With the rapid development of my country's economy and the introduction and absorption of foreign high-end castings, the high-performance, high-efficiency, and high-reliability equipment in various fields has increasingly increased the quality of castings. Due to its high impact toughness at low temperature, low-temperature impact ductile iron materials have been widely used in wind power, high-speed rail and other fields. In recent years, the field has continued to develop, and the quality requirements for castings within and outside the industry have gradually reached an agreement, committed to the development of high toughness ductile iron at -40 ℃ or even -50 ℃. The quality of castings has a bearing on the safety, quality and life of equipment. The decisive influence. Our company is a professional cast iron manufacturing company jointly established by Henan Diesel Engine Heavy Industry Co., Ltd. and Shanghai 711 Research Institute. It has always been adhering to the principle of improving product quality and quality first, and putting quality stability and consistency as the top priority of management Heavy. The gear box body material produced by our company is EN GJS400-18LT, which is a typical thin-walled ductile iron shell casting. Its dimensional accuracy, weight, internal quality and other requirements are very high. There are certain difficulties in the casting process, and it can reach -40 in the as-cast state. ℃ impact toughness is even more difficult among the difficulties.