A Study on the Formation of Abnormal Structures in the Furan Resin Mold Interface of Spheroidal Graphite Cast Iron

In became clear in the preceding reports that para-toluen sulfonic acid which have been used as hardening catalyser on the furan resin mold release several types of sulfur system gases by thermal decomposition. An abnormal structure is formed on the interface of castings by interface reaction between sulfur system gases and spheroidal graphite cast iron melts. This is a paper on the abnormal structure studied from the behavior of magnesium, sulfur and manganese on the interface of castings. It was found that there is a remarkable concentration of residual magnesium, sulfur and manganese in the neighborhood of the interface where the abnormal structures appear. Magnesium and manganese in the melts react with sulfur in the pyrolytic gases of the furan mold until solidification completes on the surface layers of castings. Therefore, magnesium sulfides and manganese sulfides were formed, both of which were concentrated in the neighborhood of the interface of castings. The effective magnesium contents for graphite spheroidization decrease with the reaction on the interface of the casting and mold, and form abnormal structures on the interface.