@article{Riposan2008, 
author = {Iulian Riposan and Mihai Chisamera and Stelian Stan and Torbjorn Skaland},
title = {Surface Graphite Degeneration in Ductile Iron Castings for Resin Molds},
year = {2008},
journal = {Tsinghua Science and Technology},
volume = {13},
number = {2},
pages = {157-163},
keywords = {ductile iron castings, surface graphite degeneration, resin mold, sulphur, oxygen, nitrogen},
url = {https://www.sciopen.com/article/10.1016/S1007-0214(08)70028-2},
doi = {10.1016/S1007-0214(08)70028-2},
abstract = {The objective of this paper is to review the factors influencing the formation of degenerated graphite layers on the surfaces of ductile iron castings for chemical resins-acid molding and core-making systems and how to reduce this defect. In the resin mold technique the sulphur in the P-toluol sulphonic acid (PTSA), usually used as the hardener, has been identified as one factor causing graphite degeneration at the metal-mold interface. Less than 0.15% S in the mold (or even less than 0.07% S) can reduce the surface layer depth. Oxygen may also have an effect, especially for sulphur containing systems with turbulent flows in the mold, water-bearing no-bake binder systems, Mg-Silica reactions, or dross formation conditions. Despite the lower level of nitrogen in the iron melt after magnesium treatment (less than 90 ppm), nitrogen bearing resins have a profound effect on the frequency and severity of surface pinholes, but a limited influence on surface graphite degeneration.}
}