The research on low-temperature impact toughness of nodular cast iron abroad started earlier, mostly concentrated in the United States, Germany, France, Denmark, Spain and other countries with more applications of wind power generation. These countries have not only developed different grades of nodular cast iron for low-temperature impact toughness, but also formulated corresponding nodular cast iron standards to guide the actual production and testing, such as DIN1693-1973 standard, BS2789-1985 standard, EN1563-1997 standard, etc.
Foreign research is mainly carried out from the aspects of chemical composition, heat treatment process and matrix structure of nodular cast iron. In terms of chemical composition, larker Richard of Sweden studied the solid solution strengthening effect of silicon and manganese on the matrix of nodular cast iron. It is found that with the increase of silicon, the tensile strength and hardness of nodular cast iron increase slightly, and the elongation decreases moderately. For every 0.1% increase in silicon, the tensile strength increases by 9.29mpa and the elongation decreases by 0.323%. Manganese can increase the yield strength of nodular cast iron and significantly reduce the elongation. For every 0.1% increase in manganese, the yield strength increases by 7.4mpa and the elongation decreases by 1.83%.
G. I. Silman et al. Studied the effect of cobalt on the mechanical properties of nodular cast iron. It is found that after adding an appropriate amount of drilling element, there will be a small amount of austenite in the matrix, the tensile strength will be reduced, but the toughness will be improved.
U. S. ekera et al. Studied the effects of nickel and copper on the properties of nodular cast iron. It is found that the alloying elements nickel and copper can not only improve the wear resistance and machinability of nodular cast iron, but also have a significant effect on its mechanical properties. After adding 0.6-0.7% copper, the matrix structure is mainly pearlite, the tensile strength and hardness are improved, and the impact toughness is reduced. After adding 0.5-1.12% nickel, a small amount of retained austenite appears in the matrix and the impact toughness is improved. The optimum addition of copper and nickel is 0.7%.