Evaluation of the Metallurgical Quality of Nodular Cast Iron in the Production Conditions of a Foundry

Abstract

The aim of this research was to determine the factors affecting the metallurgical quality of cast iron during serial production of castings using a campaign cupola and a holding furnace. The problem to be solved, which was to obtain cast iron with the required mechanical properties while reducing the internal porosity, results from the foundry’s need to increase the metallurgical quality of the alloy. The increasing difficulty and complicated constructions of castings, for which it is not possible to introduce risers at the stage of technological design, make the stage of proper preparation of cast iron the only way to obtain castings without shrinkage defects. The article presents the results of the study of physicochemical and mechanical properties, microstructure and shrinkage tendency of ductile iron depending on the charge materials used, the amount of Mg used during spheroidization and the type of final inoculants. Step castings and wedge tests were produced on a vertical molding line. The spheroidization was carried out by injecting a core wire containing Mg alloy into the cast iron. The final inoculation of 0.2% was performed using a pneumatic dispenser equipped with a vision system to control the effectiveness of the inoculation. The ITACA Meltdeck thermal analysis system was used to study the physicochemical properties of the initial cast iron, and the ITACA X system to analyze the state of the final cast iron on the molding line. Mechanical tests were performed on samples cut from a stepped casting, and microstructure tests were carried out using a light microscope and a scanning electron microscope. The results of thermal analyses show that increasing the share of pig iron at the expense of steel increases the minimum solidification temperature of eutectic, and thus, increases the potential for graphite nucleation in cast iron. Increasing the nucleation potential can be obtained by adding anthracite, FeSi and SiC. A very important factor in obtaining cast iron of high metallurgical quality is the possible limitation during spheroidization of the length of the core wire containing Mg, which is a carbide-forming element. The lower the initial sulfur level, the greater the possibility of reducing the amount of cored wire. The inoculants containing Ce and Bi were the most advantageous final inoculants from the point of view of obtaining the best microstructure parameters and plastic properties of cast iron.

Expansion and optimization of the nomenclature of certified reference materials for spectral analysis of cast irons

“…Одновременно с поддержанием действующей номенклатуры развитие металлургии [9,10] фор мирует запрос на новые образцы, позволяющие определять большее число элементов в более ши роком диапазоне содержаний.…”

A Methodology to Define the Niyama Criterion Reinforced with the Solid Fraction Analysis: Application to Sand Casting of Steel Bars

“…Due to the last limitation, Carlson and Beckermann [12] defined a dimensionless Niyama criterion. Other authors proposed other parameters, such as the rate of transition of the alloy from a semisolid to solid state, establishing for cast iron a strong relationship between that parameter and the formation of shrinkage cavities [13].…”

Regularities of Crystallization Heat Release During Solidification of Alloyed Cast Irons

“…One of the effective methods to study the crystallization process of metals and alloys is the differential thermal analysis (DTA) [6][7][8]. It allowed particularly to investigate the graphitization ability of spheroidal graphite cast iron processed by Al, Zr, Ca-FeSi [9], solidification influence in the control of inoculation effects in ductile cast irons [10], solidification pattern of Si-alloyed, inoculated ductile cast irons [11], the influence of final inoculation on the metallurgical quality of nodular cast iron [12] and an increasing precision and yield at casting production by simulation of the solidification process based on realistic material data evaluated from thermal analysis [13].…”