simulation of the formation process of high carbon austenite and acicular ferrite structure of cast iron heat treatment is needed; for ductile iron, the numerical simulation of the formation of graphite spheroidized morphology under the action of spheroidizing agent and inoculant is needed; for vermicular iron, the numerical simulation of the formation process of graphite spheroidized morphology under the action of Vermicular Agent is needed, The multi-scale mathematical model and numerical simulation of the microstructure of vermicular graphite. The three kinds of typical high-performance cast iron are taken as the research object to make a breakthrough, grasp their rules and extend them to the numerical simulation of other high-performance cast iron microstructure evolution process, so as to form the multi-scale macro-micro structure coupling numerical simulation system technology of high-performance cast iron.
(1) Target to be achieved by 2020:
The multi-scale numerical simulation technology of macro and micro structure coupling of austempered ductile iron is realized, and the microstructure evolution rules of solidification and heat treatment are mastered.
(2) Target to be achieved by 2025:
The multi-scale numerical simulation technology of macro and micro structure coupling of nodular cast iron is realized, and the rule of microstructure evolution in the process of solidification and heat treatment is mastered.
(3) Target to be achieved by 2030:
The multi-scale numerical simulation technology of macro and micro structure coupling of vermicular cast iron is realized, and the microstructure evolution law of solidification and heat treatment of vermicular cast iron is mastered.