Procedure development to estimate the nodularity of cast iron using ultrasonic testing equipment

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Wabi Iron and Steel Corp. specialize in the design and development cast iron parts. Magnesium (Mg) is used as a spheroidizer inthe casting process. The amount of Mg in the melt determines the nodularity of the cast iron, which in turn determines themechanical properties of the casting. The present process involves the addition of Mg to the molten steel in ladle, far upstream inthe process. The challenge with this technique is that the Mg volatilizes from the ladle within a short period of time, thus, leading tolower nodularity from the beginning of the pour to the end hence, inferior mechanical properties of the casting. The current processof measuring the nodularity is through metallographic analysis by taking a sample from the ladle.The proposed solution to this problem is to change the casting process in order to add Mg to the steel at the time that it is pouredinto the individual molds. A preliminary literature review has identified research that show the feasibility of a non-destructive testmethod that would provide faster results for determining nodularity of cast iron through the measurement of the acoustic speed ofsound using ultrasonic sound waves. However, there is no data readily available for the type of casting alloy being used by WabiIron and Steel. This project proposes to use the pure research that has been done to develop a specific test method andexperimental data that correlates the nondestructive measurements with actual metallographic condition of the material.