The creep effect of rare earth was found in the process of treating nodular cast iron with rare earth, but it was only treated as a “defect” at the beginning. Vermicular cast iron was first reported in morrogh’s works in 1948, but China began to study vermicular cast iron in the early 1960s. Rare earth is an important element in the chemical agent. In addition to the vermicular effect, it also has the functions of deoxidation, desulfurization and improving the candlelight resistance of vermicular cast iron.
The addition amount of rare earth as Vermicular Agent has a sudden change critical point. Beyond this critical point, the properties of gray cast iron will change suddenly. The pig iron was treated with vermicular agent prepared by mixing rare earth magnesium alloy and rare earth iron. It was found that when the amount of Vermicular Agent was 0.3%, the graphite morphology was A-type graphite and a small amount of C-type graphite; With the increase of vermicular dose, the graphite morphology gradually changed to supercooled D and E-type graphite and a small amount of star graphite, and approached the vermicular shape; When the amount of rare earth Vermicular Agent is 0.5%, the graphite is short, thick and curved. It is vermicular graphite and a small amount of spherical graphite, and its length width ratio is 3-7. The proportion of vermicular graphite reaches 65%. When the Vermicular Agent is added, the proportion of vermicular graphite will gradually decrease.