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 catalyst. 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 ferrosilicon. 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 turns to supercooling, and D and E-type graphite and a small amount of star graphite are close to 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. Its length width ratio is, in which the number of vermicular graphite accounts for 65%; When the Vermicular Agent is added again, the proportion of vermicular graphite will gradually decrease.