Effect of graphite morphology and distribution on properties of nodular cast iron

In recent years, with the development of mechanical equipment towards portability, low energy consumption and high efficiency, new requirements are put forward for the properties of nodular cast iron, especially low-temperature impact toughness. The conventional methods to improve the properties of nodular cast iron mainly include alloying and self structure optimization. The effect of Alloying on the properties of nodular cast iron has always been the focus of research, and a series of studies have been carried out at home and abroad.

Yu Guangyuan and lekakh studied the effect of Si element and content on the properties of nodular cast iron. The results show that Si can improve the strength and hardness of nodular cast iron, but the increase of Si element can increase the ductile brittle transition temperature and significantly reduce its low-temperature impact toughness. Lacaze et al. And sun et al. Studied the effect of Ni on the properties of nodular cast iron. The results showed that Ni could significantly improve the tensile strength and hardness, but had no obvious effect on the impact toughness at low temperature. Wang Wenhui et al. Studied the effect of Ni and Si element combination on the low-temperature impact toughness of nodular cast iron. The research results show that with the increase of Ni and Si content in the material, the low-temperature impact energy of low-temperature and High Toughness Nodular Cast Iron continues to decrease and the brittle fracture characteristics are intensified. Omran et al. Studied the effect of Mn on the properties of nodular cast iron. The results show that Mn can significantly improve the yield strength, but has no obvious effect on the tensile strength, and the increase of Mn content can significantly deteriorate its impact toughness.

In conclusion, the addition of alloy elements can not take into account all aspects of mechanical properties, especially low-temperature impact toughness, and even worsen the low-temperature impact toughness, and the cost of alloy elements is high. However, there are few studies on the relationship between the optimization of graphite structure and macro properties of nodular cast iron. Therefore, nodular cast iron with the same composition was prepared by different spheroidizing processes. The mapping relationship between different graphite structure and properties was studied by controlling the diameter and distribution of spherical graphite structure and the spherical regularity of graphite; At the same time, neural network calculation is used to establish the model of microstructure parameters and properties of micro graphite ball, so as to determine the weight ratio of graphite structure parameters on properties, optimize the properties of nodular cast iron, and provide data basis and technical support for industrial application.

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