Based on the simulation analysis of the casting process of 100 ton ductile iron nuclear spent fuel container, the 45 ° sector test block was designed and the solidification temperature field of the 45 ° sector test block was measured. The microstructure and properties of the 45 ° sector test block were dissected and analyzed. The casting process of the ductile iron nuclear spent fuel container was optimized and improved

(1) Using sand mold casting process, the solidification time of ductile iron nuclear spent fuel container is as long as 50.64h, which obviously can’t meet the requirements; although the use of chill accelerates the solidification speed of ductile iron nuclear spent fuel container, the solidification time of ductile iron nuclear spent fuel container under sand mold and chill process is still as long as 25.88h, which still can’t meet the requirements, so Sand mold chill process can not be used; in the metal mold process, the solidification time of ductile iron spent fuel container is shortened to 3.49h, and the distribution of shrinkage defects is also greatly reduced, so the ductile iron spent fuel container adopts the metal mold casting process; in addition, the domestic and foreign ductile iron spent fuel containers do not use the metal mold casting process It is proposed that the ductile iron spent fuel container should adopt the metal mold casting process;

(2) The temperature field of 45 ° fan-shaped block was successfully measured by 16 channel temperature measurement system. By analyzing the temperature field of 45 ° fan-shaped block, it is found that the final solidification position is not the center of the block, but the inner quarter; the solidification temperature of large section ductile iron is not 1147 ° C, but in the range of 1147 ° c-1080 ° C; the actual temperature measurement results are consistent with the simulation results The current simulation software can be used to optimize the casting process of large-scale ductile iron spent fuel container;

(3) The results show that the spheroidization rate is more than 85%, the number of graphite balls is more than 50 / mm2, the matrix structure is full ferrite, the tensile strength is more than 371mpa, the yield strength is more than 233mpa, the elongation is more than 19.5%, and the impact value at – 40 ° C is more than 5.4j/cm2, all of which meet the requirements of ductile iron nuclear spent fuel container Under the existing technical conditions, it can reach the performance index of foreign ductile iron nuclear spent fuel container

(4) The number of graphite balls has little influence on the yield strength, tensile strength, elongation and other conventional mechanical properties, but has a great influence on the impact property, especially for – 40t: low temperature impact property, the number of graphite balls in the inner quarter is the least (50 / mm2), and the weak link of impact property at – 40 ° C is near the inner quarter In addition to optimizing raw materials, strictly controlling trace element content, proper spheroidizing and inoculation process, measures should also be taken to further accelerate the cooling of castings, so as to make them solidify in 3.5 hours, and ensure the number of graphite balls ≥ 50 / mm2;

(5) After optimizing the casting process of ductile iron spent fuel container, the 300 mm metal mold + 300 mm chill process is used in the body of the container, and the 450 mm metal mold + 450 mm full chill process is used in the top hot spot, which can not only ensure the solidification of the container in 3.5 hours, but also make the body of the container stable In order to ensure the consistency of microstructure and properties of the spent fuel container, the solidification temperature field of the hot spot should be coordinated.