Large section ductile iron has large wall thickness, heavy weight and long solidification time, especially at the center or hot spot (as shown in the figure); s, Mn and other elements are easy to segregate at the grain boundary, which reduces the plasticity and initial properties of large section ductile iron, and leads to the decline of properties of ductile iron, especially the low temperature impact property. The solidification mode of ductile iron is volume solidification, which is produced at the final solidification position The tendency of shrinkage defects is large.
The 100 ton ductile iron nuclear spent fuel container with 520 mm wall thickness, 630 mm hot spot thickness and 135 t weight has the solidification characteristics of large section ductile iron. The 100 ton ductile iron nuclear spent fuel container has longer solidification time, larger solidification heat and different solidification between the body and hot spot, which leads to the same microstructure and properties The above factors make it difficult to control the quality of 100 ton ductile iron nuclear spent fuel container. The quality control technology of nodular cast iron nuclear spent fuel container is known as the “pearl on the crown of nodular cast iron”, which is the watershed of the development level of a country’s nodular cast iron industry.