Effects of Coating Thickness and Pouring Temperature on Thermal Response in Lost Foam Casting

摘要

The accuracy of modeling any casting during solidification depends on the judicious assumption of the heat transfer coefficient at the mold-metal interface, h_i. In this research, a pioneering effort has been made for estimating h_i toward the end of solidification. Equations were derived to relate h_i with the characteristics of the cooling curve. A program has been developed to estimate h_i based on the cooling curve data. Additionally, fraction of solid, f_s, couldalso be obtained from the thermal analysis data. A program was developed to solve the inverse heat conduction problem for estimating h_i from the beginning of solidification until the onset of recalescence. Cylindrical castings were produced through lost foam casting process with three coating thicknesses and three pouring temperatures. Eight thermocouples were placed at various locations, six in the casting and two in the mold, and time-temperature data were obtained. The results obtained in this work indicate that h_i, at the beginning and at the end of solidification, decreases with increase in pouring temperature and increase in coating thickness. The trends in the f_s-temperature relationships were similar. The f_s at any temperature between the liquidus and solidus were found to increase with increasing coating thickness. This work is part of an ongoing study to develop an application-oriented method of evaluating coatings, and to develop heat transfer models of potential industrial application.