Research status of high strength and toughness alloying of nodular cast iron

The tensile properties of nodular cast iron are mainly related to the quantity and quality of graphite balls and the proportion of each phase in the matrix. In recent years, with the rapid development of China’s industry, the demand for high strength and Toughness Nodular Cast iron is increasing. The methods to improve the strength and toughness of nodular cast iron mainly include heat treatment and alloying. However, due to the complex process of heat treatment to improve the properties of nodular cast iron, the research direction of improving the strength and toughness of nodular cast iron by alloying has attracted extensive attention, and many achievements have been obtained at present:

Sun Lixi et al. Prepared high-strength nodular cast iron by adding trace elements Sn and sb into the molten iron. It was found that when adding 0.03 wt.% Sn and 0.012 wt.% sb into the molten iron, nodular cast iron with tensile strength of 805 MPa, hardness of 290 Hb, elongation of 4.6% and impact toughness of 32 J / cm2 could be obtained, which met the performance requirements of die materials for automobile panels. Based on the existing QT600-3 brand in China, Chen Zhongshi and others strengthened the matrix structure through Cu and Sn alloying elements by using scrap carburization technology, and prepared high-strength and toughness ductile nodular cast iron with tensile strength ≥ 600 MPa and elongation ≥ 10%. J. Lacaze and other scholars studied the effects of Cu and Sn on the microstructure and properties of medium manganese as cast nodular cast iron. It was found that when the addition of Cu was 0.47 wt.% and SN was 0.066 wt.%, high-performance nodular cast iron with tensile strength of 987 MPa and elongation of 5.1% was obtained. Liu Yong studied the effect of micro alloying element Te on the microstructure and properties of nodular cast iron. It was found that te could increase the content of pearlite in the matrix and refine the lamellar spacing of pearlite. Finally, the as cast nodular cast iron with tensile strength higher than 800 MPa and elongation not less than 5% was developed by alloying treatment combined with waste heat normalizing treatment. Ge Weifeng et al. Adjusted the content of nickel and manganese alloy elements on the basis of the composition of qt400-18 nodular cast iron, and obtained a new type of nodular cast iron whose comprehensive properties of strength and low-temperature toughness reached the use standard of wind power parts.

Looking at the above research results, it can be found that the performance of nodular cast iron can be improved by alloying means combined with appropriate treatment process. However, due to the high price of many alloying elements, the development of alloyed high strength and Toughness Nodular Cast iron is limited to a certain extent. In the future, it will be a new research trend to improve the strength and toughness of nodular cast iron by cheap alloy elements.

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