Abstract
This paper discusses a problem connected with the production process of ductile iron castings made using the in-mold method. The study results are presented showing that this method compromises the quality of the cast machine parts and of the equipment itself. Specifics of the nodularization process using the in-mold method do not provide the proper conditions for removal of chemical reaction products to the slag, i.e., the products stay in the mold cavity and they also decrease the quality of the casting. In this work, corrosion-type defects were diagnosed mostly on the surface of the casting and some compounds in the near-surface layer—i.e., fayalite (Fe2SiO4) and forsterite (Mg2SiO4)—which cause discontinuities in the metal matrix. The results presented here were selected based on experimental melts of ductile iron. The elements of the mold used in this study, the shape of the mixing chamber, charge materials, method of melting, temperature of liquid metal, etc. were directly related to the production conditions. An analysis was conducted of the chemical composition using a Leco GDS500A spectrometer and a carbon and sulfur Leco CS125 analyzer. Metallographic examinations were conducted using a Phenom-ProX scanning electron microscope with an EDS system.
Highlights
The aim of the article was to show the problems that arise from using the in-mold spheroidysation method
If a casting produced based on the nodularization process in-mold shows a tendency to corrode under storage conditions in a locked room, where the effect of corrosive factors is limited, it should be assumed that such castings exposed to varying temperatures, periodic humidity changes, etc. will undergo corrosion processes in a more violent manner
The authors [1] showed the production process of cast iron castings with vermicular graphite precipitates, where sulfur compounds were deliberately added into the liquid alloy
Summary
The aim of the article was to show the problems that arise from using the in-mold spheroidysation method. One of the most widespread methods for the production of castings from ductile and vermicular iron is the nodularization process in mold. At work, [1] presented a way of grey cast iron production with vermicular graphite based on the in-mold method. This type of cast iron requires knowledge about the cast iron metallurgical process because of the very restrictive amount of residual magnesium at 0.02%. Its metallurgical quality is high and the probability of the appearance of sulfide inclusions or of fayalite and forsterite is slight This is different for the in-mold nodularization method.
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