The transition from gray to white cast iron during solidification: Part II. Experimental verification

Abstract

In this work, an experimental verification for the transition theory from gray to white cast iron solidification is presented. Experimental tests have been implemented using plate-and wedge-shaped castings of various sizes. The experiments included inoculated and noninoculated cast irons of different chemical compositions and time-temperature histories of the inoculation effects. In addition, thermalanalysis tests were employed to determine the degree of undercooling of graphite eutectic (⌬T m ). This included microstructural evaluations in order to establish the eutectic-cell densities. This procedure enabled the calculation of the theoretical chill width (w), as well as the chilling tendency (CT) of cast iron. It was found that the predictions of the theoretical analysis are in good agreement with the experimental outcome for the chill exhibited in wedge-and plate-shaped castings.

Role of Alloying Additions in the Solidification Kinetics and Resultant Chilling Tendency and Chill of Cast Iron

“…The type, number and size of these substrates are in general influenced by numerous factors, including the chemistry of the cast iron, inoculation, charge materials, melt precondition [28], temperature, bath holding times, furnace atmosphere and the type of slags. In general, the number of nucleation sites from these substrates can be described by the following size distribution function [29]:…”

“…Thus, the number of active nucleation sites, N, is given by the area below the n(l) curve in lm  l   (0  T  Tm). Plugging Equation (31) into Equation (28) and integrating from lm to ∞, the second nucleation coefficient b is obtained:…”

Modeling and Simulation of the Gray-to-White Transition during Solidification of a Hypereutectic Gray Cast Iron: Application to a Stub-to-Carbon Connection Used in Smelting Processes

“…The chilling tendency (CT) of a given cast iron part, i.e., its susceptibility for the GWT, is a well-known index to determine its subsequent performance in diverse applications: high CT cast irons develop white or mottled regions with high hardness and excellent wear properties, whilst small CT cast irons favor the formation of gray zones with lower hardness and good machinability. Due to this, the effects of chemical composition and inoculation practice on the CT have been particularly addressed, both experimentally and theoretically ( [5][6][7][8][9], and references therein). Moreover, the influence of some alloying elements on the competition between the gray and white eutectics has been studied in directional solidification experiments by measuring the associated transition velocities [10,11].…”

Simulation of Heat Flow in Computational Method and Its Verification on the Structure and Property of Gray Cast Iron

“…If the heat-flow through the mould is very quick, the solidification rate will be high at that point and will affect the microstructure and properties of the materials. Heat-flow through the sand mould was studied by many researchers (Seetharamu et al, 2001;Pequet et al, 2002;Sulaiman and Hamouda, 2004;Mirbagheri et al, 2004;Lee and Lee, 2005;Kulkarni and Radhakrishna, 2007;Kermanpur et al, 2008;Hsu et al, 2009;Fras et al, 2005a;2005b;Collini et al, 2008). Seetharamu et al (2001) studied the solidification phenomena in sand mould for thermal stress using FEA and they discussed about the effect of solidification on stress formation in casting.…”

“…Hsu et al (2009) investigated on the multiple-gate runner system for gravity casting in sand mould in computational method. Fras et al (2005a;2005b) studied on the transition from gray to white during solidification for both mathematically and experimentally. They conclude that solidification rate depends on the modulus of the casting and the heat flow through the mould that is molding materials.…”