In order to have an effective understanding of vermicular graphite cast iron technology, we must have a comprehensive understanding of its graphite growth state and production mechanism. The graphite in vermicular graphite cast iron is called vermicular graphite cast iron because its production state is vermicular. During the growth process of vermicular graphite, the transformation growth is often completed in different directions, and there are related branches in the growth process, including lateral branches and edge branches. In the interior of vermicular graphite cast iron, the graphite of vermicular graphite cast iron will move to a certain extent. Because of its high similarity with worms, it is also called “vermicular graphite”.
During the growth process, the front end of vermicular graphite presents several branches, some of which are round; Some branches show sharp shape, the whole structure contains a large number of thick flake graphite, with distinct characteristics. At the same time, vermicular graphite itself has great differences, in fact, graphite morphology is usually very characteristic. For example, when the content of magnesium in the molten iron is high, the graphite state in the vermicular graphite cast iron can be closer to the spherical graphite; When the content of magnesium is low, the vermicular graphite of vermicular graphite cast iron tends to flake graphite. In the field of industrial application, in order to ensure the effective application of vermicular graphite cast iron technology, it is necessary to effectively control the trace elements in the molten iron to keep its intermediate performance and realize effective transformation. In addition, the graphite crystallization in vermicular graphite cast iron can be divided into two stages.
First, the graphite crystal can react with the external environment in the solidification process to form primary graphite. In some fields, primary graphite is widely used;
Secondly, the vermicular graphite in vermicular graphite cast iron will increase gradually with the solidification process during eutectic solidification. At the same time, eutectic graphite is formed with austenite and ledeburite eutectic. Graphite has its own distinctive characteristics in the growth process, such as not surrounded by austenite, and the content gradually decreases, which changes its own growth mechanism and direction. Like other cast iron technologies, the solidification characteristics of vermicular graphite cast iron depend on the eutectic growth mode.