Papers by Keyword: Chill

Abstract: The paper presents a mathematical model and the elements of a computer program for calculation and visualization of solidification of the rotating molten iron of the working layer of the roll in the centrifugal machine. We established the dynamics of changes in supply rate of carbide nanopowder feeding on the surface of the molten metal, provided its uniform distribution along the solidifying layer of the cast iron. It is shown that the working layer of the iron cools sideways and more intensively from the side of the chill mould; the areas, which are located near it, are the first to reach the solidus and liquidus temperatures. During cooling the layer of the iron, a maximum of temperatures is observed at a distance of 25 – 30 mm from the protective flux contacting surface. It was established that for a uniform distribution of nanopowder in the solidifying layer of the iron its feeding supply rate needs to be proportional to the speed of the moving the front of particle penetration, which is defined by the solidification front. Powder feeding needs to start from the time concurrent with the start of moving the front of particle penetration into the metal and to finish when an opposite crystallization front begins to form from the side of the flux.

Abstract: Inoculation is a treatment applied to the liquid base iron, to supply one or more elements, such as Al, Ba, Ca, Zr, Sr, Ce, La etc. with active roles in developing graphite nucleation sites. The efficiency of inoculants is directly dependent on the sulphur level: lower sulphur, lower inoculating power or unpredictable results. The objective of this paper is to examine the effects of a S and O containing inoculant enhancer [S,O,Al,Ca-FeSi alloy] to conventional Ca,Ba-FeSi alloy, in the mold treatment of electrically melted grey iron at 0.035%S, 0.002%Al, 0.0005%Zr, (%Mn) x (%S) < 0.02. The wedge test samples [W3 – ASTM A367] were used to evaluate the influence of the cooling rate and inoculation on the carbides formation. It was re-confirmed that for above mentioned critical chemistry conditions, this iron is sensitive to chill formation, despite the carbon equivalent level at 3.8%. Inoculation enhancement increased the effectiveness of the Ca,Ba-FeSi standard inoculant.

Abstract: Main objective of the present work is to investigate the effect of dispersiod content and the effect of chill on the mechanical properties of chilled MMC with LM25 as matrix and SiO₂ as dispersoid. Investigation is carried out to evaluate Ultimate Tensile Strength (UTS), Fracture toughness, Hardness, and microstructure of chilled aluminum matrix and Glass particulate composite. The glass (SiO₂) particles ranging from 30-to100µm were chosen as dispersiod and added, ranging from 3to 12wt% in steps of 3%. The composite was prepared by stir-casting technique and poured into the sand molds incorporated with non-metallic and metallic chills. Test result showed that this MMC was greatly influenced by the dispersiod and chills. Fracture toughness & UTS of the composite are found to depend on the wt% of the dispersiod and chilling medium. It is observed that chill has influenced hardness of the composite. Volumetric heat capacity (VHC) of the chill is found to increase the amount of heat absorbed. Microstructure analysis has reveled uniform distribution of the dispersiod, which results in improved properties of the particulate reinforced metal matrix composite.

Abstract: Forced cooling measures need to be adopted in order to ensure the thick walled ductile iron casting solidification within the stipulated time. In this paper, the thick walled ductile iron casting for spent-nuclear-fuel container is used as the research object. The technology of outside mold has been identified in the actual production process. Through physical simulation experiment, the thickness of the outside the chills can be determined, and the cooling effect of chills is verified. The results show that cooling conditions have a decisive effect on the eutectic solidification, the residence time of eutectic platform and the time of casting solidification.

Abstract: A commercial software, MAGMASOFT, was used to simulate the ZM5 shell with different materials of chills. The calculated results of solidification are obtained. Shrinkage porosity is predicted by means of a built-in porosity criterion. It shows that using the different materials of chills, such as copper, gray iron and steel, a large amount of shrinkage porosity defects are formed in ZM5 shell. However, with graphite as the material of chills, shrinkage porosity defects of ZM5 shell can be effectively reduced.

Abstract: In this work an analytical solution is used to explain the mechanism of dissolved sulfur influence on the transition from graphite to cementite eutectic in cast iron. It is found that this transition can be related to (1) the nucleation potential of graphite (characterized by nucleation coefficients, Ns and b (2) the growth rate coefficient of graphite eutectic cell,  (3) the temperature range, Tsc = Ts - Tc (where Ts and Tc is the equilibrium temperature of the graphite eutectic and the formation temperature of the cementite eutectic respectively) and (4) the liquid volume fraction, fl after solidification of the pre-eutectic austenite. It has been shown that the main impact of dissolved sulfur on the transition from graphite to cementite eutectic consists in reducing the growth rate of graphite eutectic cell. Analytical equations were presented to describe the absolute chilling tendency, CT, and the chill, w of cast iron. Finally, it has been shown that as dissolved sulfur content in cast iron increases, the eutectic cell count, N, the maximum degree of undercooling at the onset of graphite eutectic solidification, ∆Tm, and the chilling tendency index, CT and chill, w increase as well.