Papers by Keyword: Nodule Count

Abstract: The graphite nodule count, size distribution and homogenization of the nodules distribution are the factor which are of more significance for the properties of the material. By just increasing the inoculants or Mg will not help to get rid of problems like the un-even size distribution and or increasing the nodule count. The cooling conditions of the melt prior to solidification and during solidification can control these two parameters to a large extent. In this research, it is more emphasized on the nucleation sequence of MgO particles and on the cooling rates. The nucleation of MgO at different temperatures and at different cooling rates was found to have a great influence on the nodule size distribution and the homogenization of the microstructure. A mathematical model was derived to relate the Mg concentration in the liquid to the cooling rate, prior to solidification. The MgO particles count was calculated as a function of cooling rate. It was found that at higher cooling rates, MgO can be nucleated in multi steps during cooling process, which can increase the nodule count tremendously.

Abstract: In this work the effects of stirring/vigorous shearing on matrix and graphite phase in nodular cast iron melt during solidification were studied. Several experiments were conducted for different cooling and stirring times. Samples were prepared and examinations of the microstructure were conducted and compared using Leica Optical Microscope and Scanning Electron Microscope (SEM). In addition, a chemical analysis of the graphite precipitate was performed using EDX equipment mounted on SEM. Oxidation of the melt and formation of oxide nuclei during stirring were observed and analysed. The influence of melt shearing on the structure, nodule count, distribution, area fraction and on overall graphite precipitation was observed and examined with the help of respective computer programs and soft wares. Stirring resulted in increasing the nucleation sites for graphite precipitation thereby increasing the nodule count and area fraction of carbide and transforming the structure from pearlitic matrix to ferritic matrix.

Abstract: The volume changes during solidification of Nodular Cast Iron (NCI) in the sand mold studied using Linear Variable Differential Transformer (LVDT). Both hypo- and hyper-eutectic compositions are considered by adjusting the carbon fraction in the composition during the experimental studies. The microstructural analysis and measurements are taken from the samples to evaluate the different phases present, the nodule count and size distributions. At the beginning of solidification, the experimental result shows the volume change is negligible. During the eutectic growth, the samples expand until the end of solidification. The displacement measurement shows the expansion continued when solidification finished. The volume change studies during solidification indicate that as the carbon fraction increases the volume expansion decreases. On the other hand, it is found that the pore fraction decreases as the volume expansion decreases. The fraction of primary austenite decreases as the fraction of carbon increases, and that leads to having a lower pore fraction.

Abstract: Mechanical properties of ductile iron casting are strongly inclined with metal matrix microstructure, graphite elements presence and impurities rate. Increasing in the number of graphite elements near to sphere shape (nodule), more superior mechanical properties will be realized. Automotive castings normally produced in mass production due to high demand; vertical moulding configuration is one of the best options for producing mass quantity automotive castings. This study aim to discover either the vertical moulding configuration will affects the nodularity properties distribution for different cavity position in the mold. In this study, ductile iron disc brake castings have been produced by in-mold Mg treatment using vertical parted molding method. Samples from different cavity position were taken and analyzed their nodularity distribution. Image processing computer procedure-Lieca was used to characterize the graphite morphology of the samples. The result shows that the different cavity position of vertical orientation disc brake casting produced dissimilar distribution of graphite. Higher position of cavity has higher nodule count and round graphite.