An optimization methodology for modeling the solidification of commercial gray and white iron.

摘要

This thesis concerns the development of a micro-model for hypoeutectic gray and white iron melts. The model has been coupled with heat transfer macromodels and utilized in conjunction with optimization methodology to analyze and interpret data acquired in two independent experimental programs. One set of experiments involved an investigation of the influence of riser sleeves on solidification time and the other a thermal analysis-based designed experiment to study the effect of carbon, silicon, phosphorus, manganese, and sulfur on the solidification characteristics of gray iron. In the case of the riser-sleeve application, the micro-model was coupled with a finite difference macromodel to simulate heat transfer and an optimization procedure was developed to estimate interfacial heat transfer coefficients applicable for select insulation and exothermic riser sleeves. In the thermal analysis application, the micro-model was coupled with a lumped system macro-model to determine values of the kinetics growth constant for primary austenite precipitation in hypoeutectic cast irons, carbide eutectic solidification in white irons, and graphite eutectic solidification in gray irons. In all cases it was observed that carbon and silicon were dominant main effects on {dollar}Ksb{lcub}A{rcub}{dollar} and {dollar}Ksb{lcub}E{rcub}{dollar} with the kinetics constant decreasing with increasing carbon and silicon. At fixed carbon and silicon melt chemistry, the magnitude of {dollar}Ksb{lcub}A{rcub}{dollar} and {dollar}Ksb{lcub}E{rcub}{dollar} for gray iron was approximately double that for white iron, with the white iron parameters being more sensitive to changes in carbon and silicon. Results concerning the chemistry dependence of the growth kinetics parameters for gray and white iron have not previously been published in the literature.