The results show that the cooling rate of heavy section vermicular graphite cast iron is slow and the undercooling degree is low. After inoculation, the molten iron forms a small number of nuclei at a very small undercooling degree, which prevents the molten iron from supercooling to a temperature where more cores can be formed, resulting in coarse graphite and low casting performance; Because of the long time from the end of vermicularization to pouring, it is easy to cause the decline of vermicularization, so it is difficult to stabilize the production. By using wire feeding method to produce vermicular graphite cast iron, strict control of each process link, casting production process from extensive to fine management, supplemented by advanced thermal analyzer technology and practical ultrasonic technology, at present, has achieved stable production of more than 30 kinds of engine cylinder block, cylinder head and other castings.
With the high-quality development of enterprises, vermicular graphite cast iron is the first choice for some high-end engine materials, especially for the cylinder block, cylinder head and other castings of large high-end engines (M55, wh20, wh25, etc.).
Through tackling the technical difficulties of vermicularization equipment, composition of cored wire, vermicularization treatment process and vermicularization decline one by one, the special material of vermicular graphite cast iron was selected, and the production breakthrough of thick and large section vermicular graphite cast iron was realized.