In addition to the study of chemical composition, heat treatment process and metallographic structure, many studies have been carried out on trace elements in nodular cast iron in China. Xu Feng and others from Qiqihar No.1 Machine Tool Plant studied the metallurgical behavior of trace chain and antimony in large section ductile iron, and summarized the role of trace bleeding and antimony in large section ductile iron. Through the production experiment, it is determined that the appropriate dosage of secret and antimony in the production of large section ductile iron is 0.005% and 0.008% respectively. At this time, the graphite can be effectively refined, the spheroidization rate and the number of graphite balls can be improved, and the harmfulness of theory and antimony is quantitatively evaluated.
Zhao Yongqi, Shi Jupeng and others studied the application of chain and antimony in thick and large section ductile iron parts. The experimental results show that using 0.01% – 0.015% antimony and Si Ba Co alloy for flow inoculation can significantly improve the spheroidization rate of graphite and the roundness of graphite balls.
Cai Qizhou of Huazhong University of science and technology studied the effect of Yihe antimony on the graphite morphology of thick and large section nodular cast iron. The results show that yttrium forms a high melting point hexagonal system in molten iron. It can be used as the core of graphite ball. Combined with antimony, it can increase the number of graphite balls, fine fossil graphite balls and improve the roundness of graphite balls.
Liu Wei of Beijing Jiaotong University and others studied the effect of tin on the microstructure and properties of isothermally quenched nodular cast iron. Through the quantitative analysis of microstructure, micro composition and comparative experiment of mechanical properties of isothermally quenched nodular cast iron, it is found that a small amount of graphite increases the number of graphite balls per unit area. It can obviously reduce the segregation of manganese at the grain boundary and reduce the white bright area.
At present, many universities and foundry enterprises are still studying the low-temperature impact toughness of nodular cast iron, and strive to translate the research results into practical production. Many foundry enterprises have also transformed and gradually established a complete production line of low-temperature ductile nodular cast iron. The emergence of nodular cast iron for wind power fittings also urges the birth of a new standard of nodular cast iron in China. In March 2009, the standard GB / t1348-2009 for nodular cast iron was officially announced and implemented in September of the same year. Compared with the standard GB / t1348-1988, the new standard adds several grades of nodular cast iron for wind power fittings, makes clear provisions on the impact toughness of nodular cast iron, and makes up for the blank of the old standard in nodular cast iron for wind power fittings.